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Thread: New HM 4.3 Build - Wonky Pit Probe Port Issue

  1. #1
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    New HM 4.3 Build - Wonky Pit Probe Port Issue

    Hi, I just finished building a HM 4.3 with a Pi Zero W that boots up with LEDs working, it connects to the network, and seems to work with the blower except for something wonky with the pit probe.

    I had intended to use my Maverick 732 probes with the HM (understanding they arenít ideal), but they are flaky in all the probe ports. I plugged in a Weber BBQ probe and it is rock solid stable in ports 1-3.
    The wonky part is that when I have a probe in the pit probe port, the HM display will show ďno probeĒ then high numbers like 843 or 569 degrees, then read a stable temp for a while, then jump around again and go back to no probe then a stable temp (this happens with the 732, Weber, and Ponder probes). I changed the pit probe to port 1 (disabling the pit probe in LinkMeter as recommended in a recent post), and the HM seems to otherwise work perfectly. In an oven test the Weber probe is accurate from ambient to 300 degrees using a 31 offset and the fan goes on and off at the appropriate temps around the set point.

    I was hoping to find out whether someone had seen my pit probe port issues, and had guidance on whether I should take the HM apart and try troubleshooting or use the HM with ports 1-3 and quit while Iím sort-of ahead. Iím electronically challenged, so Iíd prefer not to have to dig back into the HM unless necessary.

  2. #2
    TVWBB Diamond Member
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    The probe circuit is quite simple, see below:
    There is one resistor in series with the probe jack and one capacitor in parallel, plus an additional resistor in parallel for standard probes. Check solder on all those components for Probe 0, and if you have excess flux around there wash it with alcohol and a soft brush (let dry completely!)
    I created the Roto Damper, RD3, HMv4.2 sliding back case, "air-burner" and the "ping-pong" valve in my quest for delicious "set and forget" BBQ.

  3. #3
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    Thank you very much for the reply. I checked the solder on all of the components and used alcohol and a soft toothbrush, then let it dry thoroughly. Unfortunately I get the same result after enabling port 0. I disabled port 0 and will try a cook in the next couple weeks, then see if I should use it as is. Thanks again!

  4. #4
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    Dumb question...is the probe configured correctly....for each ?

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    I haven't been able to find the values required to configure the Weber probe under "custom," and plan on acquiring a Thermoworks probe eventually. The strange thing is that with all of the ports configured the same, the Weber probe has no problems and gives identical readings in ports 1-3 and only gives a weird/flaky read-out in the pit probe port. Although I've gone over the soldering on the pit probe circuit, I'm figuring I messed something up on that circuit and will try using the HM with it disabled.

  6. #6
    TVWBB Diamond Member
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    are you sure probe 0 TYPE is not set to thermocouple? You want type = thermistor
    I created the Roto Damper, RD3, HMv4.2 sliding back case, "air-burner" and the "ping-pong" valve in my quest for delicious "set and forget" BBQ.

  7. #7
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    Thanks, but I did check that. I made sure that all ports were set the same then tried the probe in each port, and consistently port 0 does the random high numbers, "no probe," and a stable reading, then occasionally the cycle repeats. I tried putting the soldering iron on the circuit components/connections and it still does the same thing.

  8. #8
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    You dont have the TC amp (SMD) components on your HM board, right? If not there are literally only 3 components between the probe jack and the ATMega to check.... The pit probe connects to the corner pin in the ATMega...
    I created the Roto Damper, RD3, HMv4.2 sliding back case, "air-burner" and the "ping-pong" valve in my quest for delicious "set and forget" BBQ.

  9. #9
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    No TC components, and the base board assembly went smoothly following the instructions, without any missing or spare parts. Tonight I re-soldered the components, wiped everything down with alcohol, and get the same wonky results for the pit probe and it is rock solid steady for probe ports 1-3. The one thing I noticed is that sometimes the erratic pit probe read-out occurs if I'm moving the probe cable, however slightly (it never happens for ports 1-3). I disabled the pit probe and will try using the HM with port 1 as the pit probe for now. Maybe if I get adventurous in the future I'll try swapping probe components for zero and 3 on the HM board to see if the problem moves as well.

    I'm super-appreciative of the comments and suggestions for trying to resolve this.

  10. #10
    New Member Larry Naylor's Avatar
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    Don't know if this is the right place ( i'm new at this ) But i have a probe issue. Have a heatermeter 4.3 with a thermal couple and 3 thermoworks pro probes.2 weeks ago i did a cook using this as just a thermometer and all went well. Last night i did a 10 hour butt smoke using the rd3 with pblower and servo. The trouble i'm having is food probe 1 says it is 182 room temp, Changed probes and all read the same in probe 1, but works ok in 2 ,3. Did the cook using probe 2 and all worked very well. The only difference from the last cook was i connected the rd3 to it. Did some testing this morning without the rd3 and all the voltages in the probe circuits look good. The heater meter ic configured for thermistor probes from thermoworks and all port are set the same. If some one could point me in the right direction i would really appreciate it This is the third time iv'e tried to post this so hope it goes through.

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