[EE] Eliminating external noise through PS

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Re: [EE] Eliminating external noise through PS

Neil
I strongly feel so, because in my early tests, I:
(a) disconnected one of the pump wires (so the pump wouldn't run), and
it was (expectedly) very clean (on the scope).
(b) disconnected both of the pump wires and plugged it into the female
side of a PC power cord, so the pump ran, but was connected to 120VAC
from a different source.  Very clean power again.
In both cases, all else stayed the same including where the wires were
draped, etc.

In other tests, I moved the scope, power lines, etc and no change to the
noise on the line.

Either way, I haven't done my other tests yet since I took the pump with
me, so I'll get to those this week.

Cheers,
-Neil.


On 12/11/2020 7:37 PM, Jason White wrote:

> Hi Neil,
>
> This may be a silly question: are you sure that some of these voltage
> spikes that you've captured on the scope are not artifacts of your
> measurement setup? The loop formed by the ground wire/clip on a scope probe
> makes a very effective antenna. Maybe your power rail is cleaner than you
> think - in which case the true problem might be elsewhere.
>
> -Jason White
>
> On Fri, Dec 11, 2020 at 3:11 PM Neil <[hidden email]> wrote:
>
>> Sorry, disappeared for a couple days, but some quick answers to
>> everything for now, and my next steps:
>>
>> - Yes I have flyback diodes.   Highlighted with yellow here,  just above
>> the relays...
>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
>> - James & Russell, in that diagram also, I labeled the paths for power.
>> The 5V to the relays is pretty much dedicated and 5V is on the top
>> layer, and (dedicated) ground for the relays on the bottom layer.  But
>> yes, it's right up against the AC section, but as many components have
>> been removed now, I will push that far away.
>> - The 3.3V regulator has been getting a bit warmer than I like, so I
>> have been planning to use a buck converter instead.  But maybe I should
>> run two 3.3V regulators instead?  I would think that the buck converter
>> would be pass less of the noise through.
>> - I ran over there quickly to pick up stuff and tried a crude
>> (uncalculated) common-mode choke I made up from stuff I could find. Did
>> not make in dent in the noise coming through.
>> See here...
>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
>> - I feel like Brent may be correct, that the noise may be coming from
>> the relay side.  The processor (ESP32) is resetting.  I know it's not a
>> firmware issue as it had zero crashes with the previous pump.
>>
>>
>> Adding some info:
>> The previous pump was a huge AC pump.  This new pump is actually DC, but
>> there's a bridge rectifier on the wires.  So I'm now convinced that the
>> noise is coming from brushes.
>> I brought the pump with me, and I have a new blank board.  My plan is to
>> reproduce just enough of the circuit to see the noise, and I can cut and
>> re-route traces (the 5V & ground to the relays) to see if helps.
>> I will also add a ceramic capacitor to the pump wires (right at the
>> pump), and hope that helps.  Plus twist the wires.
>>
>> I'll be back with some results.
>>
>> Cheers,
>> -Neil.
>>
>>
>>
>> On 12/10/2020 7:28 PM, FTL wrote:
>>> This is almost too obvious, but in the schematic I do not see a flyback
>>> diode across the relay to suppress the back EMF when the relay is turned
>>> off. The lack of diode would cause a serious spike in the 5V supply when
>> the
>>> relay is turned off.
>>>
>>> Is the transistor being turned on hard enough to keep the relay on
>> properly.
>>> If it is not fully on with no flyback diode, maybe it is occasionally
>>> releasing and causing big noise on the 5V bus.
>>>
>>>> -----Original Message-----
>>>> From: [hidden email] <[hidden email]> On Behalf Of
>> Neil
>>>> Sent: December 8, 2020 11:04 AM
>>>> To: Microcontroller discussion list - Public. <[hidden email]>
>>>> Subject: [EE] Eliminating external noise through PS
>>>>
>>>> Hi,
>>>>
>>>> I'm working on a device that takes 120VAC, converts to 5VDC with a PCB-
>>>> mounted power supply, then further reduces that to 3.3VDC with a linear
>>>> regulator.
>>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
>>>> Overview...
>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
>>>>
>>>> All has been great until we switched to a specific pump, which happens
>> to
>>>> generate a LOT of conducted noise, which passes through the 5V PS, and
>> the
>>>> 3.3V regulator, and causing the microcontroller to crash.
>>>> I did a bunch of tested and found that the noise is being conducted
>>> through
>>>> the wires back to the board through the PS, through the linear
>> regulator,
>>> and
>>>> this is the 3.3V line...
>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
>>>>
>>>> I was over at someone else's place so did not have a lot of parts with
>> me,
>>>> but...
>>>> Adding a bunch more 0.1uf bypass capacitors all over the board did not
>>> help.
>>>> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the rate
>>> of
>>>> the crashing... but the ripple itself wasn't causing crashing.
>>>>
>>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC input
>>> wires
>>>> did not help.
>>>> I then tried to create a crude/uncalculated LC filter (which whatever
>>>> components I had on hand (33uh inductor and 1000uf capacitor, should be
>>>> low ESR), then a Pi filter (added 680 uF capacitor), and those barely
>> made
>>> a
>>>> dent.
>>>> Eventually I added another 0.1uf capacitor to the output side of the pi
>>> filter
>>>> and that helped enough to prevent the microcontroller crashing.
>>>> But there is still a lot of noise on the 3.3V line...
>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
>>>>
>>>> FWIW, this is where it ended up...
>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
>>>>
>>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
>>>> I feel like smaller, low-ESR ceramic caps should help, but I doubt it
>> will
>>> take
>>>> out most of the noise.
>>>> What is the right type of filter to eliminate this noise?
>>>>
>>>> Cheers,
>>>> -Neil.
>>>>
>>>> --
>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>> View/change your membership options at
>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>> --
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> http://mailman.mit.edu/mailman/listinfo/piclist
>>
>

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Re: [EE] Eliminating external noise through PS

Jason White-20
Neil, from the pictures it looks like you're using a 2 layer PCB. Have you
considered a 4 layer PCB? A continuous dedicated ground plane layer would
drastically reduce the loop area (and thus susceptibility to EMI) of your
traces.

Otherwise, it may be worth considering moving the relays to a separate
board/area.

On Sunday, December 13, 2020, Neil <[hidden email]> wrote:

> I strongly feel so, because in my early tests, I:
> (a) disconnected one of the pump wires (so the pump wouldn't run), and
> it was (expectedly) very clean (on the scope).
> (b) disconnected both of the pump wires and plugged it into the female
> side of a PC power cord, so the pump ran, but was connected to 120VAC
> from a different source.  Very clean power again.
> In both cases, all else stayed the same including where the wires were
> draped, etc.
>
> In other tests, I moved the scope, power lines, etc and no change to the
> noise on the line.
>
> Either way, I haven't done my other tests yet since I took the pump with
> me, so I'll get to those this week.
>
> Cheers,
> -Neil.
>
>
> On 12/11/2020 7:37 PM, Jason White wrote:
> > Hi Neil,
> >
> > This may be a silly question: are you sure that some of these voltage
> > spikes that you've captured on the scope are not artifacts of your
> > measurement setup? The loop formed by the ground wire/clip on a scope
> probe
> > makes a very effective antenna. Maybe your power rail is cleaner than you
> > think - in which case the true problem might be elsewhere.
> >
> > -Jason White
> >
> > On Fri, Dec 11, 2020 at 3:11 PM Neil <[hidden email]> wrote:
> >
> >> Sorry, disappeared for a couple days, but some quick answers to
> >> everything for now, and my next steps:
> >>
> >> - Yes I have flyback diodes.   Highlighted with yellow here,  just above
> >> the relays...
> >> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
> >> - James & Russell, in that diagram also, I labeled the paths for power.
> >> The 5V to the relays is pretty much dedicated and 5V is on the top
> >> layer, and (dedicated) ground for the relays on the bottom layer.  But
> >> yes, it's right up against the AC section, but as many components have
> >> been removed now, I will push that far away.
> >> - The 3.3V regulator has been getting a bit warmer than I like, so I
> >> have been planning to use a buck converter instead.  But maybe I should
> >> run two 3.3V regulators instead?  I would think that the buck converter
> >> would be pass less of the noise through.
> >> - I ran over there quickly to pick up stuff and tried a crude
> >> (uncalculated) common-mode choke I made up from stuff I could find. Did
> >> not make in dent in the noise coming through.
> >> See here...
> >> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
> >> - I feel like Brent may be correct, that the noise may be coming from
> >> the relay side.  The processor (ESP32) is resetting.  I know it's not a
> >> firmware issue as it had zero crashes with the previous pump.
> >>
> >>
> >> Adding some info:
> >> The previous pump was a huge AC pump.  This new pump is actually DC, but
> >> there's a bridge rectifier on the wires.  So I'm now convinced that the
> >> noise is coming from brushes.
> >> I brought the pump with me, and I have a new blank board.  My plan is to
> >> reproduce just enough of the circuit to see the noise, and I can cut and
> >> re-route traces (the 5V & ground to the relays) to see if helps.
> >> I will also add a ceramic capacitor to the pump wires (right at the
> >> pump), and hope that helps.  Plus twist the wires.
> >>
> >> I'll be back with some results.
> >>
> >> Cheers,
> >> -Neil.
> >>
> >>
> >>
> >> On 12/10/2020 7:28 PM, FTL wrote:
> >>> This is almost too obvious, but in the schematic I do not see a flyback
> >>> diode across the relay to suppress the back EMF when the relay is
> turned
> >>> off. The lack of diode would cause a serious spike in the 5V supply
> when
> >> the
> >>> relay is turned off.
> >>>
> >>> Is the transistor being turned on hard enough to keep the relay on
> >> properly.
> >>> If it is not fully on with no flyback diode, maybe it is occasionally
> >>> releasing and causing big noise on the 5V bus.
> >>>
> >>>> -----Original Message-----
> >>>> From: [hidden email] <[hidden email]> On Behalf Of
> >> Neil
> >>>> Sent: December 8, 2020 11:04 AM
> >>>> To: Microcontroller discussion list - Public. <[hidden email]>
> >>>> Subject: [EE] Eliminating external noise through PS
> >>>>
> >>>> Hi,
> >>>>
> >>>> I'm working on a device that takes 120VAC, converts to 5VDC with a
> PCB-
> >>>> mounted power supply, then further reduces that to 3.3VDC with a
> linear
> >>>> regulator.
> >>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
> >>>> Overview...
> >>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
> >>>>
> >>>> All has been great until we switched to a specific pump, which happens
> >> to
> >>>> generate a LOT of conducted noise, which passes through the 5V PS, and
> >> the
> >>>> 3.3V regulator, and causing the microcontroller to crash.
> >>>> I did a bunch of tested and found that the noise is being conducted
> >>> through
> >>>> the wires back to the board through the PS, through the linear
> >> regulator,
> >>> and
> >>>> this is the 3.3V line...
> >>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
> >>>>
> >>>> I was over at someone else's place so did not have a lot of parts with
> >> me,
> >>>> but...
> >>>> Adding a bunch more 0.1uf bypass capacitors all over the board did not
> >>> help.
> >>>> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
> >>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
> rate
> >>> of
> >>>> the crashing... but the ripple itself wasn't causing crashing.
> >>>>
> >>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC
> input
> >>> wires
> >>>> did not help.
> >>>> I then tried to create a crude/uncalculated LC filter (which whatever
> >>>> components I had on hand (33uh inductor and 1000uf capacitor, should
> be
> >>>> low ESR), then a Pi filter (added 680 uF capacitor), and those barely
> >> made
> >>> a
> >>>> dent.
> >>>> Eventually I added another 0.1uf capacitor to the output side of the
> pi
> >>> filter
> >>>> and that helped enough to prevent the microcontroller crashing.
> >>>> But there is still a lot of noise on the 3.3V line...
> >>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
> >>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
> >>>>
> >>>> FWIW, this is where it ended up...
> >>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
> >>>>
> >>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
> >>>> I feel like smaller, low-ESR ceramic caps should help, but I doubt it
> >> will
> >>> take
> >>>> out most of the noise.
> >>>> What is the right type of filter to eliminate this noise?
> >>>>
> >>>> Cheers,
> >>>> -Neil.
> >>>>
> >>>> --
> >>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> >>>> View/change your membership options at
> >>>> http://mailman.mit.edu/mailman/listinfo/piclist
> >> --
> >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> >> View/change your membership options at
> >> http://mailman.mit.edu/mailman/listinfo/piclist
> >>
> >
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>


--
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Re: [EE] Eliminating external noise through PS

Neil
That's a definite possibility at this point.  The original circuit
(prior version) worked great with 2 layers, but I needed 2oz copper to
handle the pump current.
Never version works just as great.  Or  I should say "worked", until
they decided to switch from the AC pump to this DC pump.

Cheers,
-Neil



On 12/13/2020 6:58 PM, Jason White wrote:

> Neil, from the pictures it looks like you're using a 2 layer PCB. Have you
> considered a 4 layer PCB? A continuous dedicated ground plane layer would
> drastically reduce the loop area (and thus susceptibility to EMI) of your
> traces.
>
> Otherwise, it may be worth considering moving the relays to a separate
> board/area.
>
> On Sunday, December 13, 2020, Neil <[hidden email]> wrote:
>
>> I strongly feel so, because in my early tests, I:
>> (a) disconnected one of the pump wires (so the pump wouldn't run), and
>> it was (expectedly) very clean (on the scope).
>> (b) disconnected both of the pump wires and plugged it into the female
>> side of a PC power cord, so the pump ran, but was connected to 120VAC
>> from a different source.  Very clean power again.
>> In both cases, all else stayed the same including where the wires were
>> draped, etc.
>>
>> In other tests, I moved the scope, power lines, etc and no change to the
>> noise on the line.
>>
>> Either way, I haven't done my other tests yet since I took the pump with
>> me, so I'll get to those this week.
>>
>> Cheers,
>> -Neil.
>>
>>
>> On 12/11/2020 7:37 PM, Jason White wrote:
>>> Hi Neil,
>>>
>>> This may be a silly question: are you sure that some of these voltage
>>> spikes that you've captured on the scope are not artifacts of your
>>> measurement setup? The loop formed by the ground wire/clip on a scope
>> probe
>>> makes a very effective antenna. Maybe your power rail is cleaner than you
>>> think - in which case the true problem might be elsewhere.
>>>
>>> -Jason White
>>>
>>> On Fri, Dec 11, 2020 at 3:11 PM Neil <[hidden email]> wrote:
>>>
>>>> Sorry, disappeared for a couple days, but some quick answers to
>>>> everything for now, and my next steps:
>>>>
>>>> - Yes I have flyback diodes.   Highlighted with yellow here,  just above
>>>> the relays...
>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
>>>> - James & Russell, in that diagram also, I labeled the paths for power.
>>>> The 5V to the relays is pretty much dedicated and 5V is on the top
>>>> layer, and (dedicated) ground for the relays on the bottom layer.  But
>>>> yes, it's right up against the AC section, but as many components have
>>>> been removed now, I will push that far away.
>>>> - The 3.3V regulator has been getting a bit warmer than I like, so I
>>>> have been planning to use a buck converter instead.  But maybe I should
>>>> run two 3.3V regulators instead?  I would think that the buck converter
>>>> would be pass less of the noise through.
>>>> - I ran over there quickly to pick up stuff and tried a crude
>>>> (uncalculated) common-mode choke I made up from stuff I could find. Did
>>>> not make in dent in the noise coming through.
>>>> See here...
>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
>>>> - I feel like Brent may be correct, that the noise may be coming from
>>>> the relay side.  The processor (ESP32) is resetting.  I know it's not a
>>>> firmware issue as it had zero crashes with the previous pump.
>>>>
>>>>
>>>> Adding some info:
>>>> The previous pump was a huge AC pump.  This new pump is actually DC, but
>>>> there's a bridge rectifier on the wires.  So I'm now convinced that the
>>>> noise is coming from brushes.
>>>> I brought the pump with me, and I have a new blank board.  My plan is to
>>>> reproduce just enough of the circuit to see the noise, and I can cut and
>>>> re-route traces (the 5V & ground to the relays) to see if helps.
>>>> I will also add a ceramic capacitor to the pump wires (right at the
>>>> pump), and hope that helps.  Plus twist the wires.
>>>>
>>>> I'll be back with some results.
>>>>
>>>> Cheers,
>>>> -Neil.
>>>>
>>>>
>>>>
>>>> On 12/10/2020 7:28 PM, FTL wrote:
>>>>> This is almost too obvious, but in the schematic I do not see a flyback
>>>>> diode across the relay to suppress the back EMF when the relay is
>> turned
>>>>> off. The lack of diode would cause a serious spike in the 5V supply
>> when
>>>> the
>>>>> relay is turned off.
>>>>>
>>>>> Is the transistor being turned on hard enough to keep the relay on
>>>> properly.
>>>>> If it is not fully on with no flyback diode, maybe it is occasionally
>>>>> releasing and causing big noise on the 5V bus.
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: [hidden email] <[hidden email]> On Behalf Of
>>>> Neil
>>>>>> Sent: December 8, 2020 11:04 AM
>>>>>> To: Microcontroller discussion list - Public. <[hidden email]>
>>>>>> Subject: [EE] Eliminating external noise through PS
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> I'm working on a device that takes 120VAC, converts to 5VDC with a
>> PCB-
>>>>>> mounted power supply, then further reduces that to 3.3VDC with a
>> linear
>>>>>> regulator.
>>>>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
>>>>>> Overview...
>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
>>>>>>
>>>>>> All has been great until we switched to a specific pump, which happens
>>>> to
>>>>>> generate a LOT of conducted noise, which passes through the 5V PS, and
>>>> the
>>>>>> 3.3V regulator, and causing the microcontroller to crash.
>>>>>> I did a bunch of tested and found that the noise is being conducted
>>>>> through
>>>>>> the wires back to the board through the PS, through the linear
>>>> regulator,
>>>>> and
>>>>>> this is the 3.3V line...
>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
>>>>>>
>>>>>> I was over at someone else's place so did not have a lot of parts with
>>>> me,
>>>>>> but...
>>>>>> Adding a bunch more 0.1uf bypass capacitors all over the board did not
>>>>> help.
>>>>>> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
>>>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
>> rate
>>>>> of
>>>>>> the crashing... but the ripple itself wasn't causing crashing.
>>>>>>
>>>>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC
>> input
>>>>> wires
>>>>>> did not help.
>>>>>> I then tried to create a crude/uncalculated LC filter (which whatever
>>>>>> components I had on hand (33uh inductor and 1000uf capacitor, should
>> be
>>>>>> low ESR), then a Pi filter (added 680 uF capacitor), and those barely
>>>> made
>>>>> a
>>>>>> dent.
>>>>>> Eventually I added another 0.1uf capacitor to the output side of the
>> pi
>>>>> filter
>>>>>> and that helped enough to prevent the microcontroller crashing.
>>>>>> But there is still a lot of noise on the 3.3V line...
>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
>>>>>>
>>>>>> FWIW, this is where it ended up...
>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
>>>>>>
>>>>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
>>>>>> I feel like smaller, low-ESR ceramic caps should help, but I doubt it
>>>> will
>>>>> take
>>>>>> out most of the noise.
>>>>>> What is the right type of filter to eliminate this noise?
>>>>>>
>>>>>> Cheers,
>>>>>> -Neil.
>>>>>>
>>>>>> --
>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>>> View/change your membership options at
>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>> --
>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>> View/change your membership options at
>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>>
>> --
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> http://mailman.mit.edu/mailman/listinfo/piclist
>>
>

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Re: [EE] Eliminating external noise through PS

Neil
Happy holidays everyone.

Okay, I got back to this recently and have a bunch of updates:

For the tl;dr 'ers... I've got a lot of noise out, the processor does
not crash anymore, but 2 questions remain:

- Should I have the AC-outlet ground wire, coming onto the PCB and used
as a shield?

- If I hold the AC wire with my hand, the noise (as seen on the
oscilloscope) drops (noticeably).  Shielding the AC wire does not have
the same effect, so what is happening here, and how can I use this to
help reduce the noise even more?


For the gory details, here's my summary of what I tried and found...

For reference...
http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
noise is mostly in the few Mhz range and higher.

- Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
- Low-pass filter helped minimally
- Pi filter was a bit better, but still small impact.
- Common mode choke (uncalculated, but should've been able to separate
60Hz from Mhz-range noise) didn't help.  I am new to these, but
apparently above some frequency the impedance drops again.
- Ferrite across AC side of motor wires helped minimally.
- Ferrite on incoming-power AC wires did not help
- Removed relay (and jumper across contacts to run the pump) to see if
noise was coming into board from that side, but nope.
- Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
with wires soldered on for the incoming power and parallel wires to run
the pump, and a 1k load resistor on the PS output. Still a lot of noise
- Low-pass filter again helped reduce noise minimally.
- Capacitance multiplier helped noticeably.
- 2 more ceramic caps from each motor wire to ground/motor case (right
at the motor) helped noticeably.
- Twisted the AC wires to the motor tighter, and didn't really see any
difference.
- Back to original board, to use some of these, but too much voltage
drop on capacitance multiplier to be usable.  I should calculate this
properly and find the right transistor for this.

At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
filter and the board isn't crashing, but I can still see some noise on
the scope, which I'd like to reduce even more.  Going to try a
multi-stage pi/LC filter.

But I'm curious how to use the "phenomenon" where holding the AC wire in
my hand reduces noise noticeably, to help this.


Thanks,
-Neil.



On 12/13/2020 7:15 PM, Neil wrote:

> That's a definite possibility at this point.  The original circuit
> (prior version) worked great with 2 layers, but I needed 2oz copper to
> handle the pump current.
> Never version works just as great.  Or  I should say "worked", until
> they decided to switch from the AC pump to this DC pump.
>
> Cheers,
> -Neil
>
>
>
> On 12/13/2020 6:58 PM, Jason White wrote:
>> Neil, from the pictures it looks like you're using a 2 layer PCB. Have you
>> considered a 4 layer PCB? A continuous dedicated ground plane layer would
>> drastically reduce the loop area (and thus susceptibility to EMI) of your
>> traces.
>>
>> Otherwise, it may be worth considering moving the relays to a separate
>> board/area.
>>
>> On Sunday, December 13, 2020, Neil <[hidden email]> wrote:
>>
>>> I strongly feel so, because in my early tests, I:
>>> (a) disconnected one of the pump wires (so the pump wouldn't run), and
>>> it was (expectedly) very clean (on the scope).
>>> (b) disconnected both of the pump wires and plugged it into the female
>>> side of a PC power cord, so the pump ran, but was connected to 120VAC
>>> from a different source.  Very clean power again.
>>> In both cases, all else stayed the same including where the wires were
>>> draped, etc.
>>>
>>> In other tests, I moved the scope, power lines, etc and no change to the
>>> noise on the line.
>>>
>>> Either way, I haven't done my other tests yet since I took the pump with
>>> me, so I'll get to those this week.
>>>
>>> Cheers,
>>> -Neil.
>>>
>>>
>>> On 12/11/2020 7:37 PM, Jason White wrote:
>>>> Hi Neil,
>>>>
>>>> This may be a silly question: are you sure that some of these voltage
>>>> spikes that you've captured on the scope are not artifacts of your
>>>> measurement setup? The loop formed by the ground wire/clip on a scope
>>> probe
>>>> makes a very effective antenna. Maybe your power rail is cleaner than you
>>>> think - in which case the true problem might be elsewhere.
>>>>
>>>> -Jason White
>>>>
>>>> On Fri, Dec 11, 2020 at 3:11 PM Neil <[hidden email]> wrote:
>>>>
>>>>> Sorry, disappeared for a couple days, but some quick answers to
>>>>> everything for now, and my next steps:
>>>>>
>>>>> - Yes I have flyback diodes.   Highlighted with yellow here,  just above
>>>>> the relays...
>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
>>>>> - James & Russell, in that diagram also, I labeled the paths for power.
>>>>> The 5V to the relays is pretty much dedicated and 5V is on the top
>>>>> layer, and (dedicated) ground for the relays on the bottom layer.  But
>>>>> yes, it's right up against the AC section, but as many components have
>>>>> been removed now, I will push that far away.
>>>>> - The 3.3V regulator has been getting a bit warmer than I like, so I
>>>>> have been planning to use a buck converter instead.  But maybe I should
>>>>> run two 3.3V regulators instead?  I would think that the buck converter
>>>>> would be pass less of the noise through.
>>>>> - I ran over there quickly to pick up stuff and tried a crude
>>>>> (uncalculated) common-mode choke I made up from stuff I could find. Did
>>>>> not make in dent in the noise coming through.
>>>>> See here...
>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
>>>>> - I feel like Brent may be correct, that the noise may be coming from
>>>>> the relay side.  The processor (ESP32) is resetting.  I know it's not a
>>>>> firmware issue as it had zero crashes with the previous pump.
>>>>>
>>>>>
>>>>> Adding some info:
>>>>> The previous pump was a huge AC pump.  This new pump is actually DC, but
>>>>> there's a bridge rectifier on the wires.  So I'm now convinced that the
>>>>> noise is coming from brushes.
>>>>> I brought the pump with me, and I have a new blank board.  My plan is to
>>>>> reproduce just enough of the circuit to see the noise, and I can cut and
>>>>> re-route traces (the 5V & ground to the relays) to see if helps.
>>>>> I will also add a ceramic capacitor to the pump wires (right at the
>>>>> pump), and hope that helps.  Plus twist the wires.
>>>>>
>>>>> I'll be back with some results.
>>>>>
>>>>> Cheers,
>>>>> -Neil.
>>>>>
>>>>>
>>>>>
>>>>> On 12/10/2020 7:28 PM, FTL wrote:
>>>>>> This is almost too obvious, but in the schematic I do not see a flyback
>>>>>> diode across the relay to suppress the back EMF when the relay is
>>> turned
>>>>>> off. The lack of diode would cause a serious spike in the 5V supply
>>> when
>>>>> the
>>>>>> relay is turned off.
>>>>>>
>>>>>> Is the transistor being turned on hard enough to keep the relay on
>>>>> properly.
>>>>>> If it is not fully on with no flyback diode, maybe it is occasionally
>>>>>> releasing and causing big noise on the 5V bus.
>>>>>>
>>>>>>> -----Original Message-----
>>>>>>> From: [hidden email] <[hidden email]> On Behalf Of
>>>>> Neil
>>>>>>> Sent: December 8, 2020 11:04 AM
>>>>>>> To: Microcontroller discussion list - Public. <[hidden email]>
>>>>>>> Subject: [EE] Eliminating external noise through PS
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> I'm working on a device that takes 120VAC, converts to 5VDC with a
>>> PCB-
>>>>>>> mounted power supply, then further reduces that to 3.3VDC with a
>>> linear
>>>>>>> regulator.
>>>>>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
>>>>>>> Overview...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
>>>>>>>
>>>>>>> All has been great until we switched to a specific pump, which happens
>>>>> to
>>>>>>> generate a LOT of conducted noise, which passes through the 5V PS, and
>>>>> the
>>>>>>> 3.3V regulator, and causing the microcontroller to crash.
>>>>>>> I did a bunch of tested and found that the noise is being conducted
>>>>>> through
>>>>>>> the wires back to the board through the PS, through the linear
>>>>> regulator,
>>>>>> and
>>>>>>> this is the 3.3V line...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
>>>>>>>
>>>>>>> I was over at someone else's place so did not have a lot of parts with
>>>>> me,
>>>>>>> but...
>>>>>>> Adding a bunch more 0.1uf bypass capacitors all over the board did not
>>>>>> help.
>>>>>>> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
>>>>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
>>> rate
>>>>>> of
>>>>>>> the crashing... but the ripple itself wasn't causing crashing.
>>>>>>>
>>>>>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC
>>> input
>>>>>> wires
>>>>>>> did not help.
>>>>>>> I then tried to create a crude/uncalculated LC filter (which whatever
>>>>>>> components I had on hand (33uh inductor and 1000uf capacitor, should
>>> be
>>>>>>> low ESR), then a Pi filter (added 680 uF capacitor), and those barely
>>>>> made
>>>>>> a
>>>>>>> dent.
>>>>>>> Eventually I added another 0.1uf capacitor to the output side of the
>>> pi
>>>>>> filter
>>>>>>> and that helped enough to prevent the microcontroller crashing.
>>>>>>> But there is still a lot of noise on the 3.3V line...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
>>>>>>>
>>>>>>> FWIW, this is where it ended up...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
>>>>>>>
>>>>>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
>>>>>>> I feel like smaller, low-ESR ceramic caps should help, but I doubt it
>>>>> will
>>>>>> take
>>>>>>> out most of the noise.
>>>>>>> What is the right type of filter to eliminate this noise?
>>>>>>>
>>>>>>> Cheers,
>>>>>>> -Neil.
>>>>>>>
>>>>>>> --
>>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>>>> View/change your membership options at
>>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>>> --
>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>> View/change your membership options at
>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>>>
>>> --
>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>> View/change your membership options at
>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>

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Re: [EE] Eliminating external noise through PS

Jason White-20
My experience developing "all discrete" (no microcontroller) motor driver
PCBs is that any noise that is unaffected by filtering tends to be a
measurement or environmental artifact.

