Temp probes are way off


 
R

RWilloughby

TVWBB Member
I smoked a pork shoulder on Saturday and it turned out awesome, best one I've made. I started it at 10:30pm Friday night and it was going great until 11:30am. I checked my display and it was stalled it seemed at 130. I came back at 12pm and the screen was gibberish, box was hot - backing in the mid day sun... I opened the case, brought it inside to cool down. Moved a umbrella over my cooking setup and plugged the HM back in and my display is back, but can't view remotely. I come back an hour later an no change in temp, so I let it go another 2 hrs. Still no change! Something is up, so I grab another thermometer and manually check it, 210... I pull it and wrap it up to rest.

As its resting I bring in my HM and probes. My thermocouple probe is fine, but my Maverick probes are now reading 45 degrees resting on the counter??? I turned it off and tested it again a couple hours later with the same results. When I put my hand on it, the temp raises up a few degrees so they are still somewhat alive. These probes were in the meat and not exposed to anything over 300. So I'm confused why they would be out of wack.

The other casualty to report is my RasPi Zero W... after all the work getting it up and running on the HM, its now dead I believe. As soon as I plug it into a usb power, the board gets really hot. From what I've read, that means its either on its way or its already dead.. I'm not batting too well with this....

So the question is, do I get new probes, or is there something off elsewhere? Until I get a new RasPi, I can't do any in depth testing...
 
Maybe your probe presets got messed up somehow during the melt down... or maybe you blew a voltage regulator on the HM board in the heat, or something else that is making voltages out of wack on your HM board?
I would start out testing the power section of the HM board, 12V, 5V, 3.3v at the respective regulators. The probes themselves only have three components between the probe jack and the AVR, the 10K & 1K resistors and the .1uf capacitor, not the type of circuit where you would expect those components to burn up even in outdoor heat.
As for the rPi, if it's getting hot on a wall wart I wouldn't trust it on your HM, I would get another zero-w and call it a day since they are so cheap.
 
this is the one thing you need to watch out for. My previous Pi3 had issues when it got hot with freeze-up, but mostly the controls would start having a mine of it`s own. I am currently cooking a spatchcock chicken with my heatermeter using a Pi3+ and have not had any temp issues so far. One thing to make sure when using the heatermeter is to stand it up so the display is facing you. This disipates heat well. I think Brian and others hang theirs in the air from their grills. I believe Will Begg has a stand that can be printed. Just find ways to keep cool, and dry and the heatermeter will work well.
As for Maverick probes, i quit using them mainly because of the fit in the connector. If I didn`t insert them just right, they were flakey. Thats when i switched to Thermoworks probes and they fit correctly in the jack..
 
Ahh, maverick probes... I quite using them too, they're too flaky for me. I'm thermoworks all the way, really happy with their probes.
 
Thanks all. Ralph, can you give me some guidance on how to test those regulators? I have a analog multimeter.

I've got a new RasPi coming to me. Once I validate my HM board is still good, I'll order some thermoworks.
 
12v DC measure at power jack (gnd and 12V are marked on the backside of the board). The little OKI DC-DC board takes 12V down to 5V., this device is kinda near the center of the v4.3 board and the voltages are marked on the back side of the board (near the little robot guy). The 3.3v regulator is right next to the OKI, you should be able to see 33 printed on the top side of the board. This one doesn't have voltages marked and I don't recall the pinout, but the 3 pins are gnd, 5v in and 3.3v out. So just ground the black lead of your meter at the power jack and probe the 3 pins, you should see 0V (ground), 5v (input) and 3.3v (output).

If you don't see 5v at the OKI it may be your problem, if you don't see 3.3v at the 3.3v regulator it may be the problem. If both of those voltages are good your power supply is good, you may have a problem in another spot, perhaps in the circuit that feeds the voltage to your pullup resistors (those are the 10K resistors standing on end behind the probe jacks) You should see 3.3v on the leg of these resistors that connect together (look at the underside of the board and you will see how a trace goes from resistor to resistor)

PS you wont regret the move to Thermoworks probes, much better than Maverick IMHO.
 
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Thanks Ralph, I ended up upgrading to the Thermoworks probes and have not looked back! I should have started with these!!
 
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