I2C temperature sensors

Charles Linquist · Joined: 07 May 2005 Posts: 28 Location: Campbell, CA

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 · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

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

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 · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

Just curious - are you switching to analog temperature sensors?

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

Just curious - are you switching to analog temperature sensors?

Charles Linquist · Joined: 07 May 2005 Posts: 28 Location: Campbell, CA

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.