I2C temperature sensors

[Charles Linquist]

Does anyone know of an I2C temperature sensor that either has a
programmable address, or has more than 3 address bits?

I need to hang 20 temperature sensors on one I2C bus, and I want
to make the hardware at the sensor end as simple as possible.


Charles Linquist



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[Robert Rolf]

Have you considered splitting the I2C bus into sections
using analog switches? Each downstream segment would
need it's own pullup resistors, but you could have
as many buses as you needed. Something like a 74HC4051
should work as an 8 channel switch if you only have
8 loads (sensors) per leg.

There was a PICLIST thread on 'multiple I2C buses' a
year or so ago, so there should be details in the archives.

If I remember correctly, you could common up the SCL lines,
and just multiplex the SDA since the I2C devices wouldn't
see a start condition unless SDA was low before SCL was.

Robert

Charles Linquist wrote:

>
> Does anyone know of an I2C temperature sensor that either has a
> programmable address, or has more than 3 address bits?
>
> I need to hang 20 temperature sensors on one I2C bus, and I want
> to make the hardware at the sensor end as simple as possible.
>
>
> Charles Linquist
>
>
>

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[vasile surducan]

On 6/11/05, Charles Linquist <[hidden email]> wrote:
>
> Does anyone know of an I2C temperature sensor that either has a
> programmable address, or has more than 3 address bits?
>
> I need to hang 20 temperature sensors on one I2C bus, and I want
> to make the hardware at the sensor end as simple as possible.

  Alternative suggestion:

  Use any cheap I2c temperature sensor like LMxx and an I2C addresable
bus splitter/level converter like PCA9540 etc.Will be some advantages
when you'll find broken sensors.

http://www.national.com/VCatalog/view.cgi/?command=toggleSort&attr1=Accuracy&attr2=0&a2=Accuracy%2F%2Fv%3A8&a3=Quiescent+Current%2F%2Fv%3A8&a4=Resolution+degCperLSB%2F%2Fv%3A8&a5=Interface+Type%2F%2Fv%3A8&s0=PNumber%2F%2F1&a1=SubCategory%2F%2Fv%3A8&a0=Category%2F%2Fv%3A8&m1=SubCategory&t=0&m2=Bpn&m0=Category&as=0&render=1&domains=PNumber&q=25&i=PNumber&c1=e%3A0%2F%2FSubCategory%2F%2F%3Aeq%2F%2FDigital&c0=e%3A0%2F%2FCategory%2F%2F%3Aeq%2F%2FAnalog+-+Thermal+Management&tId=67

or:
http://www.maxim-ic.com/Sensors.cfm

Vasile

>
> Charles Linquist
>
>
>
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[Mark Jordan-6]

On 11 Jun 2005 at 9:14, vasile surducan wrote:

>
> http://www.national.com/VCatalog/view.cgi/?command=toggleSort&attr1=Accuracy&att
> r2=0&a2=Accuracy%2F%2Fv%3A8&a3=Quiescent+Current%2F%2Fv%3A8&a4=Resolution+degCpe
> rLSB%2F%2Fv%3A8&a5=Interface+Type%2F%2Fv%3A8&s0=PNumber%2F%2F1&a1=SubCategory%2F
> %2Fv%3A8&a0=Category%2F%2Fv%3A8&m1=SubCategory&t=0&m2=Bpn&m0=Category&as=0&rende
> r=1&domains=PNumber&q=25&i=PNumber&c1=e%3A0%2F%2FSubCategory%2F%2F%3Aeq%2F%2FDig
> ital&c0=e%3A0%2F%2FCategory%2F%2F%3Aeq%2F%2FAnalog+-+Thermal+Management&tId=67
>

        That 400+ characteres link can be changed to:

        http://tinyurl.com/8xp6t

        Using the Tinyurl.com website. Take a look.


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[Chris Levin]

 
If you decide to take this approach then you should consider looking at
the Microchip TC74 sensor. It's available with 8 different addresses and
it's easy to use.

Chris

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-----Original Message-----
From: Robert Rolf [mailto:[hidden email]]
Sent: Saturday, June 11, 2005 12:04 AM
To: Microcontroller discussion list - Public.
Subject: Re: I2C temperature sensors

Have you considered splitting the I2C bus into sections using analog
switches? Each downstream segment would need it's own pullup resistors,
but you could have as many buses as you needed. Something like a
74HC4051 should work as an 8 channel switch if you only have
8 loads (sensors) per leg.


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