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Thread: New HM 4.3 Build HM Not Communicating

  1. #11
    TVWBB Honor Circle Bryan Mayland's Avatar
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    That's exactly what you'd get if the MOSFET is fully off, like 0% output. Was the output set to 100%? If so then it means Q1 isn't turning on, because that is what turns on the blower MOSFET. In that case check the 0+ leg closest to the front of the board and verify it has the same voltage as BLW on the microcontroller. If it is 3.3V, then that means the HeaterMeter is trying to turn it on but it isn't, which is usually an indicator of a broken leg on Q1.

    If Q1's close pin is just 0V with no variation then it sounds like the blower output is 0% for some reason, perhaps in the webui the blower has some configuration that is preventing it from running? Not sure at that point.
    I'm that HeaterMeter guy what ruins everybody's free time.

  2. #12
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    Hi Brian,

    Iíve confirmed the blower output is 100% in the webui and have experimented by changing the set point to also force it to 0%. When the fan is at 100% the 0+ pin goes to 3.3v as expected and when the fan drops to to 0% the 0+ pin of Q1 drops to 2.9mV. The closet pin of Q1 does vary, but only within a few mV (.1mV at 0% and .7mV at 100% fan)

    During all of these changes, the center pin of the MOSFET never changes much and hovers around 88 to 91mV with the Blow pin at the RJ jack steady at 206mV.

    With the MOSFET not really changing the center pin output is it possible Iíve damaged the MOSFET somehow and should consider replacing it?

    Thanks for everything!
    Dale

  3. #13
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    Maybe these notes will help you. There are more notes on my v4.2 image so I am including it, the circuit is the same as v4.3 but the layout is different.

    If the center pin of Q1 is going from 0/3.3V when blower is off/full but the trace that connects Q1 to Q3 isn't going from 12/0V you probably have a bad Q1. Also verify Q1 is a BS170...



    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.

  4. #14
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    Thanks for the information Ralph! That pretty much sews it up I think. The leg from Q1 to Q3 never varies from 12v whether the fan is full on, full off or anywhere in between. Apparently Iíve damaged Q1 somehow as it appears the solder connections look good and I donít see any broken leads. Iíll order another BS170 or two and replace it to see if that solves the issue. Iíll post back as soon as I get the part and can get it swapped out. (I also confirmed I didnít have it switched with the MCP1700.

    Thanks again!
    Dale

  5. #15
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    Brian and Ralph - apologies for the delayed update regarding your suggestions. Been a little busy on this end, but finally had the opportunity to swap out Q1 and, as expected, that solved the problem! Fan turns on and output varies as it should. Thanks so much for all the great advice and the time you guys spend on this project and the forum. Now to find some time to actually use the HM in practice!

    Thanks again for everything!
    Dale

  6. #16
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    Glad you got it working. Those little transistors can be overheated during soldering, you're not the first one to take one out....
    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.

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