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Thread: Heatermeter Aux. Thermocouple And two probe board V6.1(Final Version)

  1. #131
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    Quote Originally Posted by RalphTrimble View Post
    Yes, the basic idea is the tc amp is inside the RD3 so the TC can plug directly into the TC amp (as is required) and the output of the amp can push down the CAT5 cable without issue (without using special TC extender cables). The board can also be used to add a TC to a HM that does not have one.
    Thanks Ralph! Looks like a good way to keep the HM out of the elements or out of a curious kid's hands.

  2. #132
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    Quote Originally Posted by J Halvo View Post
    Thanks Ralph! Looks like a good way to keep the HM out of the elements or out of a curious kid's hands.
    It also let's the thermocouple display temperature below 32F, with some adjustments prior to using that functionality of the adapter board.

  3. #133
    TVWBB Honor Circle Bryan Mayland's Avatar
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    Kinda thinking out loud here, so let me know if you have any thoughts.

    I'm looking at expanding the probe offset system to accept a larger range of values possibly, for better supporting TC amplifiers with offsets and allowing lower temperatures to be read (down to -200C or something). I want to make sure that this board is still well supported by the new configuration. I see that it uses an opamp to provide a low impedance reference voltage to the amplifier, but the reference voltage is set with a potentiometer, is that correct? I'm going to assume this is because HeaterMeter didn't support an off-the-shelf bandgap reference (1.25V / 250C offset) is that correct?

    I'm trying to decide if I am just going to add another probe type "Analog Thermocouple with 1.25V reference" which is relatively easy to do, or expand the probe configuration field to 16 bit to allow offsets of up to +/-32,000 degrees, up from +/-127.

    The down side of using a 1.25V reference is that the precision of the measurements drops by a factor of 3 for most of the temperature range. The precision currently is around 0.2C up to about 220C, then a not-so-great 0.64C. When using the higher reference voltage, you'll get the 0.64C precision for everything above about -50C. The oversampling and decimation code increases this precision somewhat, theoretically up to 0.05C and 0.16C.
    I'm that HeaterMeter guy what ruins everybody's free time.

  4. #134
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    Yes, I used an op-amp controlled by a trimmer resistor to provide the offset reference voltage to the TC amp on the Aux Thermocouple board.
    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.

  5. #135
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    Hello Everyone, I have a scenario that I can't find addressed previously in this thread (but I may have missed it).

    I don't use TCs, just a couple of Thermoworks thermistors for pit and meat. All I'm looking to do is plug the probes in at the RD3 instead of my HM 4.3.

    If I use the aux board, do I need any components other than the RJ45 jack and the probe jacks (and probably the header pins for the fan/servo)?

    I have a HM4.3 board, do I just need to jumper between probe 0 and 1 and RJ45 pins 1 and 2 on the HM board? Do I need to do anything with a ground or is that already handled?

    Does the standard RD3 box also accept the aux board or is it a different print from the one that takes the hand wired RJ45 plate jack?

    Am I missing anything?

    Thanks for any advice.

  6. #136
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    For standard probes you dont really need the Aux board, you can just add three panel mount probe jacks to the RD3 wiring box (the one with three holes in it), wire them to the CAT5 jack and then add jumpers on the HM board for them and your done. On v6.3 of the aux board we designed it so you can omit the TC parts and install a regular probe jack instead of the TC jack, the pit probe jack 'might" fit into the rectangular opening for the TC probe (haven't tried), or I do have a special box that will fit the Aux board with three standard probes, I have also shared that box with John.
    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. #137
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    Should the probes have a separate ground wire each from the RD3 side (using up all four extra RJ45 pins), can they share one, or can they share the solenoid/fan ground?

    At the HM side, do I need to jumper a probe ground or grounds in addition to the probe signal side?

    Thanks for the help!

  8. #138
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    You want to use all 4 spare wires, three probe leads and a ground. At the HM you can tap the gnd right over to the power jack ground.
    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. #139
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    Does that look correct?

    Do I want to leave the chassis ground tabs on the panel mount jacks open or ground them to the servo/fan ground in the RD3 box?

  10. #140
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    Run ONE ground, lets say you use Pin8, which I would jumper to the GND on the power plug right near by on the HM board. Connect that one ground to the ground lug (sleeve) on all 3 probe jacks on the RD3. Then run the tip from each probe jack to 1,2,7 on the CAT5 jack and jumper 1,2,7 to 0,1,2 on the HM probe header for standard pit probe plus food probe 1 & 2.
    Last edited by RalphTrimble; 08-07-2019 at 04:08 PM.
    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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