I'd recommend doubled checking your probe/scope grounding - it is an
endless source of trouble and erroneous readings. I've found that often
times problems in systems are a result of a combination of "innocent
looking" and unrelated things that end up interacting in unexpected ways.

On Tuesday, December 29, 2020, Neil <[hidden email]> wrote:

> Happy holidays everyone.
>
> Okay, I got back to this recently and have a bunch of updates:
>
> For the tl;dr 'ers... I've got a lot of noise out, the processor does
> not crash anymore, but 2 questions remain:
>
> - Should I have the AC-outlet ground wire, coming onto the PCB and used
> as a shield?
>
> - If I hold the AC wire with my hand, the noise (as seen on the
> oscilloscope) drops (noticeably).  Shielding the AC wire does not have
> the same effect, so what is happening here, and how can I use this to
> help reduce the noise even more?
>
>
> For the gory details, here's my summary of what I tried and found...
>
> For reference...
> http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
> noise is mostly in the few Mhz range and higher.
>
> - Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
> - Low-pass filter helped minimally
> - Pi filter was a bit better, but still small impact.
> - Common mode choke (uncalculated, but should've been able to separate
> 60Hz from Mhz-range noise) didn't help.  I am new to these, but
> apparently above some frequency the impedance drops again.
> - Ferrite across AC side of motor wires helped minimally.
> - Ferrite on incoming-power AC wires did not help
> - Removed relay (and jumper across contacts to run the pump) to see if
> noise was coming into board from that side, but nope.
> - Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
> with wires soldered on for the incoming power and parallel wires to run
> the pump, and a 1k load resistor on the PS output. Still a lot of noise
> - Low-pass filter again helped reduce noise minimally.
> - Capacitance multiplier helped noticeably.
> - 2 more ceramic caps from each motor wire to ground/motor case (right
> at the motor) helped noticeably.
> - Twisted the AC wires to the motor tighter, and didn't really see any
> difference.
> - Back to original board, to use some of these, but too much voltage
> drop on capacitance multiplier to be usable.  I should calculate this
> properly and find the right transistor for this.
>
> At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
> filter and the board isn't crashing, but I can still see some noise on
> the scope, which I'd like to reduce even more.  Going to try a
> multi-stage pi/LC filter.
>
> But I'm curious how to use the "phenomenon" where holding the AC wire in
> my hand reduces noise noticeably, to help this.
>
>
> Thanks,
> -Neil.
>
>
>
> On 12/13/2020 7:15 PM, Neil wrote:
> > That's a definite possibility at this point.  The original circuit
> > (prior version) worked great with 2 layers, but I needed 2oz copper to
> > handle the pump current.
> > Never version works just as great.  Or  I should say "worked", until
> > they decided to switch from the AC pump to this DC pump.
> >
> > Cheers,
> > -Neil
> >
> >
> >
> > On 12/13/2020 6:58 PM, Jason White wrote:
> >> Neil, from the pictures it looks like you're using a 2 layer PCB. Have
> you
> >> considered a 4 layer PCB? A continuous dedicated ground plane layer
> would
> >> drastically reduce the loop area (and thus susceptibility to EMI) of
> your
> >> traces.
> >>
> >> Otherwise, it may be worth considering moving the relays to a separate
> >> board/area.
> >>
> >> On Sunday, December 13, 2020, Neil <[hidden email]> wrote:
> >>
> >>> I strongly feel so, because in my early tests, I:
> >>> (a) disconnected one of the pump wires (so the pump wouldn't run), and
> >>> it was (expectedly) very clean (on the scope).
> >>> (b) disconnected both of the pump wires and plugged it into the female
> >>> side of a PC power cord, so the pump ran, but was connected to 120VAC
> >>> from a different source.  Very clean power again.
> >>> In both cases, all else stayed the same including where the wires were
> >>> draped, etc.
> >>>
> >>> In other tests, I moved the scope, power lines, etc and no change to
> the
> >>> noise on the line.
> >>>
> >>> Either way, I haven't done my other tests yet since I took the pump
> with
> >>> me, so I'll get to those this week.
> >>>
> >>> Cheers,
> >>> -Neil.
> >>>
> >>>
> >>> On 12/11/2020 7:37 PM, Jason White wrote:
> >>>> Hi Neil,
> >>>>
> >>>> This may be a silly question: are you sure that some of these voltage
> >>>> spikes that you've captured on the scope are not artifacts of your
> >>>> measurement setup? The loop formed by the ground wire/clip on a scope
> >>> probe
> >>>> makes a very effective antenna. Maybe your power rail is cleaner than
> you
> >>>> think - in which case the true problem might be elsewhere.
> >>>>
> >>>> -Jason White
> >>>>
> >>>> On Fri, Dec 11, 2020 at 3:11 PM Neil <[hidden email]> wrote:
> >>>>
> >>>>> Sorry, disappeared for a couple days, but some quick answers to
> >>>>> everything for now, and my next steps:
> >>>>>
> >>>>> - Yes I have flyback diodes.   Highlighted with yellow here,  just
> above
> >>>>> the relays...
> >>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
> >>>>> - James & Russell, in that diagram also, I labeled the paths for
> power.
> >>>>> The 5V to the relays is pretty much dedicated and 5V is on the top
> >>>>> layer, and (dedicated) ground for the relays on the bottom layer.
> But
> >>>>> yes, it's right up against the AC section, but as many components
> have
> >>>>> been removed now, I will push that far away.
> >>>>> - The 3.3V regulator has been getting a bit warmer than I like, so I
> >>>>> have been planning to use a buck converter instead.  But maybe I
> should
> >>>>> run two 3.3V regulators instead?  I would think that the buck
> converter
> >>>>> would be pass less of the noise through.
> >>>>> - I ran over there quickly to pick up stuff and tried a crude
> >>>>> (uncalculated) common-mode choke I made up from stuff I could find.
> Did
> >>>>> not make in dent in the noise coming through.
> >>>>> See here...
> >>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
> >>>>> - I feel like Brent may be correct, that the noise may be coming from
> >>>>> the relay side.  The processor (ESP32) is resetting.  I know it's
> not a
> >>>>> firmware issue as it had zero crashes with the previous pump.
> >>>>>
> >>>>>
> >>>>> Adding some info:
> >>>>> The previous pump was a huge AC pump.  This new pump is actually DC,
> but
> >>>>> there's a bridge rectifier on the wires.  So I'm now convinced that
> the
> >>>>> noise is coming from brushes.
> >>>>> I brought the pump with me, and I have a new blank board.  My plan
> is to
> >>>>> reproduce just enough of the circuit to see the noise, and I can cut
> and
> >>>>> re-route traces (the 5V & ground to the relays) to see if helps.
> >>>>> I will also add a ceramic capacitor to the pump wires (right at the
> >>>>> pump), and hope that helps.  Plus twist the wires.
> >>>>>
> >>>>> I'll be back with some results.
> >>>>>
> >>>>> Cheers,
> >>>>> -Neil.
> >>>>>
> >>>>>
> >>>>>
> >>>>> On 12/10/2020 7:28 PM, FTL wrote:
> >>>>>> This is almost too obvious, but in the schematic I do not see a
> flyback
> >>>>>> diode across the relay to suppress the back EMF when the relay is
> >>> turned
> >>>>>> off. The lack of diode would cause a serious spike in the 5V supply
> >>> when
> >>>>> the
> >>>>>> relay is turned off.
> >>>>>>
> >>>>>> Is the transistor being turned on hard enough to keep the relay on
> >>>>> properly.
> >>>>>> If it is not fully on with no flyback diode, maybe it is
> occasionally
> >>>>>> releasing and causing big noise on the 5V bus.
> >>>>>>
> >>>>>>> -----Original Message-----
> >>>>>>> From: [hidden email] <[hidden email]> On Behalf
> Of
> >>>>> Neil
> >>>>>>> Sent: December 8, 2020 11:04 AM
> >>>>>>> To: Microcontroller discussion list - Public. <[hidden email]>
> >>>>>>> Subject: [EE] Eliminating external noise through PS
> >>>>>>>
> >>>>>>> Hi,
> >>>>>>>
> >>>>>>> I'm working on a device that takes 120VAC, converts to 5VDC with a
> >>> PCB-
> >>>>>>> mounted power supply, then further reduces that to 3.3VDC with a
> >>> linear
> >>>>>>> regulator.
> >>>>>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
> >>>>>>> Overview...
> >>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
> >>>>>>>
> >>>>>>> All has been great until we switched to a specific pump, which
> happens
> >>>>> to
> >>>>>>> generate a LOT of conducted noise, which passes through the 5V PS,
> and
> >>>>> the
> >>>>>>> 3.3V regulator, and causing the microcontroller to crash.
> >>>>>>> I did a bunch of tested and found that the noise is being conducted
> >>>>>> through
> >>>>>>> the wires back to the board through the PS, through the linear
> >>>>> regulator,
> >>>>>> and
> >>>>>>> this is the 3.3V line...
> >>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
> >>>>>>>
> >>>>>>> I was over at someone else's place so did not have a lot of parts
> with
> >>>>> me,
> >>>>>>> but...
> >>>>>>> Adding a bunch more 0.1uf bypass capacitors all over the board did
> not
> >>>>>> help.
> >>>>>>> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
> >>>>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
> >>> rate
> >>>>>> of
> >>>>>>> the crashing... but the ripple itself wasn't causing crashing.
> >>>>>>>
> >>>>>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC
> >>> input
> >>>>>> wires
> >>>>>>> did not help.
> >>>>>>> I then tried to create a crude/uncalculated LC filter (which
> whatever
> >>>>>>> components I had on hand (33uh inductor and 1000uf capacitor,
> should
> >>> be
> >>>>>>> low ESR), then a Pi filter (added 680 uF capacitor), and those
> barely
> >>>>> made
> >>>>>> a
> >>>>>>> dent.
> >>>>>>> Eventually I added another 0.1uf capacitor to the output side of
> the
> >>> pi
> >>>>>> filter
> >>>>>>> and that helped enough to prevent the microcontroller crashing.
> >>>>>>> But there is still a lot of noise on the 3.3V line...
> >>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
> >>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
> >>>>>>>
> >>>>>>> FWIW, this is where it ended up...
> >>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
> >>>>>>>
> >>>>>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
> >>>>>>> I feel like smaller, low-ESR ceramic caps should help, but I doubt
> it
> >>>>> will
> >>>>>> take
> >>>>>>> out most of the noise.
> >>>>>>> What is the right type of filter to eliminate this noise?
> >>>>>>>
> >>>>>>> Cheers,
> >>>>>>> -Neil.
> >>>>>>>
> >>>>>>> --
> >>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> >>>>>>> View/change your membership options at
> >>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
> >>>>> --
> >>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> >>>>> View/change your membership options at
> >>>>> http://mailman.mit.edu/mailman/listinfo/piclist
> >>>>>
> >>> --
> >>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> >>> View/change your membership options at
> >>> http://mailman.mit.edu/mailman/listinfo/piclist
> >>>
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>


--
Jason White
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Re: [EE] Eliminating external noise through PS

madscientistatlarge
When you measure with the scope, how are you grounding the Probe?  Those convenient wires with alligator clips make good antennas, best to take a wire, preferably beryllium copper because it's springy, and wrap one end around the exposed ground just behind the tip, then bend it to point the same way as the signal probe and trim to length so you are grounding it right where you are measuring.  Might also want to float the scope to avoid ground loops.  If you are in the U.S. These guys will sell a single foot of beryllium copper wire, <http://lfa-wire.com/Plated-Wire-article/Plated-Wire-2.html>.  Haven't dealt with them but plan to as soon as I get my bench setup.  I learned this trick on a job and have seen it mentioned once online (been online since 2000).  In a pinch a piece of copper might work briefly, or any other stiff wire, possibly even a paper clip in a pinch (haven't tried it, steel does have some resistance but likely not too bad on 1cm or less).  When you cut the wire you can cut a nice point on the end.

Noise will drive one batty, I once traced it to a leaky transformer in a flow controller.  The current was going to ground through the computer's data acq card and sporadically making noise on the measurement.   No permanent effect in that case.  Thing was when I connected the scope ground to the equipment it took the leakage and the noise went away, only saw it because I reasoned the scope was doing the magic.  Opened the flow controller case and out of 4 transformers (1 for each channel) one had a big bubble on the encapsulation, I've always assumed it was spike damage.  Replaced the transformer and away went the noise.  The annoying thing is it had been in to the manufacturer for the noise problem and of course they found no issues (I don't blame them, I spent a day and a half playing with it before I figured it out).

When you grab the lead and the noise drops you're probably being a lossy load, or getting phase cancellation, or???  In a pinch you could use shielded wiring to the motor, conduit might help enough, preferably grounded at only the motor (noise source) end of the line.  Also unless your' filters are shielded, and the line to/from them noise can easily couple around the filter.  This happens with power entry filtering if the wires run near each other, which makes the packaged power entry filters worth the extra $$ in many cases.


Sent with ProtonMail Secure Email.

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Tuesday, December 29, 2020 12:36 PM, Jason White <[hidden email]> wrote:

> My experience developing "all discrete" (no microcontroller) motor driver
> PCBs is that any noise that is unaffected by filtering tends to be a
> measurement or environmental artifact.
>
> I'd recommend doubled checking your probe/scope grounding - it is an
> endless source of trouble and erroneous readings. I've found that often
> times problems in systems are a result of a combination of "innocent
> looking" and unrelated things that end up interacting in unexpected ways.
>
> On Tuesday, December 29, 2020, Neil [hidden email] wrote:
>
> > Happy holidays everyone.
> > Okay, I got back to this recently and have a bunch of updates:
> > For the tl;dr 'ers... I've got a lot of noise out, the processor does
> > not crash anymore, but 2 questions remain:
> >
> > -   Should I have the AC-outlet ground wire, coming onto the PCB and used
> >     as a shield?
> >
> > -   If I hold the AC wire with my hand, the noise (as seen on the
> >     oscilloscope) drops (noticeably). Shielding the AC wire does not have
> >     the same effect, so what is happening here, and how can I use this to
> >     help reduce the noise even more?
> >
> >
> > For the gory details, here's my summary of what I tried and found...
> > For reference...
> > http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
> > noise is mostly in the few Mhz range and higher.
> >
> > -   Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
> > -   Low-pass filter helped minimally
> > -   Pi filter was a bit better, but still small impact.
> > -   Common mode choke (uncalculated, but should've been able to separate
> >     60Hz from Mhz-range noise) didn't help. I am new to these, but
> >     apparently above some frequency the impedance drops again.
> >
> > -   Ferrite across AC side of motor wires helped minimally.
> > -   Ferrite on incoming-power AC wires did not help
> > -   Removed relay (and jumper across contacts to run the pump) to see if
> >     noise was coming into board from that side, but nope.
> >
> > -   Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
> >     with wires soldered on for the incoming power and parallel wires to run
> >     the pump, and a 1k load resistor on the PS output. Still a lot of noise
> >
> > -   Low-pass filter again helped reduce noise minimally.
> > -   Capacitance multiplier helped noticeably.
> > -   2 more ceramic caps from each motor wire to ground/motor case (right
> >     at the motor) helped noticeably.
> >
> > -   Twisted the AC wires to the motor tighter, and didn't really see any
> >     difference.
> >
> > -   Back to original board, to use some of these, but too much voltage
> >     drop on capacitance multiplier to be usable. I should calculate this
> >     properly and find the right transistor for this.
> >
> >
> > At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
> > filter and the board isn't crashing, but I can still see some noise on
> > the scope, which I'd like to reduce even more. Going to try a
> > multi-stage pi/LC filter.
> > But I'm curious how to use the "phenomenon" where holding the AC wire in
> > my hand reduces noise noticeably, to help this.
> > Thanks,
> > -Neil.
> > On 12/13/2020 7:15 PM, Neil wrote:
> >
> > > That's a definite possibility at this point. The original circuit
> > > (prior version) worked great with 2 layers, but I needed 2oz copper to
> > > handle the pump current.
> > > Never version works just as great. Or I should say "worked", until
> > > they decided to switch from the AC pump to this DC pump.
> > > Cheers,
> > > -Neil
> > > On 12/13/2020 6:58 PM, Jason White wrote:
> > >
> > > > Neil, from the pictures it looks like you're using a 2 layer PCB. Have
> > > > you
> > >
> > > > considered a 4 layer PCB? A continuous dedicated ground plane layer
> > > > would
> > >
> > > > drastically reduce the loop area (and thus susceptibility to EMI) of
> > > > your
> > >
> > > > traces.
> > > > Otherwise, it may be worth considering moving the relays to a separate
> > > > board/area.
> > > > On Sunday, December 13, 2020, Neil [hidden email] wrote:
> > > >
> > > > > I strongly feel so, because in my early tests, I:
> > > > > (a) disconnected one of the pump wires (so the pump wouldn't run), and
> > > > > it was (expectedly) very clean (on the scope).
> > > > > (b) disconnected both of the pump wires and plugged it into the female
> > > > > side of a PC power cord, so the pump ran, but was connected to 120VAC
> > > > > from a different source. Very clean power again.
> > > > > In both cases, all else stayed the same including where the wires were
> > > > > draped, etc.
> > > > > In other tests, I moved the scope, power lines, etc and no change to
> > > > > the
> > >
> > > > > noise on the line.
> > > > > Either way, I haven't done my other tests yet since I took the pump
> > > > > with
> > >
> > > > > me, so I'll get to those this week.
> > > > > Cheers,
> > > > > -Neil.
> > > > > On 12/11/2020 7:37 PM, Jason White wrote:
> > > > >
> > > > > > Hi Neil,
> > > > > > This may be a silly question: are you sure that some of these voltage
> > > > > > spikes that you've captured on the scope are not artifacts of your
> > > > > > measurement setup? The loop formed by the ground wire/clip on a scope
> > > > > > probe
> > > > > > makes a very effective antenna. Maybe your power rail is cleaner than
> > > > > > you
> > >
> > > > > > think - in which case the true problem might be elsewhere.
> > > > > > -Jason White
> > > > > > On Fri, Dec 11, 2020 at 3:11 PM Neil [hidden email] wrote:
> > > > > >
> > > > > > > Sorry, disappeared for a couple days, but some quick answers to
> > > > > > > everything for now, and my next steps:
> > > > > > >
> > > > > > > -   Yes I have flyback diodes. Highlighted with yellow here, just
> > > > > > >     above
> > > > > > >
> > >
> > > > > > > the relays...
> > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
> > > > > > >
> > > > > > > -   James & Russell, in that diagram also, I labeled the paths for
> > > > > > >     power.
> > > > > > >
> > >
> > > > > > > The 5V to the relays is pretty much dedicated and 5V is on the top
> > > > > > > layer, and (dedicated) ground for the relays on the bottom layer.
> > > > > > > But
> > >
> > > > > > > yes, it's right up against the AC section, but as many components
> > > > > > > have
> > >
> > > > > > > been removed now, I will push that far away.
> > > > > > >
> > > > > > > -   The 3.3V regulator has been getting a bit warmer than I like, so I
> > > > > > >     have been planning to use a buck converter instead. But maybe I
> > > > > > >     should
> > > > > > >
> > >
> > > > > > > run two 3.3V regulators instead? I would think that the buck
> > > > > > > converter
> > >
> > > > > > > would be pass less of the noise through.
> > > > > > >
> > > > > > > -   I ran over there quickly to pick up stuff and tried a crude
> > > > > > >     (uncalculated) common-mode choke I made up from stuff I could find.
> > > > > > >     Did
> > > > > > >
> > >
> > > > > > > not make in dent in the noise coming through.
> > > > > > > See here...
> > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
> > > > > > >
> > > > > > > -   I feel like Brent may be correct, that the noise may be coming from
> > > > > > >     the relay side. The processor (ESP32) is resetting. I know it's
> > > > > > >     not a
> > > > > > >
> > >
> > > > > > > firmware issue as it had zero crashes with the previous pump.
> > > > > > > Adding some info:
> > > > > > > The previous pump was a huge AC pump. This new pump is actually DC,
> > > > > > > but
> > >
> > > > > > > there's a bridge rectifier on the wires. So I'm now convinced that
> > > > > > > the
> > >
> > > > > > > noise is coming from brushes.
> > > > > > > I brought the pump with me, and I have a new blank board. My plan
> > > > > > > is to
> > >
> > > > > > > reproduce just enough of the circuit to see the noise, and I can cut
> > > > > > > and
> > >
> > > > > > > re-route traces (the 5V & ground to the relays) to see if helps.
> > > > > > > I will also add a ceramic capacitor to the pump wires (right at the
> > > > > > > pump), and hope that helps. Plus twist the wires.
> > > > > > > I'll be back with some results.
> > > > > > > Cheers,
> > > > > > > -Neil.
> > > > > > > On 12/10/2020 7:28 PM, FTL wrote:
> > > > > > >
> > > > > > > > This is almost too obvious, but in the schematic I do not see a
> > > > > > > > flyback
> > >
> > > > > > > > diode across the relay to suppress the back EMF when the relay is
> > > > > > > > turned
> > > > > >
> > > > > > > > off. The lack of diode would cause a serious spike in the 5V supply
> > > > > > > > when
> > > > > >
> > > > > > > the
> > > > > > >
> > > > > > > > relay is turned off.
> > > > > > > > Is the transistor being turned on hard enough to keep the relay on
> > > > > > > > properly.
> > > > > > > > If it is not fully on with no flyback diode, maybe it is
> > > > > > > > occasionally
> > >
> > > > > > > > releasing and causing big noise on the 5V bus.
> > > > > > > >
> > > > > > > > > -----Original Message-----
> > > > > > > > > From: [hidden email] [hidden email] On Behalf
> > > > > > > > > Of
> > >
> > > > > > > Neil
> > > > > > >
> > > > > > > > > Sent: December 8, 2020 11:04 AM
> > > > > > > > > To: Microcontroller discussion list - Public. [hidden email]
> > > > > > > > > Subject: [EE] Eliminating external noise through PS
> > > > > > > > > Hi,
> > > > > > > > > I'm working on a device that takes 120VAC, converts to 5VDC with a
> > > > > > > > > PCB-
> > > > > >
> > > > > > > > > mounted power supply, then further reduces that to 3.3VDC with a
> > > > > > > > > linear
> > > > > >
> > > > > > > > > regulator.
> > > > > > > > > A 3.3V microcontroller switches a relay to power a 120VAC pump.
> > > > > > > > > Overview...
> > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
> > > > > > > > > All has been great until we switched to a specific pump, which
> > > > > > > > > happens
> > >
> > > > > > > to
> > > > > > >
> > > > > > > > > generate a LOT of conducted noise, which passes through the 5V PS,
> > > > > > > > > and
> > >
> > > > > > > the
> > > > > > >
> > > > > > > > > 3.3V regulator, and causing the microcontroller to crash.
> > > > > > > > > I did a bunch of tested and found that the noise is being conducted
> > > > > > > > > through
> > > > > > > > > the wires back to the board through the PS, through the linear
> > > > > > > > > regulator,
> > > > > > > > > and
> > > > > > > >
> > > > > > > > > this is the 3.3V line...
> > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
> > > > > > > > > I was over at someone else's place so did not have a lot of parts
> > > > > > > > > with
> > >
> > > > > > > me,
> > > > > > >
> > > > > > > > > but...
> > > > > > > > > Adding a bunch more 0.1uf bypass capacitors all over the board did
> > > > > > > > > not
> > >
> > > > > > > > help.
> > > > > > > >
> > > > > > > > > Changing the power supply from an IRM-10-5 (industrial spec, 200mV
> > > > > > > > > ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
> > > > > > > > > rate
> > > > > >
> > > > > > > > of
> > > > > > > >
> > > > > > > > > the crashing... but the ripple itself wasn't causing crashing.
> > > > > > > > > Adding (non-specific size) ferrites to the pump wires, and 120VAC
> > > > > > > > > input
> > > > > >
> > > > > > > > wires
> > > > > > > >
> > > > > > > > > did not help.
> > > > > > > > > I then tried to create a crude/uncalculated LC filter (which
> > > > > > > > > whatever
> > >
> > > > > > > > > components I had on hand (33uh inductor and 1000uf capacitor,
> > > > > > > > > should
> > >
> > > > > be
> > > > >
> > > > > > > > > low ESR), then a Pi filter (added 680 uF capacitor), and those
> > > > > > > > > barely
> > >
> > > > > > > made
> > > > > > >
> > > > > > > > a
> > > > > > > >
> > > > > > > > > dent.
> > > > > > > > > Eventually I added another 0.1uf capacitor to the output side of
> > > > > > > > > the
> > >
> > > > > pi
> > > > >
> > > > > > > > filter
> > > > > > > >
> > > > > > > > > and that helped enough to prevent the microcontroller crashing.
> > > > > > > > > But there is still a lot of noise on the 3.3V line...
> > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
> > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
> > > > > > > > > FWIW, this is where it ended up...
> > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
> > > > > > > > > The noise is in the 7Mhz to 30Mhz range (prob even higher).
> > > > > > > > > I feel like smaller, low-ESR ceramic caps should help, but I doubt
> > > > > > > > > it
> > >
> > > > > > > will
> > > > > > >
> > > > > > > > take
> > > > > > > >
> > > > > > > > > out most of the noise.
> > > > > > > > > What is the right type of filter to eliminate this noise?
> > > > > > > > > Cheers,
> > > > > > > > > -Neil.
> > > > > > > > > --
> > > > > > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > > > > > > View/change your membership options at
> > > > > > > > > http://mailman.mit.edu/mailman/listinfo/piclist
> > > > > > > > > --
> > > > > > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > > > > > > View/change your membership options at
> > > > > > > > > http://mailman.mit.edu/mailman/listinfo/piclist
> > > > >
> > > > > --
> > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > > View/change your membership options at
> > > > > http://mailman.mit.edu/mailman/listinfo/piclist
> >
> > --
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> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist
>
> --
>
> Jason White
>
> ------------
>
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist



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Re: [EE] Eliminating external noise through PS

madscientistatlarge
In reply to this post by Jason White-20
It occurs to me that the filter, however done should also be at the motor end, to limit transmission through air of the noise signal, i.e. don't give it a big antenna.


