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Thread: "In Pit" Remote Sensor - Possible?

  1. #1
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    "In Pit" Remote Sensor - Possible?

    I am interested in building a remote temp sensor where the sensor transmitter can actually withstand being in the smoker. It would be used in a commercial smoker with no direct exposure to flames. Nominal temp is 225F, but should be able to survive 250F. It doesn't need to control anything, just transmit the temp, preferably over wifi. One probe is enough.

    I have a heatermeter and really like the graphs and being able to monitor on my phone. I could build or adapt one for this purpose, but I'm not sure about what temps the electronics could survive. Currently, we are using an off-the-shelf wireless thermometer and it's been working okay, but I'd like to have the wifi and graphs like the heatermeter.

    Any ideas, or has someone done this already? Thanks!

  2. #2
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    Two major engineering hurdles. First is a battery that will be happy and safe at that temp. The second is transmitting and receiving a WiFi signal through a metal smoker with a reasonable range.

    It is way cheaper and easier to drill a small hole so the sensor can be on the inside and the power source and transmitter on the outside.

  3. #3
    TVWBB Wizard Steve_M's Avatar
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    Most industrial grade electronics are only rated for a max operating temp of 200F. As Matt suggested, finding a way to easily mount the HM on the outside would be best.

    You could also look into doing some light modifications to the smoker by adding some panel mount 3.5mm jacks that the probes can be easily connected to and removed from.

    Either way, I'd suggest keeping the devices that emit magic smoke out of your food chamber!

  4. #4
    TVWBB Wizard
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    Hm has the ability for wireless probes. Although, the soldering pads for the wireless add-on board is no longer on the HM Circuit board, it still could be added on. Bryan would have more information about it, though.

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    Thanks for the input. The problem with mounting the electronics outside - which would be my preference too - is that these pits have several racks in a sort of ferris wheel configuration, so there's no way to run a wire from a probe to the outside. Currently, the pitmaster is using a regular wireless bbq thermometer. He just sets the transmitter - which you would normally put on the counter - on the rack next to the meat. That's why I though it might be possible to build something with more capabilities that could survive being in the heat.

    Wireless probes sound promising. Where could I find more information about those?

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    https://tvwbb.com/showthread.php?728...ght=rotisserie

    Karl, take a quick look at that thread. There might a possibility of a solution for you.

  7. #7
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    Thanks for the suggestion. Slip rings would do the job, but we can't modify the pit in any way. I'll definitely keep them in mind if I ever add a rotisserie to my home setup!

  8. #8
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    I dont think you are going to be able to put something INSIDE the pit that will wirelessly connect a probe to the HM, the heat, the smoke, the steel are all very tough hurdles for the electronics of a wireless device to overcome. If you can get a regular probe in there with the lead coming out of the smoker connecting to the electronics outside that would be the most logical path to success IMHO.
    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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    Okay, thanks.

  10. #10
    TVWBB Platinum Member Bryan Mayland's Avatar
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    Yeah it would be pretty difficult to build a battery powered transmitter that worked at that temperature. The people over at Meater have done it with an all-in-one probe that transmits meat and pit temperature via bluetooth but it seems like an awful environment for a LiIon battery, whose max safe discharge temperature is 60C. Even "high temperature" capacitors are only rated to 105C and you'll definitely have problems with their electrolytic fluid drying up and becoming worthless over time.

    The HeaterMeter v4.2 boards had an expansion header on them for connecting an RFM12B module for doing 915MHz wireless probe data transmission. It was created because one user way back in the day wanted do be able to connect his probes on his rotisserie without the cables getting all tangled up. The board/schematic for the receiver is the RfAddon files in our repository and a sample transmitter is the LMRemote schematic/board. The 4.3 HeaterMeter doesn't have this expansion header any more but the software still supports it and the ATMega pins sit unused so it would be trivial to add it with a few wires and an RF module.

    So if it's what you're into, I'd suggest an LMRemote on the outside for the food probes that rotates with the rack if possible. For the pit probe you probably don't want that going round and round into hotter and colder areas because that would make it hard to control the temp. Thermocouple wiring is pretty small though so there's got to be a way of getting the pit probe inside, stationary, and in an acceptable location for control.
    I'm that HeaterMeter guy what ruins everybody's free time.

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