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Max 31855 problems
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Max 31855 problems

by NewmanWVUM on Wed May 12, 2021 5:59 pm

I am using a Max31855 to connected to a raspberry pi 4 and I get readings of 0.0 no matter what mini-k thermocouple I use. I can use other non adafruit 31855 boards(Chinese boards from amazon) and they will give me the temperature readings I expect. One weird thing that I have noticed is that when I disconnect the ground from the board and run the script, I will get a correct temperature read just one time, and when I reconnect ground to the board and run the script it returns 0.0 Ive tried a couple boards and have soldered the jumpers directly to the board and also used the pins that come with the board and attached jumpers. Same outcome.

Script is pretty basic:
Code: Select all | TOGGLE FULL SIZE
import time
import board
import busio
import digitalio
import adafruit_max31855

spi = busio.SPI(board.SCK, MOSI=board.MOSI, MISO=board.MISO)
cs = digitalio.DigitalInOut(board.D5)

max31855 = adafruit_max31855.MAX31855(spi, cs)
tempC = max31855.temperature
print("T:{}".format(tempC))


Really need some help. Any advice is appreciative.

NewmanWVUM
 
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Re: Max 31855 problems

by mikeysklar on Wed May 12, 2021 6:36 pm

Please post a photo of your wiring of the max31855 to the pi4 and any soldering you might have done so we can help you troubleshoot this.

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Re: Max 31855 problems

by NewmanWVUM on Wed May 12, 2021 6:56 pm

Sure. See the images attached.

pi copy.png
pi copy.png (411.11 KiB) Viewed 249 times


boardBack.png
boardBack.png (1016.21 KiB) Viewed 249 times


boardFront copy.png
boardFront copy.png (389.14 KiB) Viewed 249 times

NewmanWVUM
 
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Re: Max 31855 problems

by mikeysklar on Thu May 13, 2021 11:10 am

Your wiring to the Pi, soldering on the Max31855 and code all look great.

Have you tried removing the ARTIK fan hat from the equation? I ask in that maybe it is trying to use GPIO5 (your CS pin) or something silly like that is creating a conflict for SPI to work properly.

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Re: Max 31855 problems

by NewmanWVUM on Thu May 13, 2021 11:27 am

I did try removing the artik fan and put the jumpers on the pi board. All with the same results. Im really stumped as to what is going on. I have other 31855 boards that it will work (some ada brand, some not), and the Ive tried these 4 boards so far and nothing but 0s. These are all stored in the same location and each individually wrapped so the likelihood of them getting fried is very very slim. I can take a working board/wire combo from another pi, put it on the on the one imaged above and it will work fine.

NewmanWVUM
 
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Re: Max 31855 problems

by mikeysklar on Thu May 13, 2021 11:43 am

I just walked away for a moment and realized there is an issue with your wiring. You might be using the 5v out from the Pi, but you want to use the 3v to the Max3155 as the Pi cannot handle a 5v in. It's not totally clear from you photo if the grey wire is on the 3v3 or 5v pin.

https://learn.adafruit.com/thermocouple ... -2997982-3

Pi 3.3V to sensor Vin
Pi GND to sensor GND
Pi SCLK to sensor CLK
Pi MISO to sensor DO
Pi GPIO 5 to sensor CS
Attachments
pi-31855.png
pi-31855.png (261.8 KiB) Viewed 236 times

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Re: Max 31855 problems

by NewmanWVUM on Fri May 14, 2021 9:58 am

Sorry I thought I replied to this. The jumper is on the 3.3V pin.

These boards may just have ended up bad. I need to get 15 more for a project I am doing. Does Ada have a QA process on the boards to make sure they report in correctly? If I order the 15 extra I need, if I open 1 or 2 and am getting the same results what is the return policy like?

NewmanWVUM
 
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Re: Max 31855 problems

by mikeysklar on Fri May 14, 2021 12:22 pm

I would be surprised if this is an issue with our hardware. What are you using for a temperature probe?

We have a QA process when the boards are stuffed. The 30-day return policy is excellent. If you order more please contact us immediately with any issues you see. No need to open all 15 if you see it on another unit lets continue this thread.

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Re: Max 31855 problems

by NewmanWVUM on Fri May 14, 2021 2:28 pm

mikeysklar wrote:I would be surprised if this is an issue with our hardware. What are you using for a temperature probe?