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‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Tuesday, December 29, 2020 12:36 PM, Jason White <[hidden email]> wrote:

> My experience developing "all discrete" (no microcontroller) motor driver
> PCBs is that any noise that is unaffected by filtering tends to be a
> measurement or environmental artifact.
>
> I'd recommend doubled checking your probe/scope grounding - it is an
> endless source of trouble and erroneous readings. I've found that often
> times problems in systems are a result of a combination of "innocent
> looking" and unrelated things that end up interacting in unexpected ways.
>
> On Tuesday, December 29, 2020, Neil [hidden email] wrote:
>
> > Happy holidays everyone.
> > Okay, I got back to this recently and have a bunch of updates:
> > For the tl;dr 'ers... I've got a lot of noise out, the processor does
> > not crash anymore, but 2 questions remain:
> >
> > -   Should I have the AC-outlet ground wire, coming onto the PCB and used
> >     as a shield?
> >
> > -   If I hold the AC wire with my hand, the noise (as seen on the
> >     oscilloscope) drops (noticeably). Shielding the AC wire does not have
> >     the same effect, so what is happening here, and how can I use this to
> >     help reduce the noise even more?
> >
> >
> > For the gory details, here's my summary of what I tried and found...
> > For reference...
> > http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
> > noise is mostly in the few Mhz range and higher.
> >
> > -   Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
> > -   Low-pass filter helped minimally
> > -   Pi filter was a bit better, but still small impact.
> > -   Common mode choke (uncalculated, but should've been able to separate
> >     60Hz from Mhz-range noise) didn't help. I am new to these, but
> >     apparently above some frequency the impedance drops again.
> >
> > -   Ferrite across AC side of motor wires helped minimally.
> > -   Ferrite on incoming-power AC wires did not help
> > -   Removed relay (and jumper across contacts to run the pump) to see if
> >     noise was coming into board from that side, but nope.
> >
> > -   Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
> >     with wires soldered on for the incoming power and parallel wires to run
> >     the pump, and a 1k load resistor on the PS output. Still a lot of noise
> >
> > -   Low-pass filter again helped reduce noise minimally.
> > -   Capacitance multiplier helped noticeably.
> > -   2 more ceramic caps from each motor wire to ground/motor case (right
> >     at the motor) helped noticeably.
> >
> > -   Twisted the AC wires to the motor tighter, and didn't really see any
> >     difference.
> >
> > -   Back to original board, to use some of these, but too much voltage
> >     drop on capacitance multiplier to be usable. I should calculate this
> >     properly and find the right transistor for this.
> >
> >
> > At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
> > filter and the board isn't crashing, but I can still see some noise on
> > the scope, which I'd like to reduce even more. Going to try a
> > multi-stage pi/LC filter.
> > But I'm curious how to use the "phenomenon" where holding the AC wire in
> > my hand reduces noise noticeably, to help this.
> > Thanks,
> > -Neil.
> > On 12/13/2020 7:15 PM, Neil wrote:
> >
> > > That's a definite possibility at this point. The original circuit
> > > (prior version) worked great with 2 layers, but I needed 2oz copper to
> > > handle the pump current.
> > > Never version works just as great. Or I should say "worked", until
> > > they decided to switch from the AC pump to this DC pump.
> > > Cheers,
> > > -Neil
> > > On 12/13/2020 6:58 PM, Jason White wrote:
> > >
> > > > Neil, from the pictures it looks like you're using a 2 layer PCB. Have
> > > > you
> > >
> > > > considered a 4 layer PCB? A continuous dedicated ground plane layer
> > > > would
> > >
> > > > drastically reduce the loop area (and thus susceptibility to EMI) of
> > > > your
> > >
> > > > traces.
> > > > Otherwise, it may be worth considering moving the relays to a separate
> > > > board/area.
> > > > On Sunday, December 13, 2020, Neil [hidden email] wrote:
> > > >
> > > > > I strongly feel so, because in my early tests, I:
> > > > > (a) disconnected one of the pump wires (so the pump wouldn't run), and
> > > > > it was (expectedly) very clean (on the scope).
> > > > > (b) disconnected both of the pump wires and plugged it into the female
> > > > > side of a PC power cord, so the pump ran, but was connected to 120VAC
> > > > > from a different source. Very clean power again.
> > > > > In both cases, all else stayed the same including where the wires were
> > > > > draped, etc.
> > > > > In other tests, I moved the scope, power lines, etc and no change to
> > > > > the
> > >
> > > > > noise on the line.
> > > > > Either way, I haven't done my other tests yet since I took the pump
> > > > > with
> > >
> > > > > me, so I'll get to those this week.
> > > > > Cheers,
> > > > > -Neil.
> > > > > On 12/11/2020 7:37 PM, Jason White wrote:
> > > > >
> > > > > > Hi Neil,
> > > > > > This may be a silly question: are you sure that some of these voltage
> > > > > > spikes that you've captured on the scope are not artifacts of your
> > > > > > measurement setup? The loop formed by the ground wire/clip on a scope
> > > > > > probe
> > > > > > makes a very effective antenna. Maybe your power rail is cleaner than
> > > > > > you
> > >
> > > > > > think - in which case the true problem might be elsewhere.
> > > > > > -Jason White
> > > > > > On Fri, Dec 11, 2020 at 3:11 PM Neil [hidden email] wrote:
> > > > > >
> > > > > > > Sorry, disappeared for a couple days, but some quick answers to
> > > > > > > everything for now, and my next steps:
> > > > > > >
> > > > > > > -   Yes I have flyback diodes. Highlighted with yellow here, just
> > > > > > >     above
> > > > > > >
> > >
> > > > > > > the relays...
> > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
> > > > > > >
> > > > > > > -   James & Russell, in that diagram also, I labeled the paths for
> > > > > > >     power.
> > > > > > >
> > >
> > > > > > > The 5V to the relays is pretty much dedicated and 5V is on the top
> > > > > > > layer, and (dedicated) ground for the relays on the bottom layer.
> > > > > > > But
> > >
> > > > > > > yes, it's right up against the AC section, but as many components
> > > > > > > have
> > >
> > > > > > > been removed now, I will push that far away.
> > > > > > >
> > > > > > > -   The 3.3V regulator has been getting a bit warmer than I like, so I
> > > > > > >     have been planning to use a buck converter instead. But maybe I
> > > > > > >     should
> > > > > > >
> > >
> > > > > > > run two 3.3V regulators instead? I would think that the buck
> > > > > > > converter
> > >
> > > > > > > would be pass less of the noise through.
> > > > > > >
> > > > > > > -   I ran over there quickly to pick up stuff and tried a crude
> > > > > > >     (uncalculated) common-mode choke I made up from stuff I could find.
> > > > > > >     Did
> > > > > > >
> > >
> > > > > > > not make in dent in the noise coming through.
> > > > > > > See here...
> > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
> > > > > > >
> > > > > > > -   I feel like Brent may be correct, that the noise may be coming from
> > > > > > >     the relay side. The processor (ESP32) is resetting. I know it's
> > > > > > >     not a
> > > > > > >
> > >
> > > > > > > firmware issue as it had zero crashes with the previous pump.
> > > > > > > Adding some info:
> > > > > > > The previous pump was a huge AC pump. This new pump is actually DC,
> > > > > > > but
> > >
> > > > > > > there's a bridge rectifier on the wires. So I'm now convinced that
> > > > > > > the
> > >
> > > > > > > noise is coming from brushes.
> > > > > > > I brought the pump with me, and I have a new blank board. My plan
> > > > > > > is to
> > >
> > > > > > > reproduce just enough of the circuit to see the noise, and I can cut
> > > > > > > and
> > >
> > > > > > > re-route traces (the 5V & ground to the relays) to see if helps.
> > > > > > > I will also add a ceramic capacitor to the pump wires (right at the
> > > > > > > pump), and hope that helps. Plus twist the wires.
> > > > > > > I'll be back with some results.
> > > > > > > Cheers,
> > > > > > > -Neil.
> > > > > > > On 12/10/2020 7:28 PM, FTL wrote:
> > > > > > >
> > > > > > > > This is almost too obvious, but in the schematic I do not see a
> > > > > > > > flyback
> > >
> > > > > > > > diode across the relay to suppress the back EMF when the relay is
> > > > > > > > turned
> > > > > >
> > > > > > > > off. The lack of diode would cause a serious spike in the 5V supply
> > > > > > > > when
> > > > > >
> > > > > > > the
> > > > > > >
> > > > > > > > relay is turned off.
> > > > > > > > Is the transistor being turned on hard enough to keep the relay on
> > > > > > > > properly.
> > > > > > > > If it is not fully on with no flyback diode, maybe it is
> > > > > > > > occasionally
> > >
> > > > > > > > releasing and causing big noise on the 5V bus.
> > > > > > > >
> > > > > > > > > -----Original Message-----
> > > > > > > > > From: [hidden email] [hidden email] On Behalf
> > > > > > > > > Of
> > >
> > > > > > > Neil
> > > > > > >
> > > > > > > > > Sent: December 8, 2020 11:04 AM
> > > > > > > > > To: Microcontroller discussion list - Public. [hidden email]
> > > > > > > > > Subject: [EE] Eliminating external noise through PS
> > > > > > > > > Hi,
> > > > > > > > > I'm working on a device that takes 120VAC, converts to 5VDC with a
> > > > > > > > > PCB-
> > > > > >
> > > > > > > > > mounted power supply, then further reduces that to 3.3VDC with a
> > > > > > > > > linear
> > > > > >
> > > > > > > > > regulator.
> > > > > > > > > A 3.3V microcontroller switches a relay to power a 120VAC pump.
> > > > > > > > > Overview...
> > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
> > > > > > > > > All has been great until we switched to a specific pump, which
> > > > > > > > > happens
> > >
> > > > > > > to
> > > > > > >
> > > > > > > > > generate a LOT of conducted noise, which passes through the 5V PS,
> > > > > > > > > and
> > >
> > > > > > > the
> > > > > > >
> > > > > > > > > 3.3V regulator, and causing the microcontroller to crash.
> > > > > > > > > I did a bunch of tested and found that the noise is being conducted
> > > > > > > > > through
> > > > > > > > > the wires back to the board through the PS, through the linear
> > > > > > > > > regulator,
> > > > > > > > > and
> > > > > > > >
> > > > > > > > > this is the 3.3V line...
> > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
> > > > > > > > > I was over at someone else's place so did not have a lot of parts
> > > > > > > > > with
> > >
> > > > > > > me,
> > > > > > >
> > > > > > > > > but...
> > > > > > > > > Adding a bunch more 0.1uf bypass capacitors all over the board did
> > > > > > > > > not
> > >
> > > > > > > > help.
> > > > > > > >
> > > > > > > > > Changing the power supply from an IRM-10-5 (industrial spec, 200mV
> > > > > > > > > ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
> > > > > > > > > rate
> > > > > >
> > > > > > > > of
> > > > > > > >
> > > > > > > > > the crashing... but the ripple itself wasn't causing crashing.
> > > > > > > > > Adding (non-specific size) ferrites to the pump wires, and 120VAC
> > > > > > > > > input
> > > > > >
> > > > > > > > wires
> > > > > > > >
> > > > > > > > > did not help.
> > > > > > > > > I then tried to create a crude/uncalculated LC filter (which
> > > > > > > > > whatever
> > >
> > > > > > > > > components I had on hand (33uh inductor and 1000uf capacitor,
> > > > > > > > > should
> > >
> > > > > be
> > > > >
> > > > > > > > > low ESR), then a Pi filter (added 680 uF capacitor), and those
> > > > > > > > > barely
> > >
> > > > > > > made
> > > > > > >
> > > > > > > > a
> > > > > > > >
> > > > > > > > > dent.
> > > > > > > > > Eventually I added another 0.1uf capacitor to the output side of
> > > > > > > > > the
> > >
> > > > > pi
> > > > >
> > > > > > > > filter
> > > > > > > >
> > > > > > > > > and that helped enough to prevent the microcontroller crashing.
> > > > > > > > > But there is still a lot of noise on the 3.3V line...
> > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
> > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
> > > > > > > > > FWIW, this is where it ended up...
> > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
> > > > > > > > > The noise is in the 7Mhz to 30Mhz range (prob even higher).
> > > > > > > > > I feel like smaller, low-ESR ceramic caps should help, but I doubt
> > > > > > > > > it
> > >
> > > > > > > will
> > > > > > >
> > > > > > > > take
> > > > > > > >
> > > > > > > > > out most of the noise.
> > > > > > > > > What is the right type of filter to eliminate this noise?
> > > > > > > > > Cheers,
> > > > > > > > > -Neil.
> > > > > > > > > --
> > > > > > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > > > > > > View/change your membership options at
> > > > > > > > > http://mailman.mit.edu/mailman/listinfo/piclist
> > > > > > > > > --
> > > > > > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > > > > > > View/change your membership options at
> > > > > > > > > http://mailman.mit.edu/mailman/listinfo/piclist
> > > > >
> > > > > --
> > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > > View/change your membership options at
> > > > > http://mailman.mit.edu/mailman/listinfo/piclist
> >
> > --
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> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist
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> --
>
> Jason White
>
> ------------
>
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> View/change your membership options at
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Re: [EE] Eliminating external noise through PS

Alan Pearce
In reply to this post by madscientistatlarge
On Tue, 29 Dec 2020 20:34:20 +0000
madscientistatlarge <[hidden email]> wrote:

> When you measure with the scope, how are you grounding the Probe?
> Those convenient wires with alligator clips make good antennas, best
> to take a wire, preferably beryllium copper because it's springy, and
> wrap one end around the exposed ground just behind the tip, then bend
> it to point the same way as the signal probe and trim to length so
> you are grounding it right where you are measuring.

Reminds me of a work colleague about 30 years ago, who was attempting
to fault find a bit slice CPU. He had about 2 feet of hookup wire from
the ground terminal on the front of the scope to an easily accessible
grounding point which I don't remember the location of, but it could
have been on the backplane. he then wondered why he couldn't see any
signals in the circuit under investigation except a mighty large mains
frequency sine wave at seemingly much higher amplitude than the the TTL
signal he was trying to measure. He seemed a bit put out that it didn't
do what he wanted.
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Re: [EE] Eliminating external noise through PS

David VanHorn-2
In reply to this post by Neil
What's your reset circuit look like?   High enough impedances here can
cause these problems.

On Tue, Dec 29, 2020, 11:22 AM Neil <[hidden email]> wrote:

> Happy holidays everyone.
>
> Okay, I got back to this recently and have a bunch of updates:
>
> For the tl;dr 'ers... I've got a lot of noise out, the processor does
> not crash anymore, but 2 questions remain:
>
> - Should I have the AC-outlet ground wire, coming onto the PCB and used
> as a shield?
>
> - If I hold the AC wire with my hand, the noise (as seen on the
> oscilloscope) drops (noticeably).  Shielding the AC wire does not have
> the same effect, so what is happening here, and how can I use this to
> help reduce the noise even more?
>
>
> For the gory details, here's my summary of what I tried and found...
>
> For reference...
> http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
> noise is mostly in the few Mhz range and higher.
>
> - Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
> - Low-pass filter helped minimally
> - Pi filter was a bit better, but still small impact.
> - Common mode choke (uncalculated, but should've been able to separate
> 60Hz from Mhz-range noise) didn't help.  I am new to these, but
> apparently above some frequency the impedance drops again.
> - Ferrite across AC side of motor wires helped minimally.
> - Ferrite on incoming-power AC wires did not help
> - Removed relay (and jumper across contacts to run the pump) to see if
> noise was coming into board from that side, but nope.
> - Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
> with wires soldered on for the incoming power and parallel wires to run
> the pump, and a 1k load resistor on the PS output. Still a lot of noise
> - Low-pass filter again helped reduce noise minimally.
> - Capacitance multiplier helped noticeably.
> - 2 more ceramic caps from each motor wire to ground/motor case (right
> at the motor) helped noticeably.
> - Twisted the AC wires to the motor tighter, and didn't really see any
> difference.
> - Back to original board, to use some of these, but too much voltage
> drop on capacitance multiplier to be usable.  I should calculate this
> properly and find the right transistor for this.
>
> At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
> filter and the board isn't crashing, but I can still see some noise on
> the scope, which I'd like to reduce even more.  Going to try a
> multi-stage pi/LC filter.
>
> But I'm curious how to use the "phenomenon" where holding the AC wire in
> my hand reduces noise noticeably, to help this.
>
>
> Thanks,
> -Neil.
>
>
>
> On 12/13/2020 7:15 PM, Neil wrote:
> > That's a definite possibility at this point.  The original circuit
> > (prior version) worked great with 2 layers, but I needed 2oz copper to
> > handle the pump current.
> > Never version works just as great.  Or  I should say "worked", until
> > they decided to switch from the AC pump to this DC pump.
> >
> > Cheers,
> > -Neil
> >
> >
> >
> > On 12/13/2020 6:58 PM, Jason White wrote:
> >> Neil, from the pictures it looks like you're using a 2 layer PCB. Have
> you
> >> considered a 4 layer PCB? A continuous dedicated ground plane layer
> would
> >> drastically reduce the loop area (and thus susceptibility to EMI) of
> your
> >> traces.
> >>
> >> Otherwise, it may be worth considering moving the relays to a separate
> >> board/area.
> >>
> >> On Sunday, December 13, 2020, Neil <[hidden email]> wrote:
> >>
> >>> I strongly feel so, because in my early tests, I:
> >>> (a) disconnected one of the pump wires (so the pump wouldn't run), and
> >>> it was (expectedly) very clean (on the scope).
> >>> (b) disconnected both of the pump wires and plugged it into the female
> >>> side of a PC power cord, so the pump ran, but was connected to 120VAC
> >>> from a different source.  Very clean power again.
> >>> In both cases, all else stayed the same including where the wires were
> >>> draped, etc.
> >>>
> >>> In other tests, I moved the scope, power lines, etc and no change to
> the
> >>> noise on the line.
> >>>
> >>> Either way, I haven't done my other tests yet since I took the pump
> with
> >>> me, so I'll get to those this week.
> >>>
> >>> Cheers,
> >>> -Neil.
> >>>
> >>>
> >>> On 12/11/2020 7:37 PM, Jason White wrote:
> >>>> Hi Neil,
> >>>>
> >>>> This may be a silly question: are you sure that some of these voltage
> >>>> spikes that you've captured on the scope are not artifacts of your
> >>>> measurement setup? The loop formed by the ground wire/clip on a scope
> >>> probe
> >>>> makes a very effective antenna. Maybe your power rail is cleaner than
> you
> >>>> think - in which case the true problem might be elsewhere.
> >>>>
> >>>> -Jason White
> >>>>
> >>>> On Fri, Dec 11, 2020 at 3:11 PM Neil <[hidden email]> wrote:
> >>>>
> >>>>> Sorry, disappeared for a couple days, but some quick answers to
> >>>>> everything for now, and my next steps:
> >>>>>
> >>>>> - Yes I have flyback diodes.   Highlighted with yellow here,  just
> above
> >>>>> the relays...
> >>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
> >>>>> - James & Russell, in that diagram also, I labeled the paths for
> power.
> >>>>> The 5V to the relays is pretty much dedicated and 5V is on the top
> >>>>> layer, and (dedicated) ground for the relays on the bottom layer.
> But
> >>>>> yes, it's right up against the AC section, but as many components
> have
> >>>>> been removed now, I will push that far away.
> >>>>> - The 3.3V regulator has been getting a bit warmer than I like, so I
> >>>>> have been planning to use a buck converter instead.  But maybe I
> should
> >>>>> run two 3.3V regulators instead?  I would think that the buck
> converter
> >>>>> would be pass less of the noise through.
> >>>>> - I ran over there quickly to pick up stuff and tried a crude
> >>>>> (uncalculated) common-mode choke I made up from stuff I could find.
> Did
> >>>>> not make in dent in the noise coming through.
> >>>>> See here...
> >>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
> >>>>> - I feel like Brent may be correct, that the noise may be coming from
> >>>>> the relay side.  The processor (ESP32) is resetting.  I know it's
> not a
> >>>>> firmware issue as it had zero crashes with the previous pump.
> >>>>>
> >>>>>
> >>>>> Adding some info:
> >>>>> The previous pump was a huge AC pump.  This new pump is actually DC,
> but
> >>>>> there's a bridge rectifier on the wires.  So I'm now convinced that
> the
> >>>>> noise is coming from brushes.
> >>>>> I brought the pump with me, and I have a new blank board.  My plan
> is to
> >>>>> reproduce just enough of the circuit to see the noise, and I can cut
> and
> >>>>> re-route traces (the 5V & ground to the relays) to see if helps.
> >>>>> I will also add a ceramic capacitor to the pump wires (right at the
> >>>>> pump), and hope that helps.  Plus twist the wires.
> >>>>>
> >>>>> I'll be back with some results.
> >>>>>
> >>>>> Cheers,
> >>>>> -Neil.
> >>>>>
> >>>>>
> >>>>>
> >>>>> On 12/10/2020 7:28 PM, FTL wrote:
> >>>>>> This is almost too obvious, but in the schematic I do not see a
> flyback
> >>>>>> diode across the relay to suppress the back EMF when the relay is
> >>> turned
> >>>>>> off. The lack of diode would cause a serious spike in the 5V supply
> >>> when
> >>>>> the
> >>>>>> relay is turned off.
> >>>>>>
> >>>>>> Is the transistor being turned on hard enough to keep the relay on
> >>>>> properly.
> >>>>>> If it is not fully on with no flyback diode, maybe it is
> occasionally
> >>>>>> releasing and causing big noise on the 5V bus.
> >>>>>>
> >>>>>>> -----Original Message-----
> >>>>>>> From: [hidden email] <[hidden email]> On Behalf
> Of
> >>>>> Neil
> >>>>>>> Sent: December 8, 2020 11:04 AM
> >>>>>>> To: Microcontroller discussion list - Public. <[hidden email]>
> >>>>>>> Subject: [EE] Eliminating external noise through PS
> >>>>>>>
> >>>>>>> Hi,
> >>>>>>>
> >>>>>>> I'm working on a device that takes 120VAC, converts to 5VDC with a
> >>> PCB-
> >>>>>>> mounted power supply, then further reduces that to 3.3VDC with a
> >>> linear
> >>>>>>> regulator.
> >>>>>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
> >>>>>>> Overview...
> >>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
> >>>>>>>
> >>>>>>> All has been great until we switched to a specific pump, which
> happens
> >>>>> to
> >>>>>>> generate a LOT of conducted noise, which passes through the 5V PS,
> and
> >>>>> the
> >>>>>>> 3.3V regulator, and causing the microcontroller to crash.
> >>>>>>> I did a bunch of tested and found that the noise is being conducted
> >>>>>> through
> >>>>>>> the wires back to the board through the PS, through the linear
> >>>>> regulator,
> >>>>>> and
> >>>>>>> this is the 3.3V line...
> >>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
> >>>>>>>
> >>>>>>> I was over at someone else's place so did not have a lot of parts
> with
> >>>>> me,
> >>>>>>> but...
> >>>>>>> Adding a bunch more 0.1uf bypass capacitors all over the board did
> not
> >>>>>> help.
> >>>>>>> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
> >>>>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
> >>> rate
> >>>>>> of
> >>>>>>> the crashing... but the ripple itself wasn't causing crashing.
> >>>>>>>
> >>>>>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC
> >>> input
> >>>>>> wires
> >>>>>>> did not help.
> >>>>>>> I then tried to create a crude/uncalculated LC filter (which
> whatever
> >>>>>>> components I had on hand (33uh inductor and 1000uf capacitor,
> should
> >>> be
> >>>>>>> low ESR), then a Pi filter (added 680 uF capacitor), and those
> barely
> >>>>> made
> >>>>>> a
> >>>>>>> dent.
> >>>>>>> Eventually I added another 0.1uf capacitor to the output side of
> the
> >>> pi
> >>>>>> filter
> >>>>>>> and that helped enough to prevent the microcontroller crashing.
> >>>>>>> But there is still a lot of noise on the 3.3V line...
> >>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
> >>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
> >>>>>>>
> >>>>>>> FWIW, this is where it ended up...
> >>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
> >>>>>>>
> >>>>>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
> >>>>>>> I feel like smaller, low-ESR ceramic caps should help, but I doubt
> it
> >>>>> will
> >>>>>> take
> >>>>>>> out most of the noise.
> >>>>>>> What is the right type of filter to eliminate this noise?
> >>>>>>>
> >>>>>>> Cheers,
> >>>>>>> -Neil.
> >>>>>>>
> >>>>>>> --
> >>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> >>>>>>> View/change your membership options at
> >>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
> >>>>> --
> >>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> >>>>> View/change your membership options at
> >>>>> http://mailman.mit.edu/mailman/listinfo/piclist
> >>>>>
> >>> --
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> >>> View/change your membership options at
> >>> http://mailman.mit.edu/mailman/listinfo/piclist
> >>>
>
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Re: [EE] Eliminating external noise through PS

Bob Blick-5
In reply to this post by Neil
Hi Neil,

I've found that measuring current is quite often better than measuring voltage when seeking out noise problems. I can be less convenient to do but at least where wires enter and exit the board it can be quite useful. Do you have a current clamp you can attach to your scope?

Cheerful regards, Bob

________________________________________
From: [hidden email] <[hidden email]> on behalf of Neil
Sent: Tuesday, December 29, 2020 10:20 AM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Eliminating external noise through PS

Happy holidays everyone.

Okay, I got back to this recently and have a bunch of updates:

For the tl;dr 'ers... I've got a lot of noise out, the processor does
not crash anymore, but 2 questions remain:

- Should I have the AC-outlet ground wire, coming onto the PCB and used
as a shield?

- If I hold the AC wire with my hand, the noise (as seen on the
oscilloscope) drops (noticeably).  Shielding the AC wire does not have
the same effect, so what is happening here, and how can I use this to
help reduce the noise even more?


For the gory details, here's my summary of what I tried and found...

For reference...
http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
noise is mostly in the few Mhz range and higher.

- Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
- Low-pass filter helped minimally
- Pi filter was a bit better, but still small impact.
- Common mode choke (uncalculated, but should've been able to separate
60Hz from Mhz-range noise) didn't help.  I am new to these, but
apparently above some frequency the impedance drops again.
- Ferrite across AC side of motor wires helped minimally.
- Ferrite on incoming-power AC wires did not help
- Removed relay (and jumper across contacts to run the pump) to see if
noise was coming into board from that side, but nope.
- Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
with wires soldered on for the incoming power and parallel wires to run
the pump, and a 1k load resistor on the PS output. Still a lot of noise
- Low-pass filter again helped reduce noise minimally.
- Capacitance multiplier helped noticeably.
- 2 more ceramic caps from each motor wire to ground/motor case (right
at the motor) helped noticeably.
- Twisted the AC wires to the motor tighter, and didn't really see any
difference.
- Back to original board, to use some of these, but too much voltage
drop on capacitance multiplier to be usable.  I should calculate this
properly and find the right transistor for this.

At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
filter and the board isn't crashing, but I can still see some noise on
the scope, which I'd like to reduce even more.  Going to try a
multi-stage pi/LC filter.

But I'm curious how to use the "phenomenon" where holding the AC wire in
my hand reduces noise noticeably, to help this.


Thanks,
-Neil.



