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adafruit max 31865 3-wire configuration
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adafruit max 31865 3-wire configuration

by emgimneer on Wed Jun 02, 2021 12:22 pm

Hello, i have some questions about configuring the max 31865 for a 3 wire rtd. The instructions say to cut a trace on the right side of the pcb, but im not certain which one its referring to, I've asked some EE students and they don't know either. I've attached the instructional reference photo, and if someone could circle/mark the location to cut that would be very helpful.

adafruit rtd pic.png
reference photo
adafruit rtd pic.png (266.62 KiB) Viewed 654 times

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Re: adafruit max 31865 3-wire configuration

by mikeysklar on Wed Jun 02, 2021 5:59 pm

Hello @emgimneer,

You will want your 3-wire RTC setup to look just like the photo you included.

The left side of the photo with the "2/3 Wire" labeled jumper needs a solder blob.

The right side of the photo with the yellow arrow needs a cut between the 24 pad and 3 pad. Use a exacto to sever the connection and solder blob just on the 3 pad.

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Re: adafruit max 31865 3-wire configuration

by emgimneer on Fri Jun 04, 2021 11:57 am

I tried those steps and got a fault, is this related? I did not turn up any results when i googled the problem.
Attachments
amplifier  error.png
amplifier error.png (17.26 KiB) Viewed 629 times

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Re: adafruit max 31865 3-wire configuration

by emgimneer on Fri Jun 04, 2021 2:03 pm

Further update, i briefly got it to report temperature, but whenever I open the serial monitor it stops reporting and reverts to a string of unreadable characters. This was on my 2nd amplifier and RTD, not the one I used previously, and it has since stopped working entirely. It has reverted to the earlier issue of reporting -242 degrees and a string of characters. I tried again with my third and final amplifier + RTD, which I hadn't even touched yet, but even though I set it up just like the 2nd (when it was briefly working), the third didn't work at all. What do?

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Re: adafruit max 31865 3-wire configuration

by mikeysklar on Sun Jun 06, 2021 6:02 pm

The screenshot you posted looks like a mismatch of serial console speeds. Make sure the Arduino IDE serial console is set to the same baudrate as your code. There is a little drop down menu in the bottom right corner of the serial console.

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Re: adafruit max 31865 3-wire configuration

by emgimneer on Mon Jun 07, 2021 11:03 am

That's solved the characters, thank you, but its still reporting -242.2 degrees. Do you know how to resolve this?

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Re: adafruit max 31865 3-wire configuration

by emgimneer on Mon Jun 07, 2021 1:59 pm

Another update, the first two are now working, for the most part, but the third one isn't. I tried a few different things with the soldering on each, but when i try to recreate it on the third amplifier its still nonfunctional.

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Re: adafruit max 31865 3-wire configuration

by mikeysklar on Mon Jun 07, 2021 5:32 pm

What was the necessary change you had to make to the first two? Usually it is just the probe is not connected correctly if you are gettin a -242.

Can you post photos of the third unit?

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Re: adafruit max 31865 3-wire configuration

by emgimneer on Tue Jun 08, 2021 11:25 am

From what I recall, I just undid my soldering on the first two and tried to cut deeper, then re-soldered them. They really shouldn't be any different at this point though since that's more or less just what i did to the third from the beginning.
Attachments
rtd mine.png
rtd mine.png (313.07 KiB) Viewed 516 times
rtd mine.png
rtd mine.png (313.07 KiB) Viewed 516 times

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Re: adafruit max 31865 3-wire configuration

by emgimneer on Tue Jun 08, 2021 2:34 pm

Alright, pulled in even more help and finally got the last one to work. Probably.

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Re: adafruit max 31865 3-wire configuration

by emgimneer on Fri Jun 11, 2021 10:53 am

Alright, well they worked for all of 2 days, and now its the same issue again. -242.2, no matter which amplifier or rtd I use, and nothing I do seems to fix it. I'm not certain what the issue is, they were working fine last night and nothing has changed.

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Re: adafruit max 31865 3-wire configuration

by mikeysklar on Fri Jun 11, 2021 4:56 pm

@emgimneer,

This situation of working to not working is most likely a wiring issue. A lose connection or issue with the terminal block? I would try debugging with a multimeter. Go over each connection measuring resistance and looking for anything suspiciously loose.

It might make sense to use a perfboard or more permanent soldered connections (getting off the breadboard) at this point as you have briefly shown that everything was in the correct place.

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Please be positive and constructive with your questions and comments.