We have a QA process when the boards are stuffed. The 30-day return policy is excellent. If you order more please contact us immediately with any issues you see. No need to open all 15 if you see it on another unit lets continue this thread.


We have 2 mini K probes that we are using from Grainger(linked below). The ones we have out now report in just fine, Ive got about 10 out in our environment. Thats good to hear about the return policy, I would have brought this up sooner but we but a couple boards back in September and then haven't run into any issues until now. I need to get this project moving so I will probably order the 15 next week, and touch this thread if I have any issues.


https://www.grainger.com/product/OAKTON-Mini-K-Thermocouple-Immersion-8TNG9?searchQuery=8TNG9&searchBar=true

https://www.grainger.com/product/GRAINGER-APPROVED-Mini-K-Thermocouple-Immersion-5RMF5?searchQuery=5RMF5&searchBar=true

NewmanWVUM
 
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Re: Max 31855 problems

by mikeysklar on Mon May 17, 2021 4:42 pm

The Max31855 is supposed to work great with k-type thermocouples. You might want to test with one of our k-types in the mix as well to rule out any possibility of compatibility issue (there should not be).

https://www.adafruit.com/?q=thermocoupl ... =BestMatch

If this turns out to be probe compatibility we do have another board which can work with many types of thermocouples.

Adafruit Universal Thermocouple Amplifier MAX31856 Breakout
https://www.adafruit.com/product/3263

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Re: Max 31855 problems

by NewmanWVUM on Mon May 17, 2021 4:56 pm

I'll take that into consideration. I just placed an order for 15 of the max31855 boards today. I guess I am stuck on the fact I got 10 of these working with those probes and then all of a sudden a bunch of zeros. If you have any other hardware that might be a little more convenient I'd be open to suggestions. Would be great if we could get this in a hat board or something and not mess with all the solder joints and jumpers.

NewmanWVUM
 
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Joined: Fri Sep 18, 2020 8:13 am

Re: Max 31855 problems

by NewmanWVUM on Tue May 25, 2021 1:32 pm

mikeysklar wrote:I would be surprised if this is an issue with our hardware. What are you using for a temperature probe?

We have a QA process when the boards are stuffed. The 30-day return policy is excellent. If you order more please contact us immediately with any issues you see. No need to open all 15 if you see it on another unit lets continue this thread.


So I received the 15 boards and the first one I opened nothing but zeros. I have an adafruit thermocouple that I tried as well, still 0.0's when I run the script. I have some off brand Chinese boards from amazon that I ordered, soldered the connection, pinned them on the same pi using the same thremocouples, and it reads as I would expect. This leads me to conclude that there is something up with the adafruit Max 31855 board. I have plenty of pictures of both the adafruit board and the Chinese board if I need to post them. I'd like to return the adafruit boards, how can I get started on that process?

NewmanWVUM
 
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Joined: Fri Sep 18, 2020 8:13 am

Re: Max 31855 problems

by mikeysklar on Tue May 25, 2021 2:28 pm

@NewmanWVUM,

If you would like to return the thermocouples please send an e-mail to support@adafruit.com requesting the return. You will need to link to this forum thread and provide your invoice number.

We can continue to troubleshoot this as well if you are up for it. I see another forum thread with a user in a similar setup getting a 0C reading so I think this problem is not unique to you. It will come down to our CircuitPython library or board itself.

viewtopic.php?f=19&t=178479

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Re: Max 31855 problems

by NewmanWVUM on Tue May 25, 2021 5:09 pm

mikeysklar wrote:@NewmanWVUM,

If you would like to return the thermocouples please send an e-mail to support@adafruit.com requesting the return. You will need to link to this forum thread and provide your invoice number.

We can continue to troubleshoot this as well if you are up for it. I see another forum thread with a user in a similar setup getting a 0C reading so I think this problem is not unique to you. It will come down to our CircuitPython library or board itself.

viewtopic.php?f=19&t=178479


Thanks Mike, I will get the return started and email support. I'm a big fan of your products so if I can help contribute in any way, I will absolutely do so if time permits.

NewmanWVUM
 
Posts: 8
Joined: Fri Sep 18, 2020 8:13 am

Please be positive and constructive with your questions and comments.