@tpowell1830 Thanks for the warm welcome!
I'm excited to join in on the journey.
No one can guess what happened to your circuit if we don't know what it is.
True dat... see attached.
Third, if you do a google search for "thermocouple op amp circuit", you will get a boatload of examples.
In my googling I've mostly found things where a newbie is asking a question and the thread quickly goes dead - like this one, for example:
https://forum.arduino.cc/index.php?topic=546682.0I've also found things were people just say "it's too hard, pay $15 at Adafruit or $8 at DigiKey for an ASIC".
@kosine Thanks.
I've also found links like the one mentioned above (
https://www.electroschematics.com/12610/how-to-play-with-thermocouples/ ) that show a diagram that can ostensibly be used with any 50¢ op amp and explain that theoretically it'll work, but I haven't found anyone saying "yeah, I did this, and here's the problem I had, and here's how I realized what I was doing was wrong and here's the working end result".
Case and point (in the article linked above):
Because I had limited time and resources, I purchased a microcontroller-compatible MAX6675 thermocouple module and a K-type thermocouple from eBay.
People
say you can do it, but I haven't had success and I haven't found a thread anywhere where the person posting the question comes back to say "thanks, that worked!" or "I figured it out, here's how:"
I'm not quite sure how, but so far I've burnt 90¢ worth of op amps. I'm okay burning another $15 worth of them if that's what it takes to learn. However, if I can skip ahead a little and only burn another $2 worth, that would be great too.
What would be most excellent would be if someone who is more experienced and also has some spare op amps, batteries, resistors, and thermocouples laying around happened to have the bug of curiosity bite them and come back and say "yeah, I got it working in a jiffy with link-to-schematic and an LXNNN" or, perhaps more likely, something like "I tried, but oddly I couldn't get a reading until 100˚C and it was only stable within 20˚C, which sucked, so I added an x value cap which kinda helped, but I think that the X, Y, or Z parameters aren't fit for this, I bet one that has improved Z or adding a Q in series would work great. Be careful not to touch the in+ to the output on your breadboard while in- is grounded otherwise you'll break it but still get random readings, which will lead you down a rabbit whole of sadness".
(meanwhile I'll also be trying it out, but I think I may order a different type of op amp and it may take a few days for me to resume my journey)
Here's my schematic (attached).
P.S.
@jysd Once I get a reading that's anywhere in the reproducibly measurable range at all, I'll keep that in mind. Thanks.
@soldar It's just a cheap-o multi-meter (BTMETER BT-770M). In fact I'm using a different thermocouple than what it came with because the plastic wasn't rated for the temps I wanted.