Thermocouple MAX31855 breakout reports "

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hcgord
 
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Thermocouple MAX31855 breakout reports "

Post by hcgord »

I'm having issues with my Max31855 thermocouple breakout board. I purchased it awhile ago (1 year) but I'm just getting around to using it now. I hooked it up as per the instructions and voila it worked. Or so I thought. It ran just fine for awhile but then I noticed it was having intermittent errors and was reporting "Something wrong with thermocouple!" It seemed to sometimes get worse over time. I tried putting the capacitor across the thermocouple inputs but it didn't seem to help. I've scoured the forums and the internet and tried most everything. I checked my connections to the breakout board, even going so far as to unsolder my connections and redo them. I can't see them being the issue. I tried different digital pins but that didn't help. Sometimes when I switch the power from 5V to the 3.3V pin on my Uno it seems to clear up but only for awhile and not always.

I also found a forum post where adafruit support suggested changing some code in the library so the serial monitor would output the actual error code. This didn't really help because it seems to be a different error code most every time. It's not consistent. However I don't understand the code and it isn't the same as what was found in the other post. I've attached my serial output.

So I'm at a bit of a loss. Could my breakout board be defective? My Uno is new. The thermocouple is new and a type k with 3 feet of cable. I have nothing else hooked up. Could the power supply on my Uno be flaky?

Frustrating because it works but not always!

Thanks,

Gord

(This is a small piece of the output I'm getting). The code I'm using is just the sample code but I've fiddled with the digital pins and changed the delay to 5 seconds. Nothing that should affect anything.

MAX31855 test
Internal Temp = 20.44
C = 24.25
Internal Temp = 20.44
Error - 1851472
Something wrong with thermocouple!
Internal Temp = 20.44
C = 24.50
Internal Temp = 20.44
Error - 1851472
Something wrong with thermocouple!
Internal Temp = 20.44
C = 24.25
Internal Temp = 20.44
C = 24.00
Internal Temp = 20.50
C = 24.50
Internal Temp = 20.44
C = 24.50
Internal Temp = 20.44
C = 24.25
Internal Temp = 20.44
Error - 1851472
Something wrong with thermocouple!
Internal Temp = 20.44
C = 24.50
Internal Temp = 20.44
C = 24.75
Internal Temp = 20.44
C = 24.25
Internal Temp = 20.44
Error - 1851474
Something wrong with thermocouple!
Internal Temp = 20.44
C = 24.50
Internal Temp = 20.44
Error - 1891472
Something wrong with thermocouple!
Internal Temp = 20.44
Error - 1851462
Something wrong with thermocouple!
Internal Temp = 20.44
Error - 1851472
Something wrong with thermocouple!
Internal Temp = 20.44
C = 24.50
Internal Temp = 20.44
C = 24.25
Internal Temp = 20.44
Error - 1851462
Something wrong with thermocouple!
Internal Temp = 20.44
C = 24.25
Internal Temp = 20.37
Error - 1891462
Something wrong with thermocouple!
Internal Temp = 20.44
C = 24.25
Internal Temp = 20.44
C = 24.00
Internal Temp = 20.37
C = 24.50
Internal Temp = 20.44
C = 24.50
Internal Temp = 20.44
C = 24.25
Internal Temp = 20.44
Error - 1851472
Something wrong with thermocouple!
Attachments
serial_screen_error_codes.txt
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hcgord
 
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Re: Thermocouple MAX31855 breakout reports "

Post by hcgord »

Some photos of my setup.
Attachments
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P1070008_resize.JPG (104.5 KiB) Viewed 190 times
P1070007_resize.JPG
P1070007_resize.JPG (76.36 KiB) Viewed 190 times
P1070006_resize.JPG
P1070006_resize.JPG (142.18 KiB) Viewed 190 times

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hcgord
 
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Re: Thermocouple MAX31855 breakout reports "

Post by hcgord »

Okay I'm going to answer my own problem. After much searching and troubleshooting I think I have an answer. Apparently this breakout board does not support grounded thermocouples! That would have been nice to know at the start. It works fine when I'm monitoring the temp via the serial monitor on my laptop (on battery power) but as soon as I plug the power supply into my laptop.. voila errors..

Would be nice if Adafruit stated on the main page that the thermocouple can't be grounded. To their credit it is stated in the tutorial section. My thermocouple needs to be in direct contact with my woodstove. I'll just get an Aluminum Oxide insulator and it should work. However it would have been nice to know ahead of time.

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