MAX - 31850K with I2C safe level shifter bug

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anandswaminathan
 
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MAX - 31850K with I2C safe level shifter bug

Post by anandswaminathan »

Hi,

I have connected 3 MAX 31850K thermocouple amplifiers (with K type thermocouples from adafruit) with aI2C safe level shifter and initially I was getting temperature readings for all three. Then one of them failed and started reporting nan readings (Note that my arduino uno gets the address of the device but does not return the temperature).
Then the other two started acting strangely and froze. They would give an initial reading of around 72F and not change even if I touch it for a long time (It used to respond quite well before)
Now another one of my amplifiers reports nan readings and the other is always frozen at values around 71 +/- 2 (It randomly changes values)

To debug the problem, I rewired everything with only one amplifier (one which gives frozen temperature values) and a new thermocouple, it started working. The other amplifiers which gave nan values do not work at all (their address is detected but no temerature output)
What do you guys think went wrong with the thermocouple and/or amplifier for it to stop working ? I was very careful to handle it with care.
Any thoughts ?
Thanks.

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Franklin97355
 
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Re: MAX - 31850K with I2C safe level shifter bug

Post by Franklin97355 »

Could you detail your parts and connections? A picture or drawing would help too.

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anandswaminathan
 
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Re: MAX - 31850K with I2C safe level shifter bug

Post by anandswaminathan »

Attachments
IMG_20141017_193329.jpg
IMG_20141017_193329.jpg (810.98 KiB) Viewed 420 times
IMG_20141017_193313.jpg
IMG_20141017_193313.jpg (818.8 KiB) Viewed 420 times
IMG_20141017_193320.jpg
IMG_20141017_193320.jpg (876.87 KiB) Viewed 420 times

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adafruit_support_mike
 
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Re: MAX - 31850K with I2C safe level shifter bug

Post by adafruit_support_mike »

It looks like you have the yellow and red lines from the thermocouple on the opposite sides WRT the markings by the terminal blocks, but I can't see the actual wire connections.

Check there to make sure the connections are correct, secure, and that the wires aren't shorting against each other. It won't do any harm if they are, but you wouldn't get any sensor reading.

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anandswaminathan
 
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Re: MAX - 31850K with I2C safe level shifter bug

Post by anandswaminathan »

Thanks Mike,

I will check that and update ASAP. Hopefully that was the problem.

Regards,
Anand

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