On 12/13/2020 7:15 PM, Neil wrote:

> That's a definite possibility at this point.  The original circuit
> (prior version) worked great with 2 layers, but I needed 2oz copper to
> handle the pump current.
> Never version works just as great.  Or  I should say "worked", until
> they decided to switch from the AC pump to this DC pump.
>
> Cheers,
> -Neil
>
>
>
> On 12/13/2020 6:58 PM, Jason White wrote:
>> Neil, from the pictures it looks like you're using a 2 layer PCB. Have you
>> considered a 4 layer PCB? A continuous dedicated ground plane layer would
>> drastically reduce the loop area (and thus susceptibility to EMI) of your
>> traces.
>>
>> Otherwise, it may be worth considering moving the relays to a separate
>> board/area.
>>
>> On Sunday, December 13, 2020, Neil <[hidden email]> wrote:
>>
>>> I strongly feel so, because in my early tests, I:
>>> (a) disconnected one of the pump wires (so the pump wouldn't run), and
>>> it was (expectedly) very clean (on the scope).
>>> (b) disconnected both of the pump wires and plugged it into the female
>>> side of a PC power cord, so the pump ran, but was connected to 120VAC
>>> from a different source.  Very clean power again.
>>> In both cases, all else stayed the same including where the wires were
>>> draped, etc.
>>>
>>> In other tests, I moved the scope, power lines, etc and no change to the
>>> noise on the line.
>>>
>>> Either way, I haven't done my other tests yet since I took the pump with
>>> me, so I'll get to those this week.
>>>
>>> Cheers,
>>> -Neil.
>>>
>>>
>>> On 12/11/2020 7:37 PM, Jason White wrote:
>>>> Hi Neil,
>>>>
>>>> This may be a silly question: are you sure that some of these voltage
>>>> spikes that you've captured on the scope are not artifacts of your
>>>> measurement setup? The loop formed by the ground wire/clip on a scope
>>> probe
>>>> makes a very effective antenna. Maybe your power rail is cleaner than you
>>>> think - in which case the true problem might be elsewhere.
>>>>
>>>> -Jason White
>>>>
>>>> On Fri, Dec 11, 2020 at 3:11 PM Neil <[hidden email]> wrote:
>>>>
>>>>> Sorry, disappeared for a couple days, but some quick answers to
>>>>> everything for now, and my next steps:
>>>>>
>>>>> - Yes I have flyback diodes.   Highlighted with yellow here,  just above
>>>>> the relays...
>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
>>>>> - James & Russell, in that diagram also, I labeled the paths for power.
>>>>> The 5V to the relays is pretty much dedicated and 5V is on the top
>>>>> layer, and (dedicated) ground for the relays on the bottom layer.  But
>>>>> yes, it's right up against the AC section, but as many components have
>>>>> been removed now, I will push that far away.
>>>>> - The 3.3V regulator has been getting a bit warmer than I like, so I
>>>>> have been planning to use a buck converter instead.  But maybe I should
>>>>> run two 3.3V regulators instead?  I would think that the buck converter
>>>>> would be pass less of the noise through.
>>>>> - I ran over there quickly to pick up stuff and tried a crude
>>>>> (uncalculated) common-mode choke I made up from stuff I could find. Did
>>>>> not make in dent in the noise coming through.
>>>>> See here...
>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
>>>>> - I feel like Brent may be correct, that the noise may be coming from
>>>>> the relay side.  The processor (ESP32) is resetting.  I know it's not a
>>>>> firmware issue as it had zero crashes with the previous pump.
>>>>>
>>>>>
>>>>> Adding some info:
>>>>> The previous pump was a huge AC pump.  This new pump is actually DC, but
>>>>> there's a bridge rectifier on the wires.  So I'm now convinced that the
>>>>> noise is coming from brushes.
>>>>> I brought the pump with me, and I have a new blank board.  My plan is to
>>>>> reproduce just enough of the circuit to see the noise, and I can cut and
>>>>> re-route traces (the 5V & ground to the relays) to see if helps.
>>>>> I will also add a ceramic capacitor to the pump wires (right at the
>>>>> pump), and hope that helps.  Plus twist the wires.
>>>>>
>>>>> I'll be back with some results.
>>>>>
>>>>> Cheers,
>>>>> -Neil.
>>>>>
>>>>>
>>>>>
>>>>> On 12/10/2020 7:28 PM, FTL wrote:
>>>>>> This is almost too obvious, but in the schematic I do not see a flyback
>>>>>> diode across the relay to suppress the back EMF when the relay is
>>> turned
>>>>>> off. The lack of diode would cause a serious spike in the 5V supply
>>> when
>>>>> the
>>>>>> relay is turned off.
>>>>>>
>>>>>> Is the transistor being turned on hard enough to keep the relay on
>>>>> properly.
>>>>>> If it is not fully on with no flyback diode, maybe it is occasionally
>>>>>> releasing and causing big noise on the 5V bus.
>>>>>>
>>>>>>> -----Original Message-----
>>>>>>> From: [hidden email] <[hidden email]> On Behalf Of
>>>>> Neil
>>>>>>> Sent: December 8, 2020 11:04 AM
>>>>>>> To: Microcontroller discussion list - Public. <[hidden email]>
>>>>>>> Subject: [EE] Eliminating external noise through PS
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> I'm working on a device that takes 120VAC, converts to 5VDC with a
>>> PCB-
>>>>>>> mounted power supply, then further reduces that to 3.3VDC with a
>>> linear
>>>>>>> regulator.
>>>>>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
>>>>>>> Overview...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
>>>>>>>
>>>>>>> All has been great until we switched to a specific pump, which happens
>>>>> to
>>>>>>> generate a LOT of conducted noise, which passes through the 5V PS, and
>>>>> the
>>>>>>> 3.3V regulator, and causing the microcontroller to crash.
>>>>>>> I did a bunch of tested and found that the noise is being conducted
>>>>>> through
>>>>>>> the wires back to the board through the PS, through the linear
>>>>> regulator,
>>>>>> and
>>>>>>> this is the 3.3V line...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
>>>>>>>
>>>>>>> I was over at someone else's place so did not have a lot of parts with
>>>>> me,
>>>>>>> but...
>>>>>>> Adding a bunch more 0.1uf bypass capacitors all over the board did not
>>>>>> help.
>>>>>>> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
>>>>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
>>> rate
>>>>>> of
>>>>>>> the crashing... but the ripple itself wasn't causing crashing.
>>>>>>>
>>>>>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC
>>> input
>>>>>> wires
>>>>>>> did not help.
>>>>>>> I then tried to create a crude/uncalculated LC filter (which whatever
>>>>>>> components I had on hand (33uh inductor and 1000uf capacitor, should
>>> be
>>>>>>> low ESR), then a Pi filter (added 680 uF capacitor), and those barely
>>>>> made
>>>>>> a
>>>>>>> dent.
>>>>>>> Eventually I added another 0.1uf capacitor to the output side of the
>>> pi
>>>>>> filter
>>>>>>> and that helped enough to prevent the microcontroller crashing.
>>>>>>> But there is still a lot of noise on the 3.3V line...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
>>>>>>>
>>>>>>> FWIW, this is where it ended up...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
>>>>>>>
>>>>>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
>>>>>>> I feel like smaller, low-ESR ceramic caps should help, but I doubt it
>>>>> will
>>>>>> take
>>>>>>> out most of the noise.
>>>>>>> What is the right type of filter to eliminate this noise?
>>>>>>>
>>>>>>> Cheers,
>>>>>>> -Neil.

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Re: [EE] Eliminating external noise through PS

Neil
In reply to this post by Jason White-20
I had previously tried the paperclip-ground mod for the scope probe (saw
this from one of Alan Wolke's videos a long time ago) and it didn't make
much difference.  I should really try this now, after all the changes.

Cheers,
-Neil.





On 12/29/2020 2:36 PM, Jason White wrote:

> My experience developing "all discrete" (no microcontroller) motor driver
> PCBs is that any noise that is unaffected by filtering tends to be a
> measurement or environmental artifact.
>
> I'd recommend doubled checking your probe/scope grounding - it is an
> endless source of trouble and erroneous readings. I've found that often
> times problems in systems are a result of a combination of "innocent
> looking" and unrelated things that end up interacting in unexpected ways.
>
> On Tuesday, December 29, 2020, Neil <[hidden email]> wrote:
>
>> Happy holidays everyone.
>>
>> Okay, I got back to this recently and have a bunch of updates:
>>
>> For the tl;dr 'ers... I've got a lot of noise out, the processor does
>> not crash anymore, but 2 questions remain:
>>
>> - Should I have the AC-outlet ground wire, coming onto the PCB and used
>> as a shield?
>>
>> - If I hold the AC wire with my hand, the noise (as seen on the
>> oscilloscope) drops (noticeably).  Shielding the AC wire does not have
>> the same effect, so what is happening here, and how can I use this to
>> help reduce the noise even more?
>>
>>
>> For the gory details, here's my summary of what I tried and found...
>>
>> For reference...
>> http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
>> noise is mostly in the few Mhz range and higher.
>>
>> - Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
>> - Low-pass filter helped minimally
>> - Pi filter was a bit better, but still small impact.
>> - Common mode choke (uncalculated, but should've been able to separate
>> 60Hz from Mhz-range noise) didn't help.  I am new to these, but
>> apparently above some frequency the impedance drops again.
>> - Ferrite across AC side of motor wires helped minimally.
>> - Ferrite on incoming-power AC wires did not help
>> - Removed relay (and jumper across contacts to run the pump) to see if
>> noise was coming into board from that side, but nope.
>> - Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
>> with wires soldered on for the incoming power and parallel wires to run
>> the pump, and a 1k load resistor on the PS output. Still a lot of noise
>> - Low-pass filter again helped reduce noise minimally.
>> - Capacitance multiplier helped noticeably.
>> - 2 more ceramic caps from each motor wire to ground/motor case (right
>> at the motor) helped noticeably.
>> - Twisted the AC wires to the motor tighter, and didn't really see any
>> difference.
>> - Back to original board, to use some of these, but too much voltage
>> drop on capacitance multiplier to be usable.  I should calculate this
>> properly and find the right transistor for this.
>>
>> At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
>> filter and the board isn't crashing, but I can still see some noise on
>> the scope, which I'd like to reduce even more.  Going to try a
>> multi-stage pi/LC filter.
>>
>> But I'm curious how to use the "phenomenon" where holding the AC wire in
>> my hand reduces noise noticeably, to help this.
>>
>>
>> Thanks,
>> -Neil.
>>
>>
>>
>> On 12/13/2020 7:15 PM, Neil wrote:
>>> That's a definite possibility at this point.  The original circuit
>>> (prior version) worked great with 2 layers, but I needed 2oz copper to
>>> handle the pump current.
>>> Never version works just as great.  Or  I should say "worked", until
>>> they decided to switch from the AC pump to this DC pump.
>>>
>>> Cheers,
>>> -Neil
>>>
>>>
>>>
>>> On 12/13/2020 6:58 PM, Jason White wrote:
>>>> Neil, from the pictures it looks like you're using a 2 layer PCB. Have
>> you
>>>> considered a 4 layer PCB? A continuous dedicated ground plane layer
>> would
>>>> drastically reduce the loop area (and thus susceptibility to EMI) of
>> your
>>>> traces.
>>>>
>>>> Otherwise, it may be worth considering moving the relays to a separate
>>>> board/area.
>>>>
>>>> On Sunday, December 13, 2020, Neil <[hidden email]> wrote:
>>>>
>>>>> I strongly feel so, because in my early tests, I:
>>>>> (a) disconnected one of the pump wires (so the pump wouldn't run), and
>>>>> it was (expectedly) very clean (on the scope).
>>>>> (b) disconnected both of the pump wires and plugged it into the female
>>>>> side of a PC power cord, so the pump ran, but was connected to 120VAC
>>>>> from a different source.  Very clean power again.
>>>>> In both cases, all else stayed the same including where the wires were
>>>>> draped, etc.
>>>>>
>>>>> In other tests, I moved the scope, power lines, etc and no change to
>> the
>>>>> noise on the line.
>>>>>
>>>>> Either way, I haven't done my other tests yet since I took the pump
>> with
>>>>> me, so I'll get to those this week.
>>>>>
>>>>> Cheers,
>>>>> -Neil.
>>>>>
>>>>>
>>>>> On 12/11/2020 7:37 PM, Jason White wrote:
>>>>>> Hi Neil,
>>>>>>
>>>>>> This may be a silly question: are you sure that some of these voltage
>>>>>> spikes that you've captured on the scope are not artifacts of your
>>>>>> measurement setup? The loop formed by the ground wire/clip on a scope
>>>>> probe
>>>>>> makes a very effective antenna. Maybe your power rail is cleaner than
>> you
>>>>>> think - in which case the true problem might be elsewhere.
>>>>>>
>>>>>> -Jason White
>>>>>>
>>>>>> On Fri, Dec 11, 2020 at 3:11 PM Neil <[hidden email]> wrote:
>>>>>>
>>>>>>> Sorry, disappeared for a couple days, but some quick answers to
>>>>>>> everything for now, and my next steps:
>>>>>>>
>>>>>>> - Yes I have flyback diodes.   Highlighted with yellow here,  just
>> above
>>>>>>> the relays...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
>>>>>>> - James & Russell, in that diagram also, I labeled the paths for
>> power.
>>>>>>> The 5V to the relays is pretty much dedicated and 5V is on the top
>>>>>>> layer, and (dedicated) ground for the relays on the bottom layer.
>> But
>>>>>>> yes, it's right up against the AC section, but as many components
>> have
>>>>>>> been removed now, I will push that far away.
>>>>>>> - The 3.3V regulator has been getting a bit warmer than I like, so I
>>>>>>> have been planning to use a buck converter instead.  But maybe I
>> should
>>>>>>> run two 3.3V regulators instead?  I would think that the buck
>> converter
>>>>>>> would be pass less of the noise through.
>>>>>>> - I ran over there quickly to pick up stuff and tried a crude
>>>>>>> (uncalculated) common-mode choke I made up from stuff I could find.
>> Did
>>>>>>> not make in dent in the noise coming through.
>>>>>>> See here...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
>>>>>>> - I feel like Brent may be correct, that the noise may be coming from
>>>>>>> the relay side.  The processor (ESP32) is resetting.  I know it's
>> not a
>>>>>>> firmware issue as it had zero crashes with the previous pump.
>>>>>>>
>>>>>>>
>>>>>>> Adding some info:
>>>>>>> The previous pump was a huge AC pump.  This new pump is actually DC,
>> but
>>>>>>> there's a bridge rectifier on the wires.  So I'm now convinced that
>> the
>>>>>>> noise is coming from brushes.
>>>>>>> I brought the pump with me, and I have a new blank board.  My plan
>> is to
>>>>>>> reproduce just enough of the circuit to see the noise, and I can cut
>> and
>>>>>>> re-route traces (the 5V & ground to the relays) to see if helps.
>>>>>>> I will also add a ceramic capacitor to the pump wires (right at the
>>>>>>> pump), and hope that helps.  Plus twist the wires.
>>>>>>>
>>>>>>> I'll be back with some results.
>>>>>>>
>>>>>>> Cheers,
>>>>>>> -Neil.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 12/10/2020 7:28 PM, FTL wrote:
>>>>>>>> This is almost too obvious, but in the schematic I do not see a
>> flyback
>>>>>>>> diode across the relay to suppress the back EMF when the relay is
>>>>> turned
>>>>>>>> off. The lack of diode would cause a serious spike in the 5V supply
>>>>> when
>>>>>>> the
>>>>>>>> relay is turned off.
>>>>>>>>
>>>>>>>> Is the transistor being turned on hard enough to keep the relay on
>>>>>>> properly.
>>>>>>>> If it is not fully on with no flyback diode, maybe it is
>> occasionally
>>>>>>>> releasing and causing big noise on the 5V bus.
>>>>>>>>
>>>>>>>>> -----Original Message-----
>>>>>>>>> From: [hidden email] <[hidden email]> On Behalf
>> Of
>>>>>>> Neil
>>>>>>>>> Sent: December 8, 2020 11:04 AM
>>>>>>>>> To: Microcontroller discussion list - Public. <[hidden email]>
>>>>>>>>> Subject: [EE] Eliminating external noise through PS
>>>>>>>>>
>>>>>>>>> Hi,
>>>>>>>>>
>>>>>>>>> I'm working on a device that takes 120VAC, converts to 5VDC with a
>>>>> PCB-
>>>>>>>>> mounted power supply, then further reduces that to 3.3VDC with a
>>>>> linear
>>>>>>>>> regulator.
>>>>>>>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
>>>>>>>>> Overview...
>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
>>>>>>>>>
>>>>>>>>> All has been great until we switched to a specific pump, which
>> happens
>>>>>>> to
>>>>>>>>> generate a LOT of conducted noise, which passes through the 5V PS,
>> and
>>>>>>> the
>>>>>>>>> 3.3V regulator, and causing the microcontroller to crash.
>>>>>>>>> I did a bunch of tested and found that the noise is being conducted
>>>>>>>> through
>>>>>>>>> the wires back to the board through the PS, through the linear
>>>>>>> regulator,
>>>>>>>> and
>>>>>>>>> this is the 3.3V line...
>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
>>>>>>>>>
>>>>>>>>> I was over at someone else's place so did not have a lot of parts
>> with
>>>>>>> me,
>>>>>>>>> but...
>>>>>>>>> Adding a bunch more 0.1uf bypass capacitors all over the board did
>> not
>>>>>>>> help.
>>>>>>>>> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
>>>>>>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
>>>>> rate
>>>>>>>> of
>>>>>>>>> the crashing... but the ripple itself wasn't causing crashing.
>>>>>>>>>
>>>>>>>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC
>>>>> input
>>>>>>>> wires
>>>>>>>>> did not help.
>>>>>>>>> I then tried to create a crude/uncalculated LC filter (which
>> whatever
>>>>>>>>> components I had on hand (33uh inductor and 1000uf capacitor,
>> should
>>>>> be
>>>>>>>>> low ESR), then a Pi filter (added 680 uF capacitor), and those
>> barely
>>>>>>> made
>>>>>>>> a
>>>>>>>>> dent.
>>>>>>>>> Eventually I added another 0.1uf capacitor to the output side of
>> the
>>>>> pi
>>>>>>>> filter
>>>>>>>>> and that helped enough to prevent the microcontroller crashing.
>>>>>>>>> But there is still a lot of noise on the 3.3V line...
>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
>>>>>>>>>
>>>>>>>>> FWIW, this is where it ended up...
>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
>>>>>>>>>
>>>>>>>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
>>>>>>>>> I feel like smaller, low-ESR ceramic caps should help, but I doubt
>> it
>>>>>>> will
>>>>>>>> take
>>>>>>>>> out most of the noise.
>>>>>>>>> What is the right type of filter to eliminate this noise?
>>>>>>>>>
>>>>>>>>> Cheers,
>>>>>>>>> -Neil.
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>>>>>> View/change your membership options at
>>>>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>>>>> --
>>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>>>> View/change your membership options at
>>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>>>>>
>>>>> --
>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>> View/change your membership options at
>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>>>
>> --
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> http://mailman.mit.edu/mailman/listinfo/piclist
>>
>

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Re: [EE] Eliminating external noise through PS

Neil
In reply to this post by madscientistatlarge
Just mentioned that in another post (Grounded with regular lead/clip,
but prev tried paperclip mod and didn't see a change then so went back
to regular lead/clip), so will try it again.  Would be great if this was
the last bit of the issue.

By "float the scope", do you mean using a transformer of some sort to
isolate the ground?

Shielding the AC wires didn't make much of a dent... I first tried
aluminum foil and grounded on the motor side.  Then I tried actual
shielding braid, but that didn't do anything either.

I need to search for those packaged power entry filters.

Cheers,
-Neil.



On 12/29/2020 3:34 PM, madscientistatlarge wrote:

> When you measure with the scope, how are you grounding the Probe?  Those convenient wires with alligator clips make good antennas, best to take a wire, preferably beryllium copper because it's springy, and wrap one end around the exposed ground just behind the tip, then bend it to point the same way as the signal probe and trim to length so you are grounding it right where you are measuring.  Might also want to float the scope to avoid ground loops.  If you are in the U.S. These guys will sell a single foot of beryllium copper wire, <http://lfa-wire.com/Plated-Wire-article/Plated-Wire-2.html>.  Haven't dealt with them but plan to as soon as I get my bench setup.  I learned this trick on a job and have seen it mentioned once online (been online since 2000).  In a pinch a piece of copper might work briefly, or any other stiff wire, possibly even a paper clip in a pinch (haven't tried it, steel does have some resistance but likely not too bad on 1cm or less).  When you cut the wire you can cut a nice point on the end.
>
> Noise will drive one batty, I once traced it to a leaky transformer in a flow controller.  The current was going to ground through the computer's data acq card and sporadically making noise on the measurement.   No permanent effect in that case.  Thing was when I connected the scope ground to the equipment it took the leakage and the noise went away, only saw it because I reasoned the scope was doing the magic.  Opened the flow controller case and out of 4 transformers (1 for each channel) one had a big bubble on the encapsulation, I've always assumed it was spike damage.  Replaced the transformer and away went the noise.  The annoying thing is it had been in to the manufacturer for the noise problem and of course they found no issues (I don't blame them, I spent a day and a half playing with it before I figured it out).
>
> When you grab the lead and the noise drops you're probably being a lossy load, or getting phase cancellation, or???  In a pinch you could use shielded wiring to the motor, conduit might help enough, preferably grounded at only the motor (noise source) end of the line.  Also unless your' filters are shielded, and the line to/from them noise can easily couple around the filter.  This happens with power entry filtering if the wires run near each other, which makes the packaged power entry filters worth the extra $$ in many cases.
>
>
> Sent with ProtonMail Secure Email.
>
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Tuesday, December 29, 2020 12:36 PM, Jason White <[hidden email]> wrote:
>
>> My experience developing "all discrete" (no microcontroller) motor driver
>> PCBs is that any noise that is unaffected by filtering tends to be a
>> measurement or environmental artifact.
>>
>> I'd recommend doubled checking your probe/scope grounding - it is an
>> endless source of trouble and erroneous readings. I've found that often
>> times problems in systems are a result of a combination of "innocent
>> looking" and unrelated things that end up interacting in unexpected ways.
>>
>> On Tuesday, December 29, 2020, Neil [hidden email] wrote:
>>
>>> Happy holidays everyone.
>>> Okay, I got back to this recently and have a bunch of updates:
>>> For the tl;dr 'ers... I've got a lot of noise out, the processor does
>>> not crash anymore, but 2 questions remain:
>>>

>>> -   Should I have the AC-outlet ground wire, coming onto the PCB and used
>>>      as a shield?
>>>
>>> -   If I hold the AC wire with my hand, the noise (as seen on the
>>>      oscilloscope) drops (noticeably). Shielding the AC wire does not have
>>>      the same effect, so what is happening here, and how can I use this to
>>>      help reduce the noise even more?
>>>
>>>
>>> For the gory details, here's my summary of what I tried and found...
>>> For reference...
>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
>>> noise is mostly in the few Mhz range and higher.
>>>
>>> -   Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
>>> -   Low-pass filter helped minimally
>>> -   Pi filter was a bit better, but still small impact.
>>> -   Common mode choke (uncalculated, but should've been able to separate
>>>      60Hz from Mhz-range noise) didn't help. I am new to these, but
>>>      apparently above some frequency the impedance drops again.
>>>
>>> -   Ferrite across AC side of motor wires helped minimally.
>>> -   Ferrite on incoming-power AC wires did not help
>>> -   Removed relay (and jumper across contacts to run the pump) to see if
>>>      noise was coming into board from that side, but nope.
>>>
>>> -   Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
>>>      with wires soldered on for the incoming power and parallel wires to run
>>>      the pump, and a 1k load resistor on the PS output. Still a lot of noise
>>>
>>> -   Low-pass filter again helped reduce noise minimally.
>>> -   Capacitance multiplier helped noticeably.
>>> -   2 more ceramic caps from each motor wire to ground/motor case (right
>>>      at the motor) helped noticeably.
>>>
>>> -   Twisted the AC wires to the motor tighter, and didn't really see any
>>>      difference.
>>>
>>> -   Back to original board, to use some of these, but too much voltage
>>>      drop on capacitance multiplier to be usable. I should calculate this
>>>      properly and find the right transistor for this.
>>>
>>>
>>> At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
>>> filter and the board isn't crashing, but I can still see some noise on
>>> the scope, which I'd like to reduce even more. Going to try a
>>> multi-stage pi/LC filter.
>>> But I'm curious how to use the "phenomenon" where holding the AC wire in
>>> my hand reduces noise noticeably, to help this.
>>> Thanks,
>>> -Neil.
>>> On 12/13/2020 7:15 PM, Neil wrote:
>>>
>>>> That's a definite possibility at this point. The original circuit
>>>> (prior version) worked great with 2 layers, but I needed 2oz copper to
>>>> handle the pump current.
>>>> Never version works just as great. Or I should say "worked", until
>>>> they decided to switch from the AC pump to this DC pump.
>>>> Cheers,
>>>> -Neil
>>>> On 12/13/2020 6:58 PM, Jason White wrote:
>>>>
>>>>> Neil, from the pictures it looks like you're using a 2 layer PCB. Have
>>>>> you
>>>>> considered a 4 layer PCB? A continuous dedicated ground plane layer
>>>>> would
>>>>> drastically reduce the loop area (and thus susceptibility to EMI) of
>>>>> your
>>>>> traces.
>>>>> Otherwise, it may be worth considering moving the relays to a separate
>>>>> board/area.
>>>>> On Sunday, December 13, 2020, Neil [hidden email] wrote:
>>>>>
>>>>>> I strongly feel so, because in my early tests, I:
>>>>>> (a) disconnected one of the pump wires (so the pump wouldn't run), and
>>>>>> it was (expectedly) very clean (on the scope).
>>>>>> (b) disconnected both of the pump wires and plugged it into the female
>>>>>> side of a PC power cord, so the pump ran, but was connected to 120VAC
>>>>>> from a different source. Very clean power again.
>>>>>> In both cases, all else stayed the same including where the wires were
>>>>>> draped, etc.
>>>>>> In other tests, I moved the scope, power lines, etc and no change to
>>>>>> the
>>>>>> noise on the line.
>>>>>> Either way, I haven't done my other tests yet since I took the pump
>>>>>> with
>>>>>> me, so I'll get to those this week.
>>>>>> Cheers,
>>>>>> -Neil.
>>>>>> On 12/11/2020 7:37 PM, Jason White wrote:
>>>>>>
>>>>>>> Hi Neil,
>>>>>>> This may be a silly question: are you sure that some of these voltage
>>>>>>> spikes that you've captured on the scope are not artifacts of your
>>>>>>> measurement setup? The loop formed by the ground wire/clip on a scope
>>>>>>> probe
>>>>>>> makes a very effective antenna. Maybe your power rail is cleaner than
>>>>>>> you
>>>>>>> think - in which case the true problem might be elsewhere.
>>>>>>> -Jason White
>>>>>>> On Fri, Dec 11, 2020 at 3:11 PM Neil [hidden email] wrote:
>>>>>>>
>>>>>>>> Sorry, disappeared for a couple days, but some quick answers to
>>>>>>>> everything for now, and my next steps:
>>>>>>>>
>>>>>>>> -   Yes I have flyback diodes. Highlighted with yellow here, just
>>>>>>>>      above
>>>>>>>>
>>>>>>>> the relays...
>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
>>>>>>>>
>>>>>>>> -   James & Russell, in that diagram also, I labeled the paths for
>>>>>>>>      power.
>>>>>>>>
>>>>>>>> The 5V to the relays is pretty much dedicated and 5V is on the top
>>>>>>>> layer, and (dedicated) ground for the relays on the bottom layer.
>>>>>>>> But
>>>>>>>> yes, it's right up against the AC section, but as many components
>>>>>>>> have
>>>>>>>> been removed now, I will push that far away.
>>>>>>>>
>>>>>>>> -   The 3.3V regulator has been getting a bit warmer than I like, so I
>>>>>>>>      have been planning to use a buck converter instead. But maybe I
>>>>>>>>      should
>>>>>>>>
>>>>>>>> run two 3.3V regulators instead? I would think that the buck
>>>>>>>> converter
>>>>>>>> would be pass less of the noise through.
>>>>>>>>
>>>>>>>> -   I ran over there quickly to pick up stuff and tried a crude
>>>>>>>>      (uncalculated) common-mode choke I made up from stuff I could find.
>>>>>>>>      Did
>>>>>>>>
>>>>>>>> not make in dent in the noise coming through.
>>>>>>>> See here...
>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
>>>>>>>>
>>>>>>>> -   I feel like Brent may be correct, that the noise may be coming from
>>>>>>>>      the relay side. The processor (ESP32) is resetting. I know it's
>>>>>>>>      not a
>>>>>>>>
>>>>>>>> firmware issue as it had zero crashes with the previous pump.
>>>>>>>> Adding some info:
>>>>>>>> The previous pump was a huge AC pump. This new pump is actually DC,
>>>>>>>> but
>>>>>>>> there's a bridge rectifier on the wires. So I'm now convinced that
>>>>>>>> the
>>>>>>>> noise is coming from brushes.
>>>>>>>> I brought the pump with me, and I have a new blank board. My plan
>>>>>>>> is to
>>>>>>>> reproduce just enough of the circuit to see the noise, and I can cut
>>>>>>>> and
>>>>>>>> re-route traces (the 5V & ground to the relays) to see if helps.
>>>>>>>> I will also add a ceramic capacitor to the pump wires (right at the
>>>>>>>> pump), and hope that helps. Plus twist the wires.
>>>>>>>> I'll be back with some results.
>>>>>>>> Cheers,
>>>>>>>> -Neil.
>>>>>>>> On 12/10/2020 7:28 PM, FTL wrote:
>>>>>>>>
>>>>>>>>> This is almost too obvious, but in the schematic I do not see a
>>>>>>>>> flyback
>>>>>>>>> diode across the relay to suppress the back EMF when the relay is
>>>>>>>>> turned
>>>>>>>>> off. The lack of diode would cause a serious spike in the 5V supply
>>>>>>>>> when
>>>>>>>> the
>>>>>>>>
>>>>>>>>> relay is turned off.
>>>>>>>>> Is the transistor being turned on hard enough to keep the relay on
>>>>>>>>> properly.
>>>>>>>>> If it is not fully on with no flyback diode, maybe it is
>>>>>>>>> occasionally
>>>>>>>>> releasing and causing big noise on the 5V bus.
>>>>>>>>>
>>>>>>>>>> -----Original Message-----
>>>>>>>>>> From: [hidden email] [hidden email] On Behalf
>>>>>>>>>> Of
>>>>>>>> Neil
>>>>>>>>
>>>>>>>>>> Sent: December 8, 2020 11:04 AM
>>>>>>>>>> To: Microcontroller discussion list - Public. [hidden email]
>>>>>>>>>> Subject: [EE] Eliminating external noise through PS
>>>>>>>>>> Hi,
>>>>>>>>>> I'm working on a device that takes 120VAC, converts to 5VDC with a
>>>>>>>>>> PCB-
>>>>>>>>>> mounted power supply, then further reduces that to 3.3VDC with a
>>>>>>>>>> linear
>>>>>>>>>> regulator.
>>>>>>>>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
>>>>>>>>>> Overview...
>>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
>>>>>>>>>> All has been great until we switched to a specific pump, which
>>>>>>>>>> happens
>>>>>>>> to
>>>>>>>>
>>>>>>>>>> generate a LOT of conducted noise, which passes through the 5V PS,
>>>>>>>>>> and
>>>>>>>> the
>>>>>>>>
>>>>>>>>>> 3.3V regulator, and causing the microcontroller to crash.
>>>>>>>>>> I did a bunch of tested and found that the noise is being conducted
>>>>>>>>>> through
>>>>>>>>>> the wires back to the board through the PS, through the linear
>>>>>>>>>> regulator,
>>>>>>>>>> and
>>>>>>>>>> this is the 3.3V line...
>>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
>>>>>>>>>> I was over at someone else's place so did not have a lot of parts
>>>>>>>>>> with
>>>>>>>> me,
>>>>>>>>
>>>>>>>>>> but...
>>>>>>>>>> Adding a bunch more 0.1uf bypass capacitors all over the board did
>>>>>>>>>> not
>>>>>>>>> help.
>>>>>>>>>
>>>>>>>>>> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
>>>>>>>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
>>>>>>>>>> rate
>>>>>>>>> of
>>>>>>>>>
>>>>>>>>>> the crashing... but the ripple itself wasn't causing crashing.
>>>>>>>>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC
>>>>>>>>>> input
>>>>>>>>> wires
>>>>>>>>>
>>>>>>>>>> did not help.
>>>>>>>>>> I then tried to create a crude/uncalculated LC filter (which
>>>>>>>>>> whatever
>>>>>>>>>> components I had on hand (33uh inductor and 1000uf capacitor,
>>>>>>>>>> should
>>>>>> be
>>>>>>
>>>>>>>>>> low ESR), then a Pi filter (added 680 uF capacitor), and those
>>>>>>>>>> barely
>>>>>>>> made
>>>>>>>>
>>>>>>>>> a
>>>>>>>>>
>>>>>>>>>> dent.
>>>>>>>>>> Eventually I added another 0.1uf capacitor to the output side of
>>>>>>>>>> the
>>>>>> pi
>>>>>>
>>>>>>>>> filter
>>>>>>>>>
>>>>>>>>>> and that helped enough to prevent the microcontroller crashing.
>>>>>>>>>> But there is still a lot of noise on the 3.3V line...
>>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
>>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
>>>>>>>>>> FWIW, this is where it ended up...
>>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
>>>>>>>>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
>>>>>>>>>> I feel like smaller, low-ESR ceramic caps should help, but I doubt
>>>>>>>>>> it
>>>>>>>> will
>>>>>>>>
>>>>>>>>> take
>>>>>>>>>
>>>>>>>>>> out most of the noise.
>>>>>>>>>> What is the right type of filter to eliminate this noise?
>>>>>>>>>> Cheers,
>>>>>>>>>> -Neil.
>>>>>>>>>> --
>>>>>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>>>>>>> View/change your membership options at
>>>>>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>>>>>>>> --
>>>>>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>>>>>>> View/change your membership options at
>>>>>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>>>> --
>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>>> View/change your membership options at
>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>> --
>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>> View/change your membership options at
>>> http://mailman.mit.edu/mailman/listinfo/piclist
>> --
>>
>> Jason White
>>
>> ------------
>>
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> http://mailman.mit.edu/mailman/listinfo/piclist
>
>



