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 max 31865 3-wire configuration
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- mikeysklar
- Posts: 13936
- Joined: Mon Aug 01, 2016 8:10 pm
Re: adafruit max 31865 3-wire configuration
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.
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.
- emgimneer
- Posts: 8
- Joined: Wed Jun 02, 2021 12:17 pm
Re: adafruit max 31865 3-wire configuration
I tried those steps and got a fault, is this related? I did not turn up any results when i googled the problem.
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- emgimneer
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Re: adafruit max 31865 3-wire configuration
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?
- mikeysklar
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Re: adafruit max 31865 3-wire configuration
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.
- emgimneer
- Posts: 8
- Joined: Wed Jun 02, 2021 12:17 pm
Re: adafruit max 31865 3-wire configuration
That's solved the characters, thank you, but its still reporting -242.2 degrees. Do you know how to resolve this?
- emgimneer
- Posts: 8
- Joined: Wed Jun 02, 2021 12:17 pm
Re: adafruit max 31865 3-wire configuration
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.
- mikeysklar
- Posts: 13936
- Joined: Mon Aug 01, 2016 8:10 pm
Re: adafruit max 31865 3-wire configuration
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?
Can you post photos of the third unit?
- emgimneer
- Posts: 8
- Joined: Wed Jun 02, 2021 12:17 pm
Re: adafruit max 31865 3-wire configuration
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.
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- rtd mine.png (313.07 KiB) Viewed 698 times
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- rtd mine.png (313.07 KiB) Viewed 698 times
- emgimneer
- Posts: 8
- Joined: Wed Jun 02, 2021 12:17 pm
Re: adafruit max 31865 3-wire configuration
Alright, pulled in even more help and finally got the last one to work. Probably.
- emgimneer
- Posts: 8
- Joined: Wed Jun 02, 2021 12:17 pm
Re: adafruit max 31865 3-wire configuration
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.
- mikeysklar
- Posts: 13936
- Joined: Mon Aug 01, 2016 8:10 pm
Re: adafruit max 31865 3-wire configuration
@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.
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.
Please be positive and constructive with your questions and comments.