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I2C temperature sensors

 
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Charles Linquist



Joined: 07 May 2005
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Location: Campbell, CA

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I2C temperature sensors
PostPosted: Fri Jun 10, 2005 10:15 pm     Reply with quote

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

I need to hang 20 temp sensors on ONE I2C bus, and I want to keep the hardware at the sensor as minimal as possible.
kender



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PostPosted: Sat Jun 11, 2005 10:23 pm     Reply with quote

Hi Charles,

Take a look at MAX6697, although it might have availability problems. It can measure 6 external temperatures and one internal. It doesn't have address pins, but the chip comes in different versions with different hard-wired slave addresses.

You can also multiplex your bus. Arguably, it will still be one I2C bus. Here's one of the app notes about it:
http://www.semiconductors.philips.com/acrobat_download/applicationnotes/AN262_2.pdf

Cheers,
Nick
Charles Linquist



Joined: 07 May 2005
Posts: 28
Location: Campbell, CA

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PostPosted: Sat Jun 11, 2005 11:25 pm     Reply with quote

Since I have to layout a new board for the sensor anyway, I have decided that I'll probably just use a 16F818. It costs less than $2.00. I can use the H/W I2C slave port for the interface to the "main" PIC (18F8722) and either bit-bang an I2C port to talk to a sensor, or use the A/D converter and an analog sensor.

It has enough extra pins to give me access to all 127 I2C addresses.


Charles Linquist
kender



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PostPosted: Wed Jun 15, 2005 12:19 am     Reply with quote

Just curious - are you switching to analog temperature sensors?
kender



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PostPosted: Wed Jun 15, 2005 12:20 am     Reply with quote

Just curious - are you switching to analog temperature sensors?
Charles Linquist



Joined: 07 May 2005
Posts: 28
Location: Campbell, CA

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PostPosted: Wed Jun 15, 2005 6:33 am     Reply with quote

I have always used analog sensors (LM34), but was thinking of switching to digital so I could get more channels. I really like the analog sensors, since, with averaging, I can get resolution to a tenth of a degree or so.
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