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Re: [EE] Eliminating external noise through PS

Neil
In reply to this post by David VanHorn-2
Interesting thought... 10k pullup to +3v3.




On 12/29/2020 5:13 PM, David VanHorn wrote:

> What's your reset circuit look like?   High enough impedances here can
> cause these problems.
>
> On Tue, Dec 29, 2020, 11:22 AM Neil <[hidden email]> wrote:
>
>> Happy holidays everyone.
>>
>> Okay, I got back to this recently and have a bunch of updates:
>>
>> For the tl;dr 'ers... I've got a lot of noise out, the processor does
>> not crash anymore, but 2 questions remain:
>>
>> - Should I have the AC-outlet ground wire, coming onto the PCB and used
>> as a shield?
>>
>> - If I hold the AC wire with my hand, the noise (as seen on the
>> oscilloscope) drops (noticeably).  Shielding the AC wire does not have
>> the same effect, so what is happening here, and how can I use this to
>> help reduce the noise even more?
>>
>>
>> For the gory details, here's my summary of what I tried and found...
>>
>> For reference...
>> http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
>> noise is mostly in the few Mhz range and higher.
>>
>> - Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
>> - Low-pass filter helped minimally
>> - Pi filter was a bit better, but still small impact.
>> - Common mode choke (uncalculated, but should've been able to separate
>> 60Hz from Mhz-range noise) didn't help.  I am new to these, but
>> apparently above some frequency the impedance drops again.
>> - Ferrite across AC side of motor wires helped minimally.
>> - Ferrite on incoming-power AC wires did not help
>> - Removed relay (and jumper across contacts to run the pump) to see if
>> noise was coming into board from that side, but nope.
>> - Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
>> with wires soldered on for the incoming power and parallel wires to run
>> the pump, and a 1k load resistor on the PS output. Still a lot of noise
>> - Low-pass filter again helped reduce noise minimally.
>> - Capacitance multiplier helped noticeably.
>> - 2 more ceramic caps from each motor wire to ground/motor case (right
>> at the motor) helped noticeably.
>> - Twisted the AC wires to the motor tighter, and didn't really see any
>> difference.
>> - Back to original board, to use some of these, but too much voltage
>> drop on capacitance multiplier to be usable.  I should calculate this
>> properly and find the right transistor for this.
>>
>> At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
>> filter and the board isn't crashing, but I can still see some noise on
>> the scope, which I'd like to reduce even more.  Going to try a
>> multi-stage pi/LC filter.
>>
>> But I'm curious how to use the "phenomenon" where holding the AC wire in
>> my hand reduces noise noticeably, to help this.
>>
>>
>> Thanks,
>> -Neil.
>>
>>
>>
>> On 12/13/2020 7:15 PM, Neil wrote:
>>> That's a definite possibility at this point.  The original circuit
>>> (prior version) worked great with 2 layers, but I needed 2oz copper to
>>> handle the pump current.
>>> Never version works just as great.  Or  I should say "worked", until
>>> they decided to switch from the AC pump to this DC pump.
>>>
>>> Cheers,
>>> -Neil
>>>
>>>
>>>
>>> On 12/13/2020 6:58 PM, Jason White wrote:
>>>> Neil, from the pictures it looks like you're using a 2 layer PCB. Have
>> you
>>>> considered a 4 layer PCB? A continuous dedicated ground plane layer
>> would
>>>> drastically reduce the loop area (and thus susceptibility to EMI) of
>> your
>>>> traces.
>>>>
>>>> Otherwise, it may be worth considering moving the relays to a separate
>>>> board/area.
>>>>
>>>> On Sunday, December 13, 2020, Neil <[hidden email]> wrote:
>>>>
>>>>> I strongly feel so, because in my early tests, I:
>>>>> (a) disconnected one of the pump wires (so the pump wouldn't run), and
>>>>> it was (expectedly) very clean (on the scope).
>>>>> (b) disconnected both of the pump wires and plugged it into the female
>>>>> side of a PC power cord, so the pump ran, but was connected to 120VAC
>>>>> from a different source.  Very clean power again.
>>>>> In both cases, all else stayed the same including where the wires were
>>>>> draped, etc.
>>>>>
>>>>> In other tests, I moved the scope, power lines, etc and no change to
>> the
>>>>> noise on the line.
>>>>>
>>>>> Either way, I haven't done my other tests yet since I took the pump
>> with
>>>>> me, so I'll get to those this week.
>>>>>
>>>>> Cheers,
>>>>> -Neil.
>>>>>
>>>>>
>>>>> On 12/11/2020 7:37 PM, Jason White wrote:
>>>>>> Hi Neil,
>>>>>>
>>>>>> This may be a silly question: are you sure that some of these voltage
>>>>>> spikes that you've captured on the scope are not artifacts of your
>>>>>> measurement setup? The loop formed by the ground wire/clip on a scope
>>>>> probe
>>>>>> makes a very effective antenna. Maybe your power rail is cleaner than
>> you
>>>>>> think - in which case the true problem might be elsewhere.
>>>>>>
>>>>>> -Jason White
>>>>>>
>>>>>> On Fri, Dec 11, 2020 at 3:11 PM Neil <[hidden email]> wrote:
>>>>>>
>>>>>>> Sorry, disappeared for a couple days, but some quick answers to
>>>>>>> everything for now, and my next steps:
>>>>>>>
>>>>>>> - Yes I have flyback diodes.   Highlighted with yellow here,  just
>> above
>>>>>>> the relays...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
>>>>>>> - James & Russell, in that diagram also, I labeled the paths for
>> power.
>>>>>>> The 5V to the relays is pretty much dedicated and 5V is on the top
>>>>>>> layer, and (dedicated) ground for the relays on the bottom layer.
>> But
>>>>>>> yes, it's right up against the AC section, but as many components
>> have
>>>>>>> been removed now, I will push that far away.
>>>>>>> - The 3.3V regulator has been getting a bit warmer than I like, so I
>>>>>>> have been planning to use a buck converter instead.  But maybe I
>> should
>>>>>>> run two 3.3V regulators instead?  I would think that the buck
>> converter
>>>>>>> would be pass less of the noise through.
>>>>>>> - I ran over there quickly to pick up stuff and tried a crude
>>>>>>> (uncalculated) common-mode choke I made up from stuff I could find.
>> Did
>>>>>>> not make in dent in the noise coming through.
>>>>>>> See here...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
>>>>>>> - I feel like Brent may be correct, that the noise may be coming from
>>>>>>> the relay side.  The processor (ESP32) is resetting.  I know it's
>> not a
>>>>>>> firmware issue as it had zero crashes with the previous pump.
>>>>>>>
>>>>>>>
>>>>>>> Adding some info:
>>>>>>> The previous pump was a huge AC pump.  This new pump is actually DC,
>> but
>>>>>>> there's a bridge rectifier on the wires.  So I'm now convinced that
>> the
>>>>>>> noise is coming from brushes.
>>>>>>> I brought the pump with me, and I have a new blank board.  My plan
>> is to
>>>>>>> reproduce just enough of the circuit to see the noise, and I can cut
>> and
>>>>>>> re-route traces (the 5V & ground to the relays) to see if helps.
>>>>>>> I will also add a ceramic capacitor to the pump wires (right at the
>>>>>>> pump), and hope that helps.  Plus twist the wires.
>>>>>>>
>>>>>>> I'll be back with some results.
>>>>>>>
>>>>>>> Cheers,
>>>>>>> -Neil.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 12/10/2020 7:28 PM, FTL wrote:
>>>>>>>> This is almost too obvious, but in the schematic I do not see a
>> flyback
>>>>>>>> diode across the relay to suppress the back EMF when the relay is
>>>>> turned
>>>>>>>> off. The lack of diode would cause a serious spike in the 5V supply
>>>>> when
>>>>>>> the
>>>>>>>> relay is turned off.
>>>>>>>>
>>>>>>>> Is the transistor being turned on hard enough to keep the relay on
>>>>>>> properly.
>>>>>>>> If it is not fully on with no flyback diode, maybe it is
>> occasionally
>>>>>>>> releasing and causing big noise on the 5V bus.
>>>>>>>>
>>>>>>>>> -----Original Message-----
>>>>>>>>> From: [hidden email] <[hidden email]> On Behalf
>> Of
>>>>>>> Neil
>>>>>>>>> Sent: December 8, 2020 11:04 AM
>>>>>>>>> To: Microcontroller discussion list - Public. <[hidden email]>
>>>>>>>>> Subject: [EE] Eliminating external noise through PS
>>>>>>>>>
>>>>>>>>> Hi,
>>>>>>>>>
>>>>>>>>> I'm working on a device that takes 120VAC, converts to 5VDC with a
>>>>> PCB-
>>>>>>>>> mounted power supply, then further reduces that to 3.3VDC with a
>>>>> linear
>>>>>>>>> regulator.
>>>>>>>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
>>>>>>>>> Overview...
>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
>>>>>>>>>
>>>>>>>>> All has been great until we switched to a specific pump, which
>> happens
>>>>>>> to
>>>>>>>>> generate a LOT of conducted noise, which passes through the 5V PS,
>> and
>>>>>>> the
>>>>>>>>> 3.3V regulator, and causing the microcontroller to crash.
>>>>>>>>> I did a bunch of tested and found that the noise is being conducted
>>>>>>>> through
>>>>>>>>> the wires back to the board through the PS, through the linear
>>>>>>> regulator,
>>>>>>>> and
>>>>>>>>> this is the 3.3V line...
>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
>>>>>>>>>
>>>>>>>>> I was over at someone else's place so did not have a lot of parts
>> with
>>>>>>> me,
>>>>>>>>> but...
>>>>>>>>> Adding a bunch more 0.1uf bypass capacitors all over the board did
>> not
>>>>>>>> help.
>>>>>>>>> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
>>>>>>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
>>>>> rate
>>>>>>>> of
>>>>>>>>> the crashing... but the ripple itself wasn't causing crashing.
>>>>>>>>>
>>>>>>>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC
>>>>> input
>>>>>>>> wires
>>>>>>>>> did not help.
>>>>>>>>> I then tried to create a crude/uncalculated LC filter (which
>> whatever
>>>>>>>>> components I had on hand (33uh inductor and 1000uf capacitor,
>> should
>>>>> be
>>>>>>>>> low ESR), then a Pi filter (added 680 uF capacitor), and those
>> barely
>>>>>>> made
>>>>>>>> a
>>>>>>>>> dent.
>>>>>>>>> Eventually I added another 0.1uf capacitor to the output side of
>> the
>>>>> pi
>>>>>>>> filter
>>>>>>>>> and that helped enough to prevent the microcontroller crashing.
>>>>>>>>> But there is still a lot of noise on the 3.3V line...
>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
>>>>>>>>>
>>>>>>>>> FWIW, this is where it ended up...
>>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
>>>>>>>>>
>>>>>>>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
>>>>>>>>> I feel like smaller, low-ESR ceramic caps should help, but I doubt
>> it
>>>>>>> will
>>>>>>>> take
>>>>>>>>> out most of the noise.
>>>>>>>>> What is the right type of filter to eliminate this noise?
>>>>>>>>>
>>>>>>>>> Cheers,
>>>>>>>>> -Neil.
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>>>>>> View/change your membership options at
>>>>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>>>>> --
>>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>>>> View/change your membership options at
>>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>>>>>
>>>>> --
>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>>>> View/change your membership options at
>>>>> http://mailman.mit.edu/mailman/listinfo/piclist
>>>>>
>> --
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> http://mailman.mit.edu/mailman/listinfo/piclist
>>

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Re: [EE] Eliminating external noise through PS

Neil
In reply to this post by Bob Blick-5
Hmmm... not a current clamp, but I probably have a current sensor. Only
thing is that it would most probably be a high range (few 10's of amps
at least).

I really need to research and get some better equipment one of these days.

Cheers,
-Neil.



On 12/29/2020 5:30 PM, Bob Blick wrote:

> Hi Neil,
>
> I've found that measuring current is quite often better than measuring voltage when seeking out noise problems. I can be less convenient to do but at least where wires enter and exit the board it can be quite useful. Do you have a current clamp you can attach to your scope?
>
> Cheerful regards, Bob
>
> ________________________________________
> From: [hidden email] <[hidden email]> on behalf of Neil
> Sent: Tuesday, December 29, 2020 10:20 AM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Eliminating external noise through PS
>
> Happy holidays everyone.
>
> Okay, I got back to this recently and have a bunch of updates:
>
> For the tl;dr 'ers... I've got a lot of noise out, the processor does
> not crash anymore, but 2 questions remain:
>
> - Should I have the AC-outlet ground wire, coming onto the PCB and used
> as a shield?
>
> - If I hold the AC wire with my hand, the noise (as seen on the
> oscilloscope) drops (noticeably).  Shielding the AC wire does not have
> the same effect, so what is happening here, and how can I use this to
> help reduce the noise even more?
>
>
> For the gory details, here's my summary of what I tried and found...
>
> For reference...
> http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
> noise is mostly in the few Mhz range and higher.
>
> - Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
> - Low-pass filter helped minimally
> - Pi filter was a bit better, but still small impact.
> - Common mode choke (uncalculated, but should've been able to separate
> 60Hz from Mhz-range noise) didn't help.  I am new to these, but
> apparently above some frequency the impedance drops again.
> - Ferrite across AC side of motor wires helped minimally.
> - Ferrite on incoming-power AC wires did not help
> - Removed relay (and jumper across contacts to run the pump) to see if
> noise was coming into board from that side, but nope.
> - Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
> with wires soldered on for the incoming power and parallel wires to run
> the pump, and a 1k load resistor on the PS output. Still a lot of noise
> - Low-pass filter again helped reduce noise minimally.
> - Capacitance multiplier helped noticeably.
> - 2 more ceramic caps from each motor wire to ground/motor case (right
> at the motor) helped noticeably.
> - Twisted the AC wires to the motor tighter, and didn't really see any
> difference.
> - Back to original board, to use some of these, but too much voltage
> drop on capacitance multiplier to be usable.  I should calculate this
> properly and find the right transistor for this.
>
> At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
> filter and the board isn't crashing, but I can still see some noise on
> the scope, which I'd like to reduce even more.  Going to try a
> multi-stage pi/LC filter.
>
> But I'm curious how to use the "phenomenon" where holding the AC wire in
> my hand reduces noise noticeably, to help this.
>
>
> Thanks,
> -Neil.
>
>
>
> On 12/13/2020 7:15 PM, Neil wrote:
>> That's a definite possibility at this point.  The original circuit
>> (prior version) worked great with 2 layers, but I needed 2oz copper to
>> handle the pump current.
>> Never version works just as great.  Or  I should say "worked", until
>> they decided to switch from the AC pump to this DC pump.
>>
>> Cheers,
>> -Neil
>>
>>
>>
>> On 12/13/2020 6:58 PM, Jason White wrote:
>>> Neil, from the pictures it looks like you're using a 2 layer PCB. Have you
>>> considered a 4 layer PCB? A continuous dedicated ground plane layer would
>>> drastically reduce the loop area (and thus susceptibility to EMI) of your
>>> traces.
>>>
>>> Otherwise, it may be worth considering moving the relays to a separate
>>> board/area.
>>>
>>> On Sunday, December 13, 2020, Neil <[hidden email]> wrote:
>>>
>>>> I strongly feel so, because in my early tests, I:
>>>> (a) disconnected one of the pump wires (so the pump wouldn't run), and
>>>> it was (expectedly) very clean (on the scope).
>>>> (b) disconnected both of the pump wires and plugged it into the female
>>>> side of a PC power cord, so the pump ran, but was connected to 120VAC
>>>> from a different source.  Very clean power again.
>>>> In both cases, all else stayed the same including where the wires were
>>>> draped, etc.
>>>>
>>>> In other tests, I moved the scope, power lines, etc and no change to the
>>>> noise on the line.
>>>>
>>>> Either way, I haven't done my other tests yet since I took the pump with
>>>> me, so I'll get to those this week.
>>>>
>>>> Cheers,
>>>> -Neil.
>>>>
>>>>
>>>> On 12/11/2020 7:37 PM, Jason White wrote:
>>>>> Hi Neil,
>>>>>
>>>>> This may be a silly question: are you sure that some of these voltage
>>>>> spikes that you've captured on the scope are not artifacts of your
>>>>> measurement setup? The loop formed by the ground wire/clip on a scope
>>>> probe
>>>>> makes a very effective antenna. Maybe your power rail is cleaner than you
>>>>> think - in which case the true problem might be elsewhere.
>>>>>
>>>>> -Jason White
>>>>>
>>>>> On Fri, Dec 11, 2020 at 3:11 PM Neil <[hidden email]> wrote:
>>>>>
>>>>>> Sorry, disappeared for a couple days, but some quick answers to
>>>>>> everything for now, and my next steps:
>>>>>>
>>>>>> - Yes I have flyback diodes.   Highlighted with yellow here,  just above
>>>>>> the relays...
>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
>>>>>> - James & Russell, in that diagram also, I labeled the paths for power.
>>>>>> The 5V to the relays is pretty much dedicated and 5V is on the top
>>>>>> layer, and (dedicated) ground for the relays on the bottom layer.  But
>>>>>> yes, it's right up against the AC section, but as many components have
>>>>>> been removed now, I will push that far away.
>>>>>> - The 3.3V regulator has been getting a bit warmer than I like, so I
>>>>>> have been planning to use a buck converter instead.  But maybe I should
>>>>>> run two 3.3V regulators instead?  I would think that the buck converter
>>>>>> would be pass less of the noise through.
>>>>>> - I ran over there quickly to pick up stuff and tried a crude
>>>>>> (uncalculated) common-mode choke I made up from stuff I could find. Did
>>>>>> not make in dent in the noise coming through.
>>>>>> See here...
>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
>>>>>> - I feel like Brent may be correct, that the noise may be coming from
>>>>>> the relay side.  The processor (ESP32) is resetting.  I know it's not a
>>>>>> firmware issue as it had zero crashes with the previous pump.
>>>>>>
>>>>>>
>>>>>> Adding some info:
>>>>>> The previous pump was a huge AC pump.  This new pump is actually DC, but
>>>>>> there's a bridge rectifier on the wires.  So I'm now convinced that the
>>>>>> noise is coming from brushes.
>>>>>> I brought the pump with me, and I have a new blank board.  My plan is to
>>>>>> reproduce just enough of the circuit to see the noise, and I can cut and
>>>>>> re-route traces (the 5V & ground to the relays) to see if helps.
>>>>>> I will also add a ceramic capacitor to the pump wires (right at the
>>>>>> pump), and hope that helps.  Plus twist the wires.
>>>>>>
>>>>>> I'll be back with some results.
>>>>>>
>>>>>> Cheers,
>>>>>> -Neil.
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 12/10/2020 7:28 PM, FTL wrote:
>>>>>>> This is almost too obvious, but in the schematic I do not see a flyback
>>>>>>> diode across the relay to suppress the back EMF when the relay is
>>>> turned
>>>>>>> off. The lack of diode would cause a serious spike in the 5V supply
>>>> when
>>>>>> the
>>>>>>> relay is turned off.
>>>>>>>
>>>>>>> Is the transistor being turned on hard enough to keep the relay on
>>>>>> properly.
>>>>>>> If it is not fully on with no flyback diode, maybe it is occasionally
>>>>>>> releasing and causing big noise on the 5V bus.
>>>>>>>
>>>>>>>> -----Original Message-----
>>>>>>>> From: [hidden email] <[hidden email]> On Behalf Of
>>>>>> Neil
>>>>>>>> Sent: December 8, 2020 11:04 AM
>>>>>>>> To: Microcontroller discussion list - Public. <[hidden email]>
>>>>>>>> Subject: [EE] Eliminating external noise through PS
>>>>>>>>
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> I'm working on a device that takes 120VAC, converts to 5VDC with a
>>>> PCB-
>>>>>>>> mounted power supply, then further reduces that to 3.3VDC with a
>>>> linear
>>>>>>>> regulator.
>>>>>>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
>>>>>>>> Overview...
>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
>>>>>>>>
>>>>>>>> All has been great until we switched to a specific pump, which happens
>>>>>> to
>>>>>>>> generate a LOT of conducted noise, which passes through the 5V PS, and
>>>>>> the
>>>>>>>> 3.3V regulator, and causing the microcontroller to crash.
>>>>>>>> I did a bunch of tested and found that the noise is being conducted
>>>>>>> through
>>>>>>>> the wires back to the board through the PS, through the linear
>>>>>> regulator,
>>>>>>> and
>>>>>>>> this is the 3.3V line...
>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
>>>>>>>>
>>>>>>>> I was over at someone else's place so did not have a lot of parts with
>>>>>> me,
>>>>>>>> but...
>>>>>>>> Adding a bunch more 0.1uf bypass capacitors all over the board did not
>>>>>>> help.
>>>>>>>> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
>>>>>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
>>>> rate
>>>>>>> of
>>>>>>>> the crashing... but the ripple itself wasn't causing crashing.
>>>>>>>>
>>>>>>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC
>>>> input
>>>>>>> wires
>>>>>>>> did not help.
>>>>>>>> I then tried to create a crude/uncalculated LC filter (which whatever
>>>>>>>> components I had on hand (33uh inductor and 1000uf capacitor, should
>>>> be
>>>>>>>> low ESR), then a Pi filter (added 680 uF capacitor), and those barely
>>>>>> made
>>>>>>> a
>>>>>>>> dent.
>>>>>>>> Eventually I added another 0.1uf capacitor to the output side of the
>>>> pi
>>>>>>> filter
>>>>>>>> and that helped enough to prevent the microcontroller crashing.
>>>>>>>> But there is still a lot of noise on the 3.3V line...
>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
>>>>>>>>
>>>>>>>> FWIW, this is where it ended up...
>>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
>>>>>>>>
>>>>>>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
>>>>>>>> I feel like smaller, low-ESR ceramic caps should help, but I doubt it
>>>>>> will
>>>>>>> take
>>>>>>>> out most of the noise.
>>>>>>>> What is the right type of filter to eliminate this noise?
>>>>>>>>
>>>>>>>> Cheers,
>>>>>>>> -Neil.

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Re: [EE] Eliminating external noise through PS

Jason White-20
Have you considered using the "poor man's" differential probe "trick" [1]
to assess (partially) if the noise is being picked up by your leads?

[1] https://www.eevblog.com/forum/beginners/poor-mans-differential-probe/



On Wednesday, December 30, 2020, Neil <[hidden email]> wrote:

> Hmmm... not a current clamp, but I probably have a current sensor. Only
> thing is that it would most probably be a high range (few 10's of amps
> at least).
>
> I really need to research and get some better equipment one of these days.
>
> Cheers,
> -Neil.
>
>
>
> On 12/29/2020 5:30 PM, Bob Blick wrote:
> > Hi Neil,
> >
> > I've found that measuring current is quite often better than measuring
> voltage when seeking out noise problems. I can be less convenient to do but
> at least where wires enter and exit the board it can be quite useful. Do
> you have a current clamp you can attach to your scope?
> >
> > Cheerful regards, Bob
> >
> > ________________________________________
> > From: [hidden email] <[hidden email]> on behalf of
> Neil
> > Sent: Tuesday, December 29, 2020 10:20 AM
> > To: Microcontroller discussion list - Public.
> > Subject: Re: [EE] Eliminating external noise through PS
> >
> > Happy holidays everyone.
> >
> > Okay, I got back to this recently and have a bunch of updates:
> >
> > For the tl;dr 'ers... I've got a lot of noise out, the processor does
> > not crash anymore, but 2 questions remain:
> >
> > - Should I have the AC-outlet ground wire, coming onto the PCB and used
> > as a shield?
> >
> > - If I hold the AC wire with my hand, the noise (as seen on the
> > oscilloscope) drops (noticeably).  Shielding the AC wire does not have
> > the same effect, so what is happening here, and how can I use this to
> > help reduce the noise even more?
> >
> >
> > For the gory details, here's my summary of what I tried and found...
> >
> > For reference...
> > http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
> > noise is mostly in the few Mhz range and higher.
> >
> > - Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
> > - Low-pass filter helped minimally
> > - Pi filter was a bit better, but still small impact.
> > - Common mode choke (uncalculated, but should've been able to separate
> > 60Hz from Mhz-range noise) didn't help.  I am new to these, but
> > apparently above some frequency the impedance drops again.
> > - Ferrite across AC side of motor wires helped minimally.
> > - Ferrite on incoming-power AC wires did not help
> > - Removed relay (and jumper across contacts to run the pump) to see if
> > noise was coming into board from that side, but nope.
> > - Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
> > with wires soldered on for the incoming power and parallel wires to run
> > the pump, and a 1k load resistor on the PS output. Still a lot of noise
> > - Low-pass filter again helped reduce noise minimally.
> > - Capacitance multiplier helped noticeably.
> > - 2 more ceramic caps from each motor wire to ground/motor case (right
> > at the motor) helped noticeably.
> > - Twisted the AC wires to the motor tighter, and didn't really see any
> > difference.
> > - Back to original board, to use some of these, but too much voltage
> > drop on capacitance multiplier to be usable.  I should calculate this
> > properly and find the right transistor for this.
> >
> > At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
> > filter and the board isn't crashing, but I can still see some noise on
> > the scope, which I'd like to reduce even more.  Going to try a
> > multi-stage pi/LC filter.
> >
> > But I'm curious how to use the "phenomenon" where holding the AC wire in
> > my hand reduces noise noticeably, to help this.
> >
> >
> > Thanks,
> > -Neil.
> >
> >
> >
> > On 12/13/2020 7:15 PM, Neil wrote:
> >> That's a definite possibility at this point.  The original circuit
> >> (prior version) worked great with 2 layers, but I needed 2oz copper to
> >> handle the pump current.
> >> Never version works just as great.  Or  I should say "worked", until
> >> they decided to switch from the AC pump to this DC pump.
> >>
> >> Cheers,
> >> -Neil
> >>
> >>
> >>
> >> On 12/13/2020 6:58 PM, Jason White wrote:
> >>> Neil, from the pictures it looks like you're using a 2 layer PCB. Have
> you
> >>> considered a 4 layer PCB? A continuous dedicated ground plane layer
> would
> >>> drastically reduce the loop area (and thus susceptibility to EMI) of
> your
> >>> traces.
> >>>
> >>> Otherwise, it may be worth considering moving the relays to a separate
> >>> board/area.
> >>>
> >>> On Sunday, December 13, 2020, Neil <[hidden email]> wrote:
> >>>
> >>>> I strongly feel so, because in my early tests, I:
> >>>> (a) disconnected one of the pump wires (so the pump wouldn't run), and
> >>>> it was (expectedly) very clean (on the scope).
> >>>> (b) disconnected both of the pump wires and plugged it into the female
> >>>> side of a PC power cord, so the pump ran, but was connected to 120VAC
> >>>> from a different source.  Very clean power again.
> >>>> In both cases, all else stayed the same including where the wires were
> >>>> draped, etc.
> >>>>
> >>>> In other tests, I moved the scope, power lines, etc and no change to
> the
> >>>> noise on the line.
> >>>>
> >>>> Either way, I haven't done my other tests yet since I took the pump
> with
> >>>> me, so I'll get to those this week.
> >>>>
> >>>> Cheers,
> >>>> -Neil.
> >>>>
> >>>>
> >>>> On 12/11/2020 7:37 PM, Jason White wrote:
> >>>>> Hi Neil,
> >>>>>
> >>>>> This may be a silly question: are you sure that some of these voltage
> >>>>> spikes that you've captured on the scope are not artifacts of your
> >>>>> measurement setup? The loop formed by the ground wire/clip on a scope
> >>>> probe
> >>>>> makes a very effective antenna. Maybe your power rail is cleaner
> than you
> >>>>> think - in which case the true problem might be elsewhere.
> >>>>>
> >>>>> -Jason White
> >>>>>
> >>>>> On Fri, Dec 11, 2020 at 3:11 PM Neil <[hidden email]> wrote:
> >>>>>
> >>>>>> Sorry, disappeared for a couple days, but some quick answers to
> >>>>>> everything for now, and my next steps:
> >>>>>>
> >>>>>> - Yes I have flyback diodes.   Highlighted with yellow here,  just
> above
> >>>>>> the relays...
> >>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
> >>>>>> - James & Russell, in that diagram also, I labeled the paths for
> power.
> >>>>>> The 5V to the relays is pretty much dedicated and 5V is on the top
> >>>>>> layer, and (dedicated) ground for the relays on the bottom layer.
> But
> >>>>>> yes, it's right up against the AC section, but as many components
> have
> >>>>>> been removed now, I will push that far away.
> >>>>>> - The 3.3V regulator has been getting a bit warmer than I like, so I
> >>>>>> have been planning to use a buck converter instead.  But maybe I
> should
> >>>>>> run two 3.3V regulators instead?  I would think that the buck
> converter
> >>>>>> would be pass less of the noise through.
> >>>>>> - I ran over there quickly to pick up stuff and tried a crude
> >>>>>> (uncalculated) common-mode choke I made up from stuff I could find.
> Did
> >>>>>> not make in dent in the noise coming through.
> >>>>>> See here...
> >>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
> >>>>>> - I feel like Brent may be correct, that the noise may be coming
> from
> >>>>>> the relay side.  The processor (ESP32) is resetting.  I know it's
> not a
> >>>>>> firmware issue as it had zero crashes with the previous pump.
> >>>>>>
> >>>>>>
> >>>>>> Adding some info:
> >>>>>> The previous pump was a huge AC pump.  This new pump is actually
> DC, but
> >>>>>> there's a bridge rectifier on the wires.  So I'm now convinced that
> the
> >>>>>> noise is coming from brushes.
> >>>>>> I brought the pump with me, and I have a new blank board.  My plan
> is to
> >>>>>> reproduce just enough of the circuit to see the noise, and I can
> cut and
> >>>>>> re-route traces (the 5V & ground to the relays) to see if helps.
> >>>>>> I will also add a ceramic capacitor to the pump wires (right at the
> >>>>>> pump), and hope that helps.  Plus twist the wires.
> >>>>>>
> >>>>>> I'll be back with some results.
> >>>>>>
> >>>>>> Cheers,
> >>>>>> -Neil.
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> On 12/10/2020 7:28 PM, FTL wrote:
> >>>>>>> This is almost too obvious, but in the schematic I do not see a
> flyback
> >>>>>>> diode across the relay to suppress the back EMF when the relay is
> >>>> turned
> >>>>>>> off. The lack of diode would cause a serious spike in the 5V supply
> >>>> when
> >>>>>> the
> >>>>>>> relay is turned off.
> >>>>>>>
> >>>>>>> Is the transistor being turned on hard enough to keep the relay on
> >>>>>> properly.
> >>>>>>> If it is not fully on with no flyback diode, maybe it is
> occasionally
> >>>>>>> releasing and causing big noise on the 5V bus.
> >>>>>>>
> >>>>>>>> -----Original Message-----
> >>>>>>>> From: [hidden email] <[hidden email]> On
> Behalf Of
> >>>>>> Neil
> >>>>>>>> Sent: December 8, 2020 11:04 AM
> >>>>>>>> To: Microcontroller discussion list - Public. <[hidden email]>
> >>>>>>>> Subject: [EE] Eliminating external noise through PS
> >>>>>>>>
> >>>>>>>> Hi,
> >>>>>>>>
> >>>>>>>> I'm working on a device that takes 120VAC, converts to 5VDC with a
> >>>> PCB-
> >>>>>>>> mounted power supply, then further reduces that to 3.3VDC with a
> >>>> linear
> >>>>>>>> regulator.
> >>>>>>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
> >>>>>>>> Overview...
> >>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
> >>>>>>>>
> >>>>>>>> All has been great until we switched to a specific pump, which
> happens
> >>>>>> to
> >>>>>>>> generate a LOT of conducted noise, which passes through the 5V
> PS, and
> >>>>>> the
> >>>>>>>> 3.3V regulator, and causing the microcontroller to crash.
> >>>>>>>> I did a bunch of tested and found that the noise is being
> conducted
> >>>>>>> through
> >>>>>>>> the wires back to the board through the PS, through the linear
> >>>>>> regulator,
> >>>>>>> and
> >>>>>>>> this is the 3.3V line...
> >>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
> >>>>>>>>
> >>>>>>>> I was over at someone else's place so did not have a lot of parts
> with
> >>>>>> me,
> >>>>>>>> but...
> >>>>>>>> Adding a bunch more 0.1uf bypass capacitors all over the board
> did not
> >>>>>>> help.
> >>>>>>>> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
> >>>>>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce
> the
> >>>> rate
> >>>>>>> of
> >>>>>>>> the crashing... but the ripple itself wasn't causing crashing.
> >>>>>>>>
> >>>>>>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC
> >>>> input
> >>>>>>> wires
> >>>>>>>> did not help.
> >>>>>>>> I then tried to create a crude/uncalculated LC filter (which
> whatever
> >>>>>>>> components I had on hand (33uh inductor and 1000uf capacitor,
> should
> >>>> be
> >>>>>>>> low ESR), then a Pi filter (added 680 uF capacitor), and those
> barely
> >>>>>> made
> >>>>>>> a
> >>>>>>>> dent.
> >>>>>>>> Eventually I added another 0.1uf capacitor to the output side of
> the
> >>>> pi
> >>>>>>> filter
> >>>>>>>> and that helped enough to prevent the microcontroller crashing.
> >>>>>>>> But there is still a lot of noise on the 3.3V line...
> >>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
> >>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
> >>>>>>>>
> >>>>>>>> FWIW, this is where it ended up...
> >>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
> >>>>>>>>
> >>>>>>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
> >>>>>>>> I feel like smaller, low-ESR ceramic caps should help, but I
> doubt it
> >>>>>> will
> >>>>>>> take
> >>>>>>>> out most of the noise.
> >>>>>>>> What is the right type of filter to eliminate this noise?
> >>>>>>>>
> >>>>>>>> Cheers,
> >>>>>>>> -Neil.
>
> --
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Re: [EE] Eliminating external noise through PS

madscientistatlarge
In reply to this post by Neil
No, I meant using what in America, is a "grounding adapter", meant to convert 2 wire to 3 wire grounded outlets but useful for breaking ground loops if you don't connect the ground wire.  Of course this defeats a safety feature and should be done with care.  Basic idea is to not ground the scope through the power plug but rather through the probes connection.


Sent with ProtonMail Secure Email.

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Wednesday, December 30, 2020 5:22 PM, Neil <[hidden email]> wrote:

> Just mentioned that in another post (Grounded with regular lead/clip,
> but prev tried paperclip mod and didn't see a change then so went back
> to regular lead/clip), so will try it again. Would be great if this was
> the last bit of the issue.
>
> By "float the scope", do you mean using a transformer of some sort to
> isolate the ground?
>
> Shielding the AC wires didn't make much of a dent... I first tried
> aluminum foil and grounded on the motor side. Then I tried actual
> shielding braid, but that didn't do anything either.
>
> I need to search for those packaged power entry filters.
>
> Cheers,
> -Neil.
>
> On 12/29/2020 3:34 PM, madscientistatlarge wrote:
>
> > When you measure with the scope, how are you grounding the Probe? Those convenient wires with alligator clips make good antennas, best to take a wire, preferably beryllium copper because it's springy, and wrap one end around the exposed ground just behind the tip, then bend it to point the same way as the signal probe and trim to length so you are grounding it right where you are measuring. Might also want to float the scope to avoid ground loops. If you are in the U.S. These guys will sell a single foot of beryllium copper wire, http://lfa-wire.com/Plated-Wire-article/Plated-Wire-2.html. Haven't dealt with them but plan to as soon as I get my bench setup. I learned this trick on a job and have seen it mentioned once online (been online since 2000). In a pinch a piece of copper might work briefly, or any other stiff wire, possibly even a paper clip in a pinch (haven't tried it, steel does have some resistance but likely not too bad on 1cm or less). When you cut the wire you can cut a nice point on the end.
> > Noise will drive one batty, I once traced it to a leaky transformer in a flow controller. The current was going to ground through the computer's data acq card and sporadically making noise on the measurement. No permanent effect in that case. Thing was when I connected the scope ground to the equipment it took the leakage and the noise went away, only saw it because I reasoned the scope was doing the magic. Opened the flow controller case and out of 4 transformers (1 for each channel) one had a big bubble on the encapsulation, I've always assumed it was spike damage. Replaced the transformer and away went the noise. The annoying thing is it had been in to the manufacturer for the noise problem and of course they found no issues (I don't blame them, I spent a day and a half playing with it before I figured it out).
> > When you grab the lead and the noise drops you're probably being a lossy load, or getting phase cancellation, or??? In a pinch you could use shielded wiring to the motor, conduit might help enough, preferably grounded at only the motor (noise source) end of the line. Also unless your' filters are shielded, and the line to/from them noise can easily couple around the filter. This happens with power entry filtering if the wires run near each other, which makes the packaged power entry filters worth the extra $$ in many cases.
> > Sent with ProtonMail Secure Email.
> > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> > On Tuesday, December 29, 2020 12:36 PM, Jason White [hidden email] wrote:
> >
> > > My experience developing "all discrete" (no microcontroller) motor driver
> > > PCBs is that any noise that is unaffected by filtering tends to be a
> > > measurement or environmental artifact.
> > > I'd recommend doubled checking your probe/scope grounding - it is an
> > > endless source of trouble and erroneous readings. I've found that often
> > > times problems in systems are a result of a combination of "innocent
> > > looking" and unrelated things that end up interacting in unexpected ways.
> > > On Tuesday, December 29, 2020, Neil [hidden email] wrote:
> > >
> > > > Happy holidays everyone.
> > > > Okay, I got back to this recently and have a bunch of updates:
> > > > For the tl;dr 'ers... I've got a lot of noise out, the processor does
> > > > not crash anymore, but 2 questions remain:
>
> > > > -   Should I have the AC-outlet ground wire, coming onto the PCB and used
> > > >     as a shield?
> > > >
> > > > -   If I hold the AC wire with my hand, the noise (as seen on the
> > > >     oscilloscope) drops (noticeably). Shielding the AC wire does not have
> > > >     the same effect, so what is happening here, and how can I use this to
> > > >     help reduce the noise even more?
> > > >
> > > >
> > > > For the gory details, here's my summary of what I tried and found...
> > > > For reference...
> > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
> > > > noise is mostly in the few Mhz range and higher.
> > > >
> > > > -   Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
> > > >
> > > > -   Low-pass filter helped minimally
> > > >
> > > > -   Pi filter was a bit better, but still small impact.
> > > >
> > > > -   Common mode choke (uncalculated, but should've been able to separate
> > > >     60Hz from Mhz-range noise) didn't help. I am new to these, but
> > > >     apparently above some frequency the impedance drops again.
> > > >
> > > > -   Ferrite across AC side of motor wires helped minimally.
> > > >
> > > > -   Ferrite on incoming-power AC wires did not help
> > > >
> > > > -   Removed relay (and jumper across contacts to run the pump) to see if
> > > >     noise was coming into board from that side, but nope.
> > > >
> > > > -   Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
> > > >     with wires soldered on for the incoming power and parallel wires to run
> > > >     the pump, and a 1k load resistor on the PS output. Still a lot of noise
> > > >
> > > > -   Low-pass filter again helped reduce noise minimally.
> > > >
> > > > -   Capacitance multiplier helped noticeably.
> > > >
> > > > -   2 more ceramic caps from each motor wire to ground/motor case (right
> > > >     at the motor) helped noticeably.
> > > >
> > > > -   Twisted the AC wires to the motor tighter, and didn't really see any
> > > >     difference.
> > > >
> > > > -   Back to original board, to use some of these, but too much voltage
> > > >     drop on capacitance multiplier to be usable. I should calculate this
> > > >     properly and find the right transistor for this.
> > > >
> > > >
> > > > At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
> > > > filter and the board isn't crashing, but I can still see some noise on
> > > > the scope, which I'd like to reduce even more. Going to try a
> > > > multi-stage pi/LC filter.
> > > > But I'm curious how to use the "phenomenon" where holding the AC wire in
> > > > my hand reduces noise noticeably, to help this.
> > > > Thanks,
> > > > -Neil.
> > > > On 12/13/2020 7:15 PM, Neil wrote:
> > > >
> > > > > That's a definite possibility at this point. The original circuit
> > > > > (prior version) worked great with 2 layers, but I needed 2oz copper to
> > > > > handle the pump current.
> > > > > Never version works just as great. Or I should say "worked", until
> > > > > they decided to switch from the AC pump to this DC pump.
> > > > > Cheers,
> > > > > -Neil
> > > > > On 12/13/2020 6:58 PM, Jason White wrote:
> > > > >
> > > > > > Neil, from the pictures it looks like you're using a 2 layer PCB. Have
> > > > > > you
> > > > > > considered a 4 layer PCB? A continuous dedicated ground plane layer
> > > > > > would
> > > > > > drastically reduce the loop area (and thus susceptibility to EMI) of
> > > > > > your
> > > > > > traces.
> > > > > > Otherwise, it may be worth considering moving the relays to a separate
> > > > > > board/area.
> > > > > > On Sunday, December 13, 2020, Neil [hidden email] wrote:
> > > > > >
> > > > > > > I strongly feel so, because in my early tests, I:
> > > > > > > (a) disconnected one of the pump wires (so the pump wouldn't run), and
> > > > > > > it was (expectedly) very clean (on the scope).
> > > > > > > (b) disconnected both of the pump wires and plugged it into the female
> > > > > > > side of a PC power cord, so the pump ran, but was connected to 120VAC
> > > > > > > from a different source. Very clean power again.
> > > > > > > In both cases, all else stayed the same including where the wires were
> > > > > > > draped, etc.
> > > > > > > In other tests, I moved the scope, power lines, etc and no change to
> > > > > > > the
> > > > > > > noise on the line.
> > > > > > > Either way, I haven't done my other tests yet since I took the pump
> > > > > > > with
> > > > > > > me, so I'll get to those this week.
> > > > > > > Cheers,
> > > > > > > -Neil.
> > > > > > > On 12/11/2020 7:37 PM, Jason White wrote:
> > > > > > >
> > > > > > > > Hi Neil,
> > > > > > > > This may be a silly question: are you sure that some of these voltage
> > > > > > > > spikes that you've captured on the scope are not artifacts of your
> > > > > > > > measurement setup? The loop formed by the ground wire/clip on a scope
> > > > > > > > probe
> > > > > > > > makes a very effective antenna. Maybe your power rail is cleaner than
> > > > > > > > you
> > > > > > > > think - in which case the true problem might be elsewhere.
> > > > > > > > -Jason White
> > > > > > > > On Fri, Dec 11, 2020 at 3:11 PM Neil [hidden email] wrote:
> > > > > > > >
> > > > > > > > > Sorry, disappeared for a couple days, but some quick answers to
> > > > > > > > > everything for now, and my next steps:
> > > > > > > > >
> > > > > > > > > -   Yes I have flyback diodes. Highlighted with yellow here, just
> > > > > > > > >     above
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > the relays...
> > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
> > > > > > > > >
> > > > > > > > > -   James & Russell, in that diagram also, I labeled the paths for
> > > > > > > > >     power.
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > The 5V to the relays is pretty much dedicated and 5V is on the top
> > > > > > > > > layer, and (dedicated) ground for the relays on the bottom layer.
> > > > > > > > > But
> > > > > > > > > yes, it's right up against the AC section, but as many components
> > > > > > > > > have
> > > > > > > > > been removed now, I will push that far away.
> > > > > > > > >
> > > > > > > > > -   The 3.3V regulator has been getting a bit warmer than I like, so I
> > > > > > > > >     have been planning to use a buck converter instead. But maybe I
> > > > > > > > >     should
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > run two 3.3V regulators instead? I would think that the buck
> > > > > > > > > converter
> > > > > > > > > would be pass less of the noise through.
> > > > > > > > >
> > > > > > > > > -   I ran over there quickly to pick up stuff and tried a crude
> > > > > > > > >     (uncalculated) common-mode choke I made up from stuff I could find.
> > > > > > > > >     Did
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > not make in dent in the noise coming through.
> > > > > > > > > See here...
> > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
> > > > > > > > >
> > > > > > > > > -   I feel like Brent may be correct, that the noise may be coming from
> > > > > > > > >     the relay side. The processor (ESP32) is resetting. I know it's
> > > > > > > > >     not a
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > firmware issue as it had zero crashes with the previous pump.
> > > > > > > > > Adding some info:
> > > > > > > > > The previous pump was a huge AC pump. This new pump is actually DC,
> > > > > > > > > but
> > > > > > > > > there's a bridge rectifier on the wires. So I'm now convinced that
> > > > > > > > > the
> > > > > > > > > noise is coming from brushes.
> > > > > > > > > I brought the pump with me, and I have a new blank board. My plan
> > > > > > > > > is to
> > > > > > > > > reproduce just enough of the circuit to see the noise, and I can cut
> > > > > > > > > and
> > > > > > > > > re-route traces (the 5V & ground to the relays) to see if helps.
> > > > > > > > > I will also add a ceramic capacitor to the pump wires (right at the
> > > > > > > > > pump), and hope that helps. Plus twist the wires.
> > > > > > > > > I'll be back with some results.
> > > > > > > > > Cheers,
> > > > > > > > > -Neil.
> > > > > > > > > On 12/10/2020 7:28 PM, FTL wrote:
> > > > > > > > >
> > > > > > > > > > This is almost too obvious, but in the schematic I do not see a
> > > > > > > > > > flyback
> > > > > > > > > > diode across the relay to suppress the back EMF when the relay is
> > > > > > > > > > turned
> > > > > > > > > > off. The lack of diode would cause a serious spike in the 5V supply
> > > > > > > > > > when
> > > > > > > > > > the
> > > > > > > > >
> > > > > > > > > > relay is turned off.
> > > > > > > > > > Is the transistor being turned on hard enough to keep the relay on
> > > > > > > > > > properly.
> > > > > > > > > > If it is not fully on with no flyback diode, maybe it is
> > > > > > > > > > occasionally
> > > > > > > > > > releasing and causing big noise on the 5V bus.
> > > > > > > > > >
> > > > > > > > > > > -----Original Message-----
> > > > > > > > > > > From: [hidden email] [hidden email] On Behalf
> > > > > > > > > > > Of
> > > > > > > > > > > Neil
> > > > > > > > >
> > > > > > > > > > > Sent: December 8, 2020 11:04 AM
> > > > > > > > > > > To: Microcontroller discussion list - Public. [hidden email]
> > > > > > > > > > > Subject: [EE] Eliminating external noise through PS
> > > > > > > > > > > Hi,
> > > > > > > > > > > I'm working on a device that takes 120VAC, converts to 5VDC with a
> > > > > > > > > > > PCB-
> > > > > > > > > > > mounted power supply, then further reduces that to 3.3VDC with a
> > > > > > > > > > > linear
> > > > > > > > > > > regulator.
> > > > > > > > > > > A 3.3V microcontroller switches a relay to power a 120VAC pump.
> > > > > > > > > > > Overview...
> > > > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
> > > > > > > > > > > All has been great until we switched to a specific pump, which
> > > > > > > > > > > happens
> > > > > > > > > > > to
> > > > > > > > >
> > > > > > > > > > > generate a LOT of conducted noise, which passes through the 5V PS,
> > > > > > > > > > > and
> > > > > > > > > > > the
> > > > > > > > >
> > > > > > > > > > > 3.3V regulator, and causing the microcontroller to crash.
> > > > > > > > > > > I did a bunch of tested and found that the noise is being conducted
> > > > > > > > > > > through
> > > > > > > > > > > the wires back to the board through the PS, through the linear
> > > > > > > > > > > regulator,
> > > > > > > > > > > and
> > > > > > > > > > > this is the 3.3V line...
> > > > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
> > > > > > > > > > > I was over at someone else's place so did not have a lot of parts
> > > > > > > > > > > with
> > > > > > > > > > > me,
> > > > > > > > >
> > > > > > > > > > > but...
> > > > > > > > > > > Adding a bunch more 0.1uf bypass capacitors all over the board did
> > > > > > > > > > > not
> > > > > > > > > > > help.
> > > > > > > > > >
> > > > > > > > > > > Changing the power supply from an IRM-10-5 (industrial spec, 200mV
> > > > > > > > > > > ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the
> > > > > > > > > > > rate
> > > > > > > > > > > of
> > > > > > > > > >
> > > > > > > > > > > the crashing... but the ripple itself wasn't causing crashing.
> > > > > > > > > > > Adding (non-specific size) ferrites to the pump wires, and 120VAC
> > > > > > > > > > > input
> > > > > > > > > > > wires
> > > > > > > > > >
> > > > > > > > > > > did not help.
> > > > > > > > > > > I then tried to create a crude/uncalculated LC filter (which
> > > > > > > > > > > whatever
> > > > > > > > > > > components I had on hand (33uh inductor and 1000uf capacitor,
> > > > > > > > > > > should
> > > > > > > > > > > be
> > > > > > >
> > > > > > > > > > > low ESR), then a Pi filter (added 680 uF capacitor), and those
> > > > > > > > > > > barely
> > > > > > > > > > > made
> > > > > > > > >
> > > > > > > > > > a
> > > > > > > > > >
> > > > > > > > > > > dent.
> > > > > > > > > > > Eventually I added another 0.1uf capacitor to the output side of
> > > > > > > > > > > the
> > > > > > > > > > > pi
> > > > > > >
> > > > > > > > > > filter
> > > > > > > > > >
> > > > > > > > > > > and that helped enough to prevent the microcontroller crashing.
> > > > > > > > > > > But there is still a lot of noise on the 3.3V line...
> > > > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
> > > > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
> > > > > > > > > > > FWIW, this is where it ended up...
> > > > > > > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
> > > > > > > > > > > The noise is in the 7Mhz to 30Mhz range (prob even higher).
> > > > > > > > > > > I feel like smaller, low-ESR ceramic caps should help, but I doubt
> > > > > > > > > > > it
> > > > > > > > > > > will
> > > > > > > > >
> > > > > > > > > > take
> > > > > > > > > >
> > > > > > > > > > > out most of the noise.
> > > > > > > > > > > What is the right type of filter to eliminate this noise?
> > > > > > > > > > > Cheers,
> > > > > > > > > > > -Neil.
> > > > > > > > > > >
> > > > > > > > > > > ------------------------------------------------------------------------------------------------
> > > > > > > > > > >
> > > > > > > > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > > > > > > > > View/change your membership options at
> > > > > > > > > > > http://mailman.mit.edu/mailman/listinfo/piclist
> > > > > > > > > > >
> > > > > > > > > > > --------------------------------------------------------------------------------------------------------------------------------------------------------
> > > > > > > > > > >
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> > > > > > > > > > > View/change your membership options at
> > > > > > > > > > > http://mailman.mit.edu/mailman/listinfo/piclist
> > > > > > > > > > > --
> > > > > > > > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
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> > > > > > > > > > > --
> > >
> > > Jason White
> > >
> > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > View/change your membership options at
> > > http://mailman.mit.edu/mailman/listinfo/piclist
>
> --
>
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Re: [EE] Eliminating external noise through PS

Bob Blick-5
In reply to this post by Neil
Hi Neil,

These are the type of current clamps that I have used to track down trouble:

https://www.solar-emc.com/RFI-EMI.html

Best regards, Bob

________________________________________
From: [hidden email] <[hidden email]> on behalf of Neil
Sent: Wednesday, December 30, 2020 4:27 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Eliminating external noise through PS

Hmmm... not a current clamp, but I probably have a current sensor. Only
thing is that it would most probably be a high range (few 10's of amps
at least).

I really need to research and get some better equipment one of these days.

Cheers,
-Neil.



On 12/29/2020 5:30 PM, Bob Blick wrote:
> Hi Neil,
>
> I've found that measuring current is quite often better than measuring voltage when seeking out noise problems. I can be less convenient to do but at least where wires enter and exit the board it can be quite useful. Do you have a current clamp you can attach to your scope?
>
> Cheerful regards, Bob

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Re: [EE] Eliminating external noise through PS

David VanHorn-2
In reply to this post by Neil
10k might be light.  Try 1k pullup, and 100nF to ground?

On Wed, Dec 30, 2020 at 5:26 PM Neil <[hidden email]> wrote:

> Interesting thought... 10k pullup to +3v3.
>
>
>
>
> On 12/29/2020 5:13 PM, David VanHorn wrote:
> > What's your reset circuit look like?   High enough impedances here can
> > cause these problems.
> >
> > On Tue, Dec 29, 2020, 11:22 AM Neil <[hidden email]> wrote:
> >
> >> Happy holidays everyone.
> >>
> >> Okay, I got back to this recently and have a bunch of updates:
> >>
> >> For the tl;dr 'ers... I've got a lot of noise out, the processor does
> >> not crash anymore, but 2 questions remain:
> >>
> >> - Should I have the AC-outlet ground wire, coming onto the PCB and used
> >> as a shield?
> >>
> >> - If I hold the AC wire with my hand, the noise (as seen on the
> >> oscilloscope) drops (noticeably).  Shielding the AC wire does not have
> >> the same effect, so what is happening here, and how can I use this to
> >> help reduce the noise even more?
> >>
> >>
> >> For the gory details, here's my summary of what I tried and found...
> >>
> >> For reference...
> >> http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
> >> noise is mostly in the few Mhz range and higher.
> >>
> >> - Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
> >> - Low-pass filter helped minimally
> >> - Pi filter was a bit better, but still small impact.
> >> - Common mode choke (uncalculated, but should've been able to separate
> >> 60Hz from Mhz-range noise) didn't help.  I am new to these, but
> >> apparently above some frequency the impedance drops again.
> >> - Ferrite across AC side of motor wires helped minimally.
> >> - Ferrite on incoming-power AC wires did not help
> >> - Removed relay (and jumper across contacts to run the pump) to see if
> >> noise was coming into board from that side, but nope.
> >> - Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
> >> with wires soldered on for the incoming power and parallel wires to run
> >> the pump, and a 1k load resistor on the PS output. Still a lot of noise
> >> - Low-pass filter again helped reduce noise minimally.
> >> - Capacitance multiplier helped noticeably.
> >> - 2 more ceramic caps from each motor wire to ground/motor case (right
> >> at the motor) helped noticeably.
> >> - Twisted the AC wires to the motor tighter, and didn't really see any
> >> difference.
> >> - Back to original board, to use some of these, but too much voltage
> >> drop on capacitance multiplier to be usable.  I should calculate this
> >> properly and find the right transistor for this.
> >>
> >> At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
> >> filter and the board isn't crashing, but I can still see some noise on
> >> the scope, which I'd like to reduce even more.  Going to try a
> >> multi-stage pi/LC filter.
> >>
> >> But I'm curious how to use the "phenomenon" where holding the AC wire in
> >> my hand reduces noise noticeably, to help this.
> >>
> >>
> >> Thanks,
> >> -Neil.
> >>
> >>
> >>
> >> On 12/13/2020 7:15 PM, Neil wrote:
> >>> That's a definite possibility at this point.  The original circuit
> >>> (prior version) worked great with 2 layers, but I needed 2oz copper to
> >>> handle the pump current.
> >>> Never version works just as great.  Or  I should say "worked", until
> >>> they decided to switch from the AC pump to this DC pump.
> >>>
> >>> Cheers,
> >>> -Neil
> >>>
> >>>
> >>>
> >>> On 12/13/2020 6:58 PM, Jason White wrote:
> >>>> Neil, from the pictures it looks like you're using a 2 layer PCB. Have
> >> you
> >>>> considered a 4 layer PCB? A continuous dedicated ground plane layer
> >> would
> >>>> drastically reduce the loop area (and thus susceptibility to EMI) of
> >> your
> >>>> traces.
> >>>>
> >>>> Otherwise, it may be worth considering moving the relays to a separate
> >>>> board/area.
> >>>>
> >>>> On Sunday, December 13, 2020, Neil <[hidden email]> wrote:
> >>>>
> >>>>> I strongly feel so, because in my early tests, I:
> >>>>> (a) disconnected one of the pump wires (so the pump wouldn't run),
> and
> >>>>> it was (expectedly) very clean (on the scope).
> >>>>> (b) disconnected both of the pump wires and plugged it into the
> female
> >>>>> side of a PC power cord, so the pump ran, but was connected to 120VAC
> >>>>> from a different source.  Very clean power again.
> >>>>> In both cases, all else stayed the same including where the wires
> were
> >>>>> draped, etc.
> >>>>>
> >>>>> In other tests, I moved the scope, power lines, etc and no change to
> >> the
> >>>>> noise on the line.
> >>>>>
> >>>>> Either way, I haven't done my other tests yet since I took the pump
> >> with
> >>>>> me, so I'll get to those this week.
> >>>>>
> >>>>> Cheers,
> >>>>> -Neil.
> >>>>>
> >>>>>
> >>>>> On 12/11/2020 7:37 PM, Jason White wrote:
> >>>>>> Hi Neil,
> >>>>>>
> >>>>>> This may be a silly question: are you sure that some of these
> voltage
> >>>>>> spikes that you've captured on the scope are not artifacts of your
> >>>>>> measurement setup? The loop formed by the ground wire/clip on a
> scope
> >>>>> probe
> >>>>>> makes a very effective antenna. Maybe your power rail is cleaner
> than
> >> you
> >>>>>> think - in which case the true problem might be elsewhere.
> >>>>>>
> >>>>>> -Jason White
> >>>>>>
> >>>>>> On Fri, Dec 11, 2020 at 3:11 PM Neil <[hidden email]> wrote:
> >>>>>>
> >>>>>>> Sorry, disappeared for a couple days, but some quick answers to
> >>>>>>> everything for now, and my next steps:
> >>>>>>>
> >>>>>>> - Yes I have flyback diodes.   Highlighted with yellow here,  just
> >> above
> >>>>>>> the relays...
> >>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
> >>>>>>> - James & Russell, in that diagram also, I labeled the paths for
> >> power.
> >>>>>>> The 5V to the relays is pretty much dedicated and 5V is on the top
> >>>>>>> layer, and (dedicated) ground for the relays on the bottom layer.
> >> But
> >>>>>>> yes, it's right up against the AC section, but as many components
> >> have
> >>>>>>> been removed now, I will push that far away.
> >>>>>>> - The 3.3V regulator has been getting a bit warmer than I like, so
> I
> >>>>>>> have been planning to use a buck converter instead.  But maybe I
> >> should
> >>>>>>> run two 3.3V regulators instead?  I would think that the buck
> >> converter
> >>>>>>> would be pass less of the noise through.
> >>>>>>> - I ran over there quickly to pick up stuff and tried a crude
> >>>>>>> (uncalculated) common-mode choke I made up from stuff I could find.
> >> Did
> >>>>>>> not make in dent in the noise coming through.
> >>>>>>> See here...
> >>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
> >>>>>>> - I feel like Brent may be correct, that the noise may be coming
> from
> >>>>>>> the relay side.  The processor (ESP32) is resetting.  I know it's
> >> not a
> >>>>>>> firmware issue as it had zero crashes with the previous pump.
> >>>>>>>
> >>>>>>>
> >>>>>>> Adding some info:
> >>>>>>> The previous pump was a huge AC pump.  This new pump is actually
> DC,
> >> but
> >>>>>>> there's a bridge rectifier on the wires.  So I'm now convinced that
> >> the
> >>>>>>> noise is coming from brushes.
> >>>>>>> I brought the pump with me, and I have a new blank board.  My plan
> >> is to
> >>>>>>> reproduce just enough of the circuit to see the noise, and I can
> cut
> >> and
> >>>>>>> re-route traces (the 5V & ground to the relays) to see if helps.
> >>>>>>> I will also add a ceramic capacitor to the pump wires (right at the
> >>>>>>> pump), and hope that helps.  Plus twist the wires.
> >>>>>>>
> >>>>>>> I'll be back with some results.
> >>>>>>>
> >>>>>>> Cheers,
> >>>>>>> -Neil.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> On 12/10/2020 7:28 PM, FTL wrote:
> >>>>>>>> This is almost too obvious, but in the schematic I do not see a
> >> flyback
> >>>>>>>> diode across the relay to suppress the back EMF when the relay is
> >>>>> turned
> >>>>>>>> off. The lack of diode would cause a serious spike in the 5V
> supply
> >>>>> when
> >>>>>>> the
> >>>>>>>> relay is turned off.
> >>>>>>>>
> >>>>>>>> Is the transistor being turned on hard enough to keep the relay on
> >>>>>>> properly.
> >>>>>>>> If it is not fully on with no flyback diode, maybe it is
> >> occasionally
> >>>>>>>> releasing and causing big noise on the 5V bus.
> >>>>>>>>
> >>>>>>>>> -----Original Message-----
> >>>>>>>>> From: [hidden email] <[hidden email]> On
> Behalf
> >> Of
> >>>>>>> Neil
> >>>>>>>>> Sent: December 8, 2020 11:04 AM
> >>>>>>>>> To: Microcontroller discussion list - Public. <[hidden email]>
> >>>>>>>>> Subject: [EE] Eliminating external noise through PS
> >>>>>>>>>
> >>>>>>>>> Hi,
> >>>>>>>>>
> >>>>>>>>> I'm working on a device that takes 120VAC, converts to 5VDC with
> a
> >>>>> PCB-
> >>>>>>>>> mounted power supply, then further reduces that to 3.3VDC with a
> >>>>> linear
> >>>>>>>>> regulator.
> >>>>>>>>> A 3.3V microcontroller switches a relay to power a 120VAC pump.
> >>>>>>>>> Overview...
> >>>>>>>>>
> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
> >>>>>>>>>
> >>>>>>>>> All has been great until we switched to a specific pump, which
> >> happens
> >>>>>>> to
> >>>>>>>>> generate a LOT of conducted noise, which passes through the 5V
> PS,
> >> and
> >>>>>>> the
> >>>>>>>>> 3.3V regulator, and causing the microcontroller to crash.
> >>>>>>>>> I did a bunch of tested and found that the noise is being
> conducted
> >>>>>>>> through
> >>>>>>>>> the wires back to the board through the PS, through the linear
> >>>>>>> regulator,
> >>>>>>>> and
> >>>>>>>>> this is the 3.3V line...
> >>>>>>>>>
> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
> >>>>>>>>>
> >>>>>>>>> I was over at someone else's place so did not have a lot of parts
> >> with
> >>>>>>> me,
> >>>>>>>>> but...
> >>>>>>>>> Adding a bunch more 0.1uf bypass capacitors all over the board
> did
> >> not
> >>>>>>>> help.
> >>>>>>>>> Changing the power supply from an IRM-10-5 (industrial spec,
> 200mV
> >>>>>>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce
> the
> >>>>> rate
> >>>>>>>> of
> >>>>>>>>> the crashing... but the ripple itself wasn't causing crashing.
> >>>>>>>>>
> >>>>>>>>> Adding (non-specific size) ferrites to the pump wires, and 120VAC
> >>>>> input
> >>>>>>>> wires
> >>>>>>>>> did not help.
> >>>>>>>>> I then tried to create a crude/uncalculated LC filter (which
> >> whatever
> >>>>>>>>> components I had on hand (33uh inductor and 1000uf capacitor,
> >> should
> >>>>> be
> >>>>>>>>> low ESR), then a Pi filter (added 680 uF capacitor), and those
> >> barely
> >>>>>>> made
> >>>>>>>> a
> >>>>>>>>> dent.
> >>>>>>>>> Eventually I added another 0.1uf capacitor to the output side of
> >> the
> >>>>> pi
> >>>>>>>> filter
> >>>>>>>>> and that helped enough to prevent the microcontroller crashing.
> >>>>>>>>> But there is still a lot of noise on the 3.3V line...
> >>>>>>>>>
> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
> >>>>>>>>>
> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
> >>>>>>>>>
> >>>>>>>>> FWIW, this is where it ended up...
> >>>>>>>>>
> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
> >>>>>>>>>
> >>>>>>>>> The noise is in the 7Mhz to 30Mhz range (prob even higher).
> >>>>>>>>> I feel like smaller, low-ESR ceramic caps should help, but I
> doubt
> >> it
> >>>>>>> will
> >>>>>>>> take
> >>>>>>>>> out most of the noise.
> >>>>>>>>> What is the right type of filter to eliminate this noise?
> >>>>>>>>>
> >>>>>>>>> Cheers,
> >>>>>>>>> -Neil.
> >>>>>>>>>
> >>>>>>>>> --
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> >>>>>>>
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Re: [EE] Eliminating external noise through PS

Richard Prosser
In reply to this post by madscientistatlarge
Or power the 'scope from a UPS with the mains disconnected?
RP

On Thu, 31 Dec 2020 at 14:17, madscientistatlarge <
[hidden email]> wrote:

> No, I meant using what in America, is a "grounding adapter", meant to
> convert 2 wire to 3 wire grounded outlets but useful for breaking ground
> loops if you don't connect the ground wire.  Of course this defeats a
> safety feature and should be done with care.  Basic idea is to not ground
> the scope through the power plug but rather through the probes connection.
>
>
> Sent with ProtonMail Secure Email.
>
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Wednesday, December 30, 2020 5:22 PM, Neil <[hidden email]>
> wrote:
>
> > Just mentioned that in another post (Grounded with regular lead/clip,
> > but prev tried paperclip mod and didn't see a change then so went back
> > to regular lead/clip), so will try it again. Would be great if this was
> > the last bit of the issue.
> >
> > By "float the scope", do you mean using a transformer of some sort to
> > isolate the ground?
> >
> > Shielding the AC wires didn't make much of a dent... I first tried
> > aluminum foil and grounded on the motor side. Then I tried actual
> > shielding braid, but that didn't do anything either.
> >
> > I need to search for those packaged power entry filters.
> >
> > Cheers,
> > -Neil.
> >
> > On 12/29/2020 3:34 PM, madscientistatlarge wrote:
> >
> > > When you measure with the scope, how are you grounding the Probe?
> Those convenient wires with alligator clips make good antennas, best to
> take a wire, preferably beryllium copper because it's springy, and wrap one
> end around the exposed ground just behind the tip, then bend it to point
> the same way as the signal probe and trim to length so you are grounding it
> right where you are measuring. Might also want to float the scope to avoid
> ground loops. If you are in the U.S. These guys will sell a single foot of
> beryllium copper wire,
> http://lfa-wire.com/Plated-Wire-article/Plated-Wire-2.html. Haven't dealt
> with them but plan to as soon as I get my bench setup. I learned this trick
> on a job and have seen it mentioned once online (been online since 2000).
> In a pinch a piece of copper might work briefly, or any other stiff wire,
> possibly even a paper clip in a pinch (haven't tried it, steel does have
> some resistance but likely not too bad on 1cm or less). When you cut the
> wire you can cut a nice point on the end.
> > > Noise will drive one batty, I once traced it to a leaky transformer in
> a flow controller. The current was going to ground through the computer's
> data acq card and sporadically making noise on the measurement. No
> permanent effect in that case. Thing was when I connected the scope ground
> to the equipment it took the leakage and the noise went away, only saw it
> because I reasoned the scope was doing the magic. Opened the flow
> controller case and out of 4 transformers (1 for each channel) one had a
> big bubble on the encapsulation, I've always assumed it was spike damage.
> Replaced the transformer and away went the noise. The annoying thing is it
> had been in to the manufacturer for the noise problem and of course they
> found no issues (I don't blame them, I spent a day and a half playing with
> it before I figured it out).
> > > When you grab the lead and the noise drops you're probably being a
> lossy load, or getting phase cancellation, or??? In a pinch you could use
> shielded wiring to the motor, conduit might help enough, preferably
> grounded at only the motor (noise source) end of the line. Also unless
> your' filters are shielded, and the line to/from them noise can easily
> couple around the filter. This happens with power entry filtering if the
> wires run near each other, which makes the packaged power entry filters
> worth the extra $$ in many cases.
> > > Sent with ProtonMail Secure Email.
> > > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> > > On Tuesday, December 29, 2020 12:36 PM, Jason White
> [hidden email] wrote:
> > >
> > > > My experience developing "all discrete" (no microcontroller) motor
> driver
> > > > PCBs is that any noise that is unaffected by filtering tends to be a
> > > > measurement or environmental artifact.
> > > > I'd recommend doubled checking your probe/scope grounding - it is an
> > > > endless source of trouble and erroneous readings. I've found that
> often
> > > > times problems in systems are a result of a combination of "innocent
> > > > looking" and unrelated things that end up interacting in unexpected
> ways.
> > > > On Tuesday, December 29, 2020, Neil [hidden email] wrote:
> > > >
> > > > > Happy holidays everyone.
> > > > > Okay, I got back to this recently and have a bunch of updates:
> > > > > For the tl;dr 'ers... I've got a lot of noise out, the processor
> does
> > > > > not crash anymore, but 2 questions remain:
> >
> > > > > -   Should I have the AC-outlet ground wire, coming onto the PCB
> and used
> > > > >     as a shield?
> > > > >
> > > > > -   If I hold the AC wire with my hand, the noise (as seen on the
> > > > >     oscilloscope) drops (noticeably). Shielding the AC wire does
> not have
> > > > >     the same effect, so what is happening here, and how can I use
> this to
> > > > >     help reduce the noise even more?
> > > > >
> > > > >
> > > > > For the gory details, here's my summary of what I tried and
> found...
> > > > > For reference...
> > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg
> , and
> > > > > noise is mostly in the few Mhz range and higher.
> > > > >
> > > > > -   Ceramic cap across (DC) motor wires (right at the motor)
> helped a bit.
> > > > >
> > > > > -   Low-pass filter helped minimally
> > > > >
> > > > > -   Pi filter was a bit better, but still small impact.
> > > > >
> > > > > -   Common mode choke (uncalculated, but should've been able to
> separate
> > > > >     60Hz from Mhz-range noise) didn't help. I am new to these, but
> > > > >     apparently above some frequency the impedance drops again.
> > > > >
> > > > > -   Ferrite across AC side of motor wires helped minimally.
> > > > >
> > > > > -   Ferrite on incoming-power AC wires did not help
> > > > >
> > > > > -   Removed relay (and jumper across contacts to run the pump) to
> see if
> > > > >     noise was coming into board from that side, but nope.
> > > > >
> > > > > -   Started from scratch with a minimal setup -- the AC-DC PS (no
> PCB),
> > > > >     with wires soldered on for the incoming power and parallel
> wires to run
> > > > >     the pump, and a 1k load resistor on the PS output. Still a lot
> of noise
> > > > >
> > > > > -   Low-pass filter again helped reduce noise minimally.
> > > > >
> > > > > -   Capacitance multiplier helped noticeably.
> > > > >
> > > > > -   2 more ceramic caps from each motor wire to ground/motor case
> (right
> > > > >     at the motor) helped noticeably.
> > > > >
> > > > > -   Twisted the AC wires to the motor tighter, and didn't really
> see any
> > > > >     difference.
> > > > >
> > > > > -   Back to original board, to use some of these, but too much
> voltage
> > > > >     drop on capacitance multiplier to be usable. I should
> calculate this
> > > > >     properly and find the right transistor for this.
> > > > >
> > > > >
> > > > > At this point, I have 3 @ 0.01uf ceramic caps at the motor and the
> pi
> > > > > filter and the board isn't crashing, but I can still see some
> noise on
> > > > > the scope, which I'd like to reduce even more. Going to try a
> > > > > multi-stage pi/LC filter.
> > > > > But I'm curious how to use the "phenomenon" where holding the AC
> wire in
> > > > > my hand reduces noise noticeably, to help this.
> > > > > Thanks,
> > > > > -Neil.
> > > > > On 12/13/2020 7:15 PM, Neil wrote:
> > > > >
> > > > > > That's a definite possibility at this point. The original circuit
> > > > > > (prior version) worked great with 2 layers, but I needed 2oz
> copper to
> > > > > > handle the pump current.
> > > > > > Never version works just as great. Or I should say "worked",
> until
> > > > > > they decided to switch from the AC pump to this DC pump.
> > > > > > Cheers,
> > > > > > -Neil
> > > > > > On 12/13/2020 6:58 PM, Jason White wrote:
> > > > > >
> > > > > > > Neil, from the pictures it looks like you're using a 2 layer
> PCB. Have
> > > > > > > you
> > > > > > > considered a 4 layer PCB? A continuous dedicated ground plane
> layer
> > > > > > > would
> > > > > > > drastically reduce the loop area (and thus susceptibility to
> EMI) of
> > > > > > > your
> > > > > > > traces.
> > > > > > > Otherwise, it may be worth considering moving the relays to a
> separate
> > > > > > > board/area.
> > > > > > > On Sunday, December 13, 2020, Neil [hidden email] wrote:
> > > > > > >
> > > > > > > > I strongly feel so, because in my early tests, I:
> > > > > > > > (a) disconnected one of the pump wires (so the pump wouldn't
> run), and
> > > > > > > > it was (expectedly) very clean (on the scope).
> > > > > > > > (b) disconnected both of the pump wires and plugged it into
> the female
> > > > > > > > side of a PC power cord, so the pump ran, but was connected
> to 120VAC
> > > > > > > > from a different source. Very clean power again.
> > > > > > > > In both cases, all else stayed the same including where the
> wires were
> > > > > > > > draped, etc.
> > > > > > > > In other tests, I moved the scope, power lines, etc and no
> change to
> > > > > > > > the
> > > > > > > > noise on the line.
> > > > > > > > Either way, I haven't done my other tests yet since I took
> the pump
> > > > > > > > with
> > > > > > > > me, so I'll get to those this week.
> > > > > > > > Cheers,
> > > > > > > > -Neil.
> > > > > > > > On 12/11/2020 7:37 PM, Jason White wrote:
> > > > > > > >
> > > > > > > > > Hi Neil,
> > > > > > > > > This may be a silly question: are you sure that some of
> these voltage
> > > > > > > > > spikes that you've captured on the scope are not artifacts
> of your
> > > > > > > > > measurement setup? The loop formed by the ground wire/clip
> on a scope
> > > > > > > > > probe
> > > > > > > > > makes a very effective antenna. Maybe your power rail is
> cleaner than
> > > > > > > > > you
> > > > > > > > > think - in which case the true problem might be elsewhere.
> > > > > > > > > -Jason White
> > > > > > > > > On Fri, Dec 11, 2020 at 3:11 PM Neil [hidden email]
> wrote:
> > > > > > > > >
> > > > > > > > > > Sorry, disappeared for a couple days, but some quick
> answers to
> > > > > > > > > > everything for now, and my next steps:
> > > > > > > > > >
> > > > > > > > > > -   Yes I have flyback diodes. Highlighted with yellow
> here, just
> > > > > > > > > >     above
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > the relays...
> > > > > > > > > >
> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
> > > > > > > > > >
> > > > > > > > > > -   James & Russell, in that diagram also, I labeled the
> paths for
> > > > > > > > > >     power.
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > The 5V to the relays is pretty much dedicated and 5V is
> on the top
> > > > > > > > > > layer, and (dedicated) ground for the relays on the
> bottom layer.
> > > > > > > > > > But
> > > > > > > > > > yes, it's right up against the AC section, but as many
> components
> > > > > > > > > > have
> > > > > > > > > > been removed now, I will push that far away.
> > > > > > > > > >
> > > > > > > > > > -   The 3.3V regulator has been getting a bit warmer
> than I like, so I
> > > > > > > > > >     have been planning to use a buck converter instead.
> But maybe I
> > > > > > > > > >     should
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > run two 3.3V regulators instead? I would think that the
> buck
> > > > > > > > > > converter
> > > > > > > > > > would be pass less of the noise through.
> > > > > > > > > >
> > > > > > > > > > -   I ran over there quickly to pick up stuff and tried
> a crude
> > > > > > > > > >     (uncalculated) common-mode choke I made up from
> stuff I could find.
> > > > > > > > > >     Did
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > not make in dent in the noise coming through.
> > > > > > > > > > See here...
> > > > > > > > > >
> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
> > > > > > > > > >
> > > > > > > > > > -   I feel like Brent may be correct, that the noise may
> be coming from
> > > > > > > > > >     the relay side. The processor (ESP32) is resetting.
> I know it's
> > > > > > > > > >     not a
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > firmware issue as it had zero crashes with the previous
> pump.
> > > > > > > > > > Adding some info:
> > > > > > > > > > The previous pump was a huge AC pump. This new pump is
> actually DC,
> > > > > > > > > > but
> > > > > > > > > > there's a bridge rectifier on the wires. So I'm now
> convinced that
> > > > > > > > > > the
> > > > > > > > > > noise is coming from brushes.
> > > > > > > > > > I brought the pump with me, and I have a new blank
> board. My plan
> > > > > > > > > > is to
> > > > > > > > > > reproduce just enough of the circuit to see the noise,
> and I can cut
> > > > > > > > > > and
> > > > > > > > > > re-route traces (the 5V & ground to the relays) to see
> if helps.
> > > > > > > > > > I will also add a ceramic capacitor to the pump wires
> (right at the
> > > > > > > > > > pump), and hope that helps. Plus twist the wires.
> > > > > > > > > > I'll be back with some results.
> > > > > > > > > > Cheers,
> > > > > > > > > > -Neil.
> > > > > > > > > > On 12/10/2020 7:28 PM, FTL wrote:
> > > > > > > > > >
> > > > > > > > > > > This is almost too obvious, but in the schematic I do
> not see a
> > > > > > > > > > > flyback
> > > > > > > > > > > diode across the relay to suppress the back EMF when
> the relay is
> > > > > > > > > > > turned
> > > > > > > > > > > off. The lack of diode would cause a serious spike in
> the 5V supply
> > > > > > > > > > > when
> > > > > > > > > > > the
> > > > > > > > > >
> > > > > > > > > > > relay is turned off.
> > > > > > > > > > > Is the transistor being turned on hard enough to keep
> the relay on
> > > > > > > > > > > properly.
> > > > > > > > > > > If it is not fully on with no flyback diode, maybe it
> is
> > > > > > > > > > > occasionally
> > > > > > > > > > > releasing and causing big noise on the 5V bus.
> > > > > > > > > > >
> > > > > > > > > > > > -----Original Message-----
> > > > > > > > > > > > From: [hidden email]
> [hidden email] On Behalf
> > > > > > > > > > > > Of
> > > > > > > > > > > > Neil
> > > > > > > > > >
> > > > > > > > > > > > Sent: December 8, 2020 11:04 AM
> > > > > > > > > > > > To: Microcontroller discussion list - Public.
> [hidden email]
> > > > > > > > > > > > Subject: [EE] Eliminating external noise through PS
> > > > > > > > > > > > Hi,
> > > > > > > > > > > > I'm working on a device that takes 120VAC, converts
> to 5VDC with a
> > > > > > > > > > > > PCB-
> > > > > > > > > > > > mounted power supply, then further reduces that to
> 3.3VDC with a
> > > > > > > > > > > > linear
> > > > > > > > > > > > regulator.
> > > > > > > > > > > > A 3.3V microcontroller switches a relay to power a
> 120VAC pump.
> > > > > > > > > > > > Overview...
> > > > > > > > > > > >
> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
> > > > > > > > > > > > All has been great until we switched to a specific
> pump, which
> > > > > > > > > > > > happens
> > > > > > > > > > > > to
> > > > > > > > > >
> > > > > > > > > > > > generate a LOT of conducted noise, which passes
> through the 5V PS,
> > > > > > > > > > > > and
> > > > > > > > > > > > the
> > > > > > > > > >
> > > > > > > > > > > > 3.3V regulator, and causing the microcontroller to
> crash.
> > > > > > > > > > > > I did a bunch of tested and found that the noise is
> being conducted
> > > > > > > > > > > > through
> > > > > > > > > > > > the wires back to the board through the PS, through
> the linear
> > > > > > > > > > > > regulator,
> > > > > > > > > > > > and
> > > > > > > > > > > > this is the 3.3V line...
> > > > > > > > > > > >
> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
> > > > > > > > > > > > I was over at someone else's place so did not have a
> lot of parts
> > > > > > > > > > > > with
> > > > > > > > > > > > me,
> > > > > > > > > >
> > > > > > > > > > > > but...
> > > > > > > > > > > > Adding a bunch more 0.1uf bypass capacitors all over
> the board did
> > > > > > > > > > > > not
> > > > > > > > > > > > help.
> > > > > > > > > > >
> > > > > > > > > > > > Changing the power supply from an IRM-10-5
> (industrial spec, 200mV
> > > > > > > > > > > > ripple) to MPM-10-5 (medical spec, 100mV ripple),
> helped reduce the
> > > > > > > > > > > > rate
> > > > > > > > > > > > of
> > > > > > > > > > >
> > > > > > > > > > > > the crashing... but the ripple itself wasn't causing
> crashing.
> > > > > > > > > > > > Adding (non-specific size) ferrites to the pump
> wires, and 120VAC
> > > > > > > > > > > > input
> > > > > > > > > > > > wires
> > > > > > > > > > >
> > > > > > > > > > > > did not help.
> > > > > > > > > > > > I then tried to create a crude/uncalculated LC
> filter (which
> > > > > > > > > > > > whatever
> > > > > > > > > > > > components I had on hand (33uh inductor and 1000uf
> capacitor,
> > > > > > > > > > > > should
> > > > > > > > > > > > be
> > > > > > > >
> > > > > > > > > > > > low ESR), then a Pi filter (added 680 uF capacitor),
> and those
> > > > > > > > > > > > barely
> > > > > > > > > > > > made
> > > > > > > > > >
> > > > > > > > > > > a
> > > > > > > > > > >
> > > > > > > > > > > > dent.
> > > > > > > > > > > > Eventually I added another 0.1uf capacitor to the
> output side of
> > > > > > > > > > > > the
> > > > > > > > > > > > pi
> > > > > > > >
> > > > > > > > > > > filter
> > > > > > > > > > >
> > > > > > > > > > > > and that helped enough to prevent the
> microcontroller crashing.
> > > > > > > > > > > > But there is still a lot of noise on the 3.3V line...
> > > > > > > > > > > >
> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
> > > > > > > > > > > >
> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
> > > > > > > > > > > > FWIW, this is where it ended up...
> > > > > > > > > > > >
> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
> > > > > > > > > > > > The noise is in the 7Mhz to 30Mhz range (prob even
> higher).
> > > > > > > > > > > > I feel like smaller, low-ESR ceramic caps should
> help, but I doubt
> > > > > > > > > > > > it
> > > > > > > > > > > > will
> > > > > > > > > >
> > > > > > > > > > > take
> > > > > > > > > > >
> > > > > > > > > > > > out most of the noise.
> > > > > > > > > > > > What is the right type of filter to eliminate this
> noise?
> > > > > > > > > > > > Cheers,
> > > > > > > > > > > > -Neil.
> > > > > > > > > > > >
> > > > > > > > > > > >
> ------------------------------------------------------------------------------------------------
> > > > > > > > > > > >
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> > > > > > > > > > > >
> > > > > > > > > > > >
> --------------------------------------------------------------------------------------------------------------------------------------------------------
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> > > > Jason White
> > > >
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Re: [EE] Eliminating external noise through PS

madscientistatlarge
That should work, depending on how quick you are and how long the UPS will last (could be rather stressful for a long session, with having to let it recharge and all, unless of course you have a huge battery or light load).  Probably the best isolation you could get, though an isolation transformer isn't bad, particularly at high frequency where the core is lossy.


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‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Thursday, December 31, 2020 1:33 AM, Richard Prosser <[hidden email]> wrote:

> Or power the 'scope from a UPS with the mains disconnected?
> RP
>
> On Thu, 31 Dec 2020 at 14:17, madscientistatlarge <
> [hidden email]> wrote:
>
> > No, I meant using what in America, is a "grounding adapter", meant to
> > convert 2 wire to 3 wire grounded outlets but useful for breaking ground
> > loops if you don't connect the ground wire. Of course this defeats a
> > safety feature and should be done with care. Basic idea is to not ground
> > the scope through the power plug but rather through the probes connection.
> > Sent with ProtonMail Secure Email.
> > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> > On Wednesday, December 30, 2020 5:22 PM, Neil [hidden email]
> > wrote:
> >
> > > Just mentioned that in another post (Grounded with regular lead/clip,
> > > but prev tried paperclip mod and didn't see a change then so went back
> > > to regular lead/clip), so will try it again. Would be great if this was
> > > the last bit of the issue.
> > > By "float the scope", do you mean using a transformer of some sort to
> > > isolate the ground?
> > > Shielding the AC wires didn't make much of a dent... I first tried
> > > aluminum foil and grounded on the motor side. Then I tried actual
> > > shielding braid, but that didn't do anything either.
> > > I need to search for those packaged power entry filters.
> > > Cheers,
> > > -Neil.
> > > On 12/29/2020 3:34 PM, madscientistatlarge wrote:
> > >
> > > > When you measure with the scope, how are you grounding the Probe?
> > > > Those convenient wires with alligator clips make good antennas, best to
> > > > take a wire, preferably beryllium copper because it's springy, and wrap one
> > > > end around the exposed ground just behind the tip, then bend it to point
> > > > the same way as the signal probe and trim to length so you are grounding it
> > > > right where you are measuring. Might also want to float the scope to avoid
> > > > ground loops. If you are in the U.S. These guys will sell a single foot of
> > > > beryllium copper wire,
> > > > http://lfa-wire.com/Plated-Wire-article/Plated-Wire-2.html. Haven't dealt
> > > > with them but plan to as soon as I get my bench setup. I learned this trick
> > > > on a job and have seen it mentioned once online (been online since 2000).
> > > > In a pinch a piece of copper might work briefly, or any other stiff wire,
> > > > possibly even a paper clip in a pinch (haven't tried it, steel does have
> > > > some resistance but likely not too bad on 1cm or less). When you cut the
> > > > wire you can cut a nice point on the end.
> > >
> > > > Noise will drive one batty, I once traced it to a leaky transformer in
> > > > a flow controller. The current was going to ground through the computer's
> > > > data acq card and sporadically making noise on the measurement. No
> > > > permanent effect in that case. Thing was when I connected the scope ground
> > > > to the equipment it took the leakage and the noise went away, only saw it
> > > > because I reasoned the scope was doing the magic. Opened the flow
> > > > controller case and out of 4 transformers (1 for each channel) one had a
> > > > big bubble on the encapsulation, I've always assumed it was spike damage.
> > > > Replaced the transformer and away went the noise. The annoying thing is it
> > > > had been in to the manufacturer for the noise problem and of course they
> > > > found no issues (I don't blame them, I spent a day and a half playing with
> > > > it before I figured it out).
> > >
> > > > When you grab the lead and the noise drops you're probably being a
> > > > lossy load, or getting phase cancellation, or??? In a pinch you could use
> > > > shielded wiring to the motor, conduit might help enough, preferably
> > > > grounded at only the motor (noise source) end of the line. Also unless
> > > > your' filters are shielded, and the line to/from them noise can easily
> > > > couple around the filter. This happens with power entry filtering if the
> > > > wires run near each other, which makes the packaged power entry filters
> > > > worth the extra $$ in many cases.
> > >
> > > > Sent with ProtonMail Secure Email.
> > > > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> > > > On Tuesday, December 29, 2020 12:36 PM, Jason White
> > > > [hidden email] wrote:
> > >
> > > > > My experience developing "all discrete" (no microcontroller) motor
> > > > > driver
> > >
> > > > > PCBs is that any noise that is unaffected by filtering tends to be a
> > > > > measurement or environmental artifact.
> > > > > I'd recommend doubled checking your probe/scope grounding - it is an
> > > > > endless source of trouble and erroneous readings. I've found that
> > > > > often
> > >
> > > > > times problems in systems are a result of a combination of "innocent
> > > > > looking" and unrelated things that end up interacting in unexpected
> > > > > ways.
> > >
> > > > > On Tuesday, December 29, 2020, Neil [hidden email] wrote:
> > > > >
> > > > > > Happy holidays everyone.
> > > > > > Okay, I got back to this recently and have a bunch of updates:
> > > > > > For the tl;dr 'ers... I've got a lot of noise out, the processor
> > > > > > does
> > >
> > > > > > not crash anymore, but 2 questions remain:
> > >
> > > > > > -   Should I have the AC-outlet ground wire, coming onto the PCB
> > > > > >     and used
> > > > > >
> > >
> > > > > >     as a shield?
> > > > > >
> > > > > >
> > > > > > -   If I hold the AC wire with my hand, the noise (as seen on the
> > > > > >     oscilloscope) drops (noticeably). Shielding the AC wire does
> > > > > >     not have
> > > > > >
> > >
> > > > > >     the same effect, so what is happening here, and how can I use
> > > > > >
> >
> > this to
> >
> > > > > >     help reduce the noise even more?
> > > > > >
> > > > > >
> > > > > > For the gory details, here's my summary of what I tried and
> > > > > > found...
> > >
> > > > > > For reference...
> > > > > > http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg
> > > > > > , and
> > >
> > > > > > noise is mostly in the few Mhz range and higher.
> > > > > >
> > > > > > -   Ceramic cap across (DC) motor wires (right at the motor)
> > > > > >     helped a bit.
> > > > > >
> > >
> > > > > > -   Low-pass filter helped minimally
> > > > > >
> > > > > > -   Pi filter was a bit better, but still small impact.
> > > > > >
> > > > > > -   Common mode choke (uncalculated, but should've been able to
> > > > > >     separate
> > > > > >
> > >
> > > > > >     60Hz from Mhz-range noise) didn't help. I am new to these, but
> > > > > >     apparently above some frequency the impedance drops again.
> > > > > >
> > > > > >
> > > > > > -   Ferrite across AC side of motor wires helped minimally.
> > > > > >
> > > > > > -   Ferrite on incoming-power AC wires did not help
> > > > > >
> > > > > > -   Removed relay (and jumper across contacts to run the pump) to
> > > > > >     see if
> > > > > >
> > >
> > > > > >     noise was coming into board from that side, but nope.
> > > > > >
> > > > > >
> > > > > > -   Started from scratch with a minimal setup -- the AC-DC PS (no
> > > > > >     PCB),
> > > > > >
> > >
> > > > > >     with wires soldered on for the incoming power and parallel
> > > > > >
> >
> > wires to run
> >
> > > > > >     the pump, and a 1k load resistor on the PS output. Still a lot
> > > > > >
> >
> > of noise
> >
> > > > > > -   Low-pass filter again helped reduce noise minimally.
> > > > > >
> > > > > > -   Capacitance multiplier helped noticeably.
> > > > > >
> > > > > > -   2 more ceramic caps from each motor wire to ground/motor case
> > > > > >     (right
> > > > > >
> > >
> > > > > >     at the motor) helped noticeably.
> > > > > >
> > > > > >
> > > > > > -   Twisted the AC wires to the motor tighter, and didn't really
> > > > > >     see any
> > > > > >
> > >
> > > > > >     difference.
> > > > > >
> > > > > >
> > > > > > -   Back to original board, to use some of these, but too much
> > > > > >     voltage
> > > > > >
> > >
> > > > > >     drop on capacitance multiplier to be usable. I should
> > > > > >
> >
> > calculate this
> >
> > > > > >     properly and find the right transistor for this.
> > > > > >
> > > > > >
> > > > > > At this point, I have 3 @ 0.01uf ceramic caps at the motor and the
> > > > > > pi
> > >
> > > > > > filter and the board isn't crashing, but I can still see some
> > > > > > noise on
> > >
> > > > > > the scope, which I'd like to reduce even more. Going to try a
> > > > > > multi-stage pi/LC filter.
> > > > > > But I'm curious how to use the "phenomenon" where holding the AC
> > > > > > wire in
> > >
> > > > > > my hand reduces noise noticeably, to help this.
> > > > > > Thanks,
> > > > > > -Neil.
> > > > > > On 12/13/2020 7:15 PM, Neil wrote:
> > > > > >
> > > > > > > That's a definite possibility at this point. The original circuit
> > > > > > > (prior version) worked great with 2 layers, but I needed 2oz
> > > > > > > copper to
> > >
> > > > > > > handle the pump current.
> > > > > > > Never version works just as great. Or I should say "worked",
> > > > > > > until
> > >
> > > > > > > they decided to switch from the AC pump to this DC pump.
> > > > > > > Cheers,
> > > > > > > -Neil
> > > > > > > On 12/13/2020 6:58 PM, Jason White wrote:
> > > > > > >
> > > > > > > > Neil, from the pictures it looks like you're using a 2 layer
> > > > > > > > PCB. Have
> > >
> > > > > > > > you
> > > > > > > > considered a 4 layer PCB? A continuous dedicated ground plane
> > > > > > > > layer
> > >
> > > > > > > > would
> > > > > > > > drastically reduce the loop area (and thus susceptibility to
> > > > > > > > EMI) of
> > >
> > > > > > > > your
> > > > > > > > traces.
> > > > > > > > Otherwise, it may be worth considering moving the relays to a
> > > > > > > > separate
> > >
> > > > > > > > board/area.
> > > > > > > > On Sunday, December 13, 2020, Neil [hidden email] wrote:
> > > > > > > >
> > > > > > > > > I strongly feel so, because in my early tests, I:
> > > > > > > > > (a) disconnected one of the pump wires (so the pump wouldn't
> > > > > > > > > run), and
> > >
> > > > > > > > > it was (expectedly) very clean (on the scope).
> > > > > > > > > (b) disconnected both of the pump wires and plugged it into
> > > > > > > > > the female
> > >
> > > > > > > > > side of a PC power cord, so the pump ran, but was connected
> > > > > > > > > to 120VAC
> > >
> > > > > > > > > from a different source. Very clean power again.
> > > > > > > > > In both cases, all else stayed the same including where the
> > > > > > > > > wires were
> > >
> > > > > > > > > draped, etc.
> > > > > > > > > In other tests, I moved the scope, power lines, etc and no
> > > > > > > > > change to
> > >
> > > > > > > > > the
> > > > > > > > > noise on the line.
> > > > > > > > > Either way, I haven't done my other tests yet since I took
> > > > > > > > > the pump
> > >
> > > > > > > > > with
> > > > > > > > > me, so I'll get to those this week.
> > > > > > > > > Cheers,
> > > > > > > > > -Neil.
> > > > > > > > > On 12/11/2020 7:37 PM, Jason White wrote:
> > > > > > > > >
> > > > > > > > > > Hi Neil,
> > > > > > > > > > This may be a silly question: are you sure that some of
> > > > > > > > > > these voltage
> > >
> > > > > > > > > > spikes that you've captured on the scope are not artifacts
> > > > > > > > > > of your
> > >
> > > > > > > > > > measurement setup? The loop formed by the ground wire/clip
> > > > > > > > > > on a scope
> > >
> > > > > > > > > > probe
> > > > > > > > > > makes a very effective antenna. Maybe your power rail is
> > > > > > > > > > cleaner than
> > >
> > > > > > > > > > you
> > > > > > > > > > think - in which case the true problem might be elsewhere.
> > > > > > > > > > -Jason White
> > > > > > > > > > On Fri, Dec 11, 2020 at 3:11 PM Neil [hidden email]
> > > > > > > > > > wrote:
> > >
> > > > > > > > > > > Sorry, disappeared for a couple days, but some quick
> > > > > > > > > > > answers to
> > >
> > > > > > > > > > > everything for now, and my next steps:
> > > > > > > > > > >
> > > > > > > > > > > -   Yes I have flyback diodes. Highlighted with yellow
> > > > > > > > > > >     here, just
> > > > > > > > > > >
> > >
> > > > > > > > > > >     above
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > the relays...
> >
> > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
> >
> > > > > > > > > > > -   James & Russell, in that diagram also, I labeled the
> > > > > > > > > > >     paths for
> > > > > > > > > > >
> > >
> > > > > > > > > > >     power.
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > The 5V to the relays is pretty much dedicated and 5V is
> > > > > > > > > > > on the top
> > >
> > > > > > > > > > > layer, and (dedicated) ground for the relays on the
> > > > > > > > > > > bottom layer.
> > >
> > > > > > > > > > > But
> > > > > > > > > > > yes, it's right up against the AC section, but as many
> > > > > > > > > > > components
> > >
> > > > > > > > > > > have
> > > > > > > > > > > been removed now, I will push that far away.
> > > > > > > > > > >
> > > > > > > > > > > -   The 3.3V regulator has been getting a bit warmer
> > > > > > > > > > >     than I like, so I
> > > > > > > > > > >
> > >
> > > > > > > > > > >     have been planning to use a buck converter instead.
> > > > > > > > > > >
> >
> > But maybe I
> >
> > > > > > > > > > >     should
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > run two 3.3V regulators instead? I would think that the
> > > > > > > > > > > buck
> > >
> > > > > > > > > > > converter
> > > > > > > > > > > would be pass less of the noise through.
> > > > > > > > > > >
> > > > > > > > > > > -   I ran over there quickly to pick up stuff and tried
> > > > > > > > > > >     a crude
> > > > > > > > > > >
> > >
> > > > > > > > > > >     (uncalculated) common-mode choke I made up from
> > > > > > > > > > >
> >
> > stuff I could find.
> >
> > > > > > > > > > >     Did
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > not make in dent in the noise coming through.
> > > > > > > > > > > See here...
> >
> > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
> >
> > > > > > > > > > > -   I feel like Brent may be correct, that the noise may
> > > > > > > > > > >     be coming from
> > > > > > > > > > >
> > >
> > > > > > > > > > >     the relay side. The processor (ESP32) is resetting.
> > > > > > > > > > >
> >
> > I know it's
> >
> > > > > > > > > > >     not a
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > firmware issue as it had zero crashes with the previous
> > > > > > > > > > > pump.
> > >
> > > > > > > > > > > Adding some info:
> > > > > > > > > > > The previous pump was a huge AC pump. This new pump is
> > > > > > > > > > > actually DC,
> > >
> > > > > > > > > > > but
> > > > > > > > > > > there's a bridge rectifier on the wires. So I'm now
> > > > > > > > > > > convinced that
> > >
> > > > > > > > > > > the
> > > > > > > > > > > noise is coming from brushes.
> > > > > > > > > > > I brought the pump with me, and I have a new blank
> > > > > > > > > > > board. My plan
> > >
> > > > > > > > > > > is to
> > > > > > > > > > > reproduce just enough of the circuit to see the noise,
> > > > > > > > > > > and I can cut
> > >
> > > > > > > > > > > and
> > > > > > > > > > > re-route traces (the 5V & ground to the relays) to see
> > > > > > > > > > > if helps.
> > >
> > > > > > > > > > > I will also add a ceramic capacitor to the pump wires
> > > > > > > > > > > (right at the
> > >
> > > > > > > > > > > pump), and hope that helps. Plus twist the wires.
> > > > > > > > > > > I'll be back with some results.
> > > > > > > > > > > Cheers,
> > > > > > > > > > > -Neil.
> > > > > > > > > > > On 12/10/2020 7:28 PM, FTL wrote:
> > > > > > > > > > >
> > > > > > > > > > > > This is almost too obvious, but in the schematic I do
> > > > > > > > > > > > not see a
> > >
> > > > > > > > > > > > flyback
> > > > > > > > > > > > diode across the relay to suppress the back EMF when
> > > > > > > > > > > > the relay is
> > >
> > > > > > > > > > > > turned
> > > > > > > > > > > > off. The lack of diode would cause a serious spike in
> > > > > > > > > > > > the 5V supply
> > >
> > > > > > > > > > > > when
> > > > > > > > > > > > the
> > > > > > > > > > >
> > > > > > > > > > > > relay is turned off.
> > > > > > > > > > > > Is the transistor being turned on hard enough to keep
> > > > > > > > > > > > the relay on
> > >
> > > > > > > > > > > > properly.
> > > > > > > > > > > > If it is not fully on with no flyback diode, maybe it
> > > > > > > > > > > > is
> > >
> > > > > > > > > > > > occasionally
> > > > > > > > > > > > releasing and causing big noise on the 5V bus.
> > > > > > > > > > > >
> > > > > > > > > > > > > -----Original Message-----
> > > > > > > > > > > > > From: [hidden email]
> > > > > > > > > > > > > [hidden email] On Behalf
> > >
> > > > > > > > > > > > > Of
> > > > > > > > > > > > > Neil
> > > > > > > > > > >
> > > > > > > > > > > > > Sent: December 8, 2020 11:04 AM
> > > > > > > > > > > > > To: Microcontroller discussion list - Public.
> > > > > > > > > > > > > [hidden email]
> > >
> > > > > > > > > > > > > Subject: [EE] Eliminating external noise through PS
> > > > > > > > > > > > > Hi,
> > > > > > > > > > > > > I'm working on a device that takes 120VAC, converts
> > > > > > > > > > > > > to 5VDC with a
> > >
> > > > > > > > > > > > > PCB-
> > > > > > > > > > > > > mounted power supply, then further reduces that to
> > > > > > > > > > > > > 3.3VDC with a
> > >
> > > > > > > > > > > > > linear
> > > > > > > > > > > > > regulator.
> > > > > > > > > > > > > A 3.3V microcontroller switches a relay to power a
> > > > > > > > > > > > > 120VAC pump.
> > >
> > > > > > > > > > > > > Overview...
> >
> > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
> >
> > > > > > > > > > > > > All has been great until we switched to a specific
> > > > > > > > > > > > > pump, which
> > >
> > > > > > > > > > > > > happens
> > > > > > > > > > > > > to
> > > > > > > > > > >
> > > > > > > > > > > > > generate a LOT of conducted noise, which passes
> > > > > > > > > > > > > through the 5V PS,
> > >
> > > > > > > > > > > > > and
> > > > > > > > > > > > > the
> > > > > > > > > > >
> > > > > > > > > > > > > 3.3V regulator, and causing the microcontroller to
> > > > > > > > > > > > > crash.
> > >
> > > > > > > > > > > > > I did a bunch of tested and found that the noise is
> > > > > > > > > > > > > being conducted
> > >
> > > > > > > > > > > > > through
> > > > > > > > > > > > > the wires back to the board through the PS, through
> > > > > > > > > > > > > the linear
> > >
> > > > > > > > > > > > > regulator,
> > > > > > > > > > > > > and
> > > > > > > > > > > > > this is the 3.3V line...
> >
> > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
> >
> > > > > > > > > > > > > I was over at someone else's place so did not have a
> > > > > > > > > > > > > lot of parts
> > >
> > > > > > > > > > > > > with
> > > > > > > > > > > > > me,
> > > > > > > > > > >
> > > > > > > > > > > > > but...
> > > > > > > > > > > > > Adding a bunch more 0.1uf bypass capacitors all over
> > > > > > > > > > > > > the board did
> > >
> > > > > > > > > > > > > not
> > > > > > > > > > > > > help.
> > > > > > > > > > > >
> > > > > > > > > > > > > Changing the power supply from an IRM-10-5
> > > > > > > > > > > > > (industrial spec, 200mV
> > >
> > > > > > > > > > > > > ripple) to MPM-10-5 (medical spec, 100mV ripple),
> > > > > > > > > > > > > helped reduce the
> > >
> > > > > > > > > > > > > rate
> > > > > > > > > > > > > of
> > > > > > > > > > > >
> > > > > > > > > > > > > the crashing... but the ripple itself wasn't causing
> > > > > > > > > > > > > crashing.
> > >
> > > > > > > > > > > > > Adding (non-specific size) ferrites to the pump
> > > > > > > > > > > > > wires, and 120VAC
> > >
> > > > > > > > > > > > > input
> > > > > > > > > > > > > wires
> > > > > > > > > > > >
> > > > > > > > > > > > > did not help.
> > > > > > > > > > > > > I then tried to create a crude/uncalculated LC
> > > > > > > > > > > > > filter (which
> > >
> > > > > > > > > > > > > whatever
> > > > > > > > > > > > > components I had on hand (33uh inductor and 1000uf
> > > > > > > > > > > > > capacitor,
> > >
> > > > > > > > > > > > > should
> > > > > > > > > > > > > be
> > > > > > > > >
> > > > > > > > > > > > > low ESR), then a Pi filter (added 680 uF capacitor),
> > > > > > > > > > > > > and those
> > >
> > > > > > > > > > > > > barely
> > > > > > > > > > > > > made
> > > > > > > > > > >
> > > > > > > > > > > > a
> > > > > > > > > > > >
> > > > > > > > > > > > > dent.
> > > > > > > > > > > > > Eventually I added another 0.1uf capacitor to the
> > > > > > > > > > > > > output side of
> > >
> > > > > > > > > > > > > the
> > > > > > > > > > > > > pi
> > > > > > > > >
> > > > > > > > > > > > filter
> > > > > > > > > > > >
> > > > > > > > > > > > > and that helped enough to prevent the
> > > > > > > > > > > > > microcontroller crashing.
> > >
> > > > > > > > > > > > > But there is still a lot of noise on the 3.3V line...
> >
> > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
> >
> > > > > > > > > > > > >
> >
> > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
> >
> > > > > > > > > > > > > FWIW, this is where it ended up...
> >
> > http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
> >
> > > > > > > > > > > > > The noise is in the 7Mhz to 30Mhz range (prob even
> > > > > > > > > > > > > higher).
> > >
> > > > > > > > > > > > > I feel like smaller, low-ESR ceramic caps should
> > > > > > > > > > > > > help, but I doubt
> > >
> > > > > > > > > > > > > it
> > > > > > > > > > > > > will
> > > > > > > > > > >
> > > > > > > > > > > > take
> > > > > > > > > > > >
> > > > > > > > > > > > > out most of the noise.
> > > > > > > > > > > > > What is the right type of filter to eliminate this
> > > > > > > > > > > > > noise?
> > >
> > > > > > > > > > > > > Cheers,
> > > > > > > > > > > > > -Neil.
> >
> > > > > > > > > > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ &
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> > >
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> >
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> > >
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> > > > > > > > > > > > > ---------------------------------------------------------------------------------------
> > > > > > > > > > > > >
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> > > > > > > > > > > > > ---------------------------------------------------------------------------------------
> > > > >
> > > > > Jason White
> > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> > > > > View/change your membership options at
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