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HeatSnob - Grounding errors with non-supplied probes

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  • MrFreddofrog
    replied
    The other week my heatsnob probe started having grounding issues too. It was fine in the morning but when I went to do a second batch in the afternoon it played up. Very weird. Still works fine until it touches the side of the roaster.

    I thought about trying to fix it but given I had a spare thermocouple I didn't bother.

    I'd suggest just get another (wire) thermocouple, should be about $3-4 from a specialist or $10 from Jaycar.

    Leave a comment:


  • doobs
    replied
    Originally posted by gobears View Post
    Also, I experience fluctuations in temperature by a few degrees even at room temperature, over just a few seconds. I would say the swing is +/- 3 degrees celsius, and its killing my ROR curve.
    Is it true that the best solution is just to ensure the probe never comes in contact with the metal of the roaster?
    I am using a Corretto roaster, and the probe goes through a hole drilled in the bread pan.

    Although its impressive, I would rather not build a USB isolator solution!
    I'm having the same problem. I thought it was the Victor, but I bought a Heatsnob and it's doing the same. Are you using windows 10? I reckon they borked the USB performance at some stage. I used to have stable output with XP and Win 8 (I'm pretty sure :P)

    It'd be great if a solution could be found. It's impossible to know what is happening reliably.

    Edit: I have isolated the thermocouple and apart from fixing the grounding issue, it makes no difference to the fluctuations.

    Leave a comment:


  • gazza
    replied
    Just ran a couple of tests with Roastmonitor, the Heatsnob without the USB isolator, with the USB isolator and the Victor DMM, all with the same thermocouple on my desk.

    The scale is 0 to 50° C, Image 1 is the Heatsnob test, the change over to the USB isolator was around 9mins and Image 2 is the Victor.

    Other than the Victor reading a few degree lower it looks OK.


    Gary

    Click image for larger version

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  • MrJack
    replied
    So, probably not the issue

    Leave a comment:


  • gobears
    replied
    Originally posted by MrJack View Post
    Perhaps its a real physical phenomenon? Could the airflow (or temp) over the thermocouple be changing at all?
    Good question. However, it also happens at room temperature, outside the roaster, on each of two different heat snobs with 2 different type k thermocouples from different manufacturers, with the probes well isolated from everything (sitting on plastic).

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  • MrJack
    replied
    Perhaps its a real physical phenomenon? Could the airflow (or temp) over the thermocouple be changing at all?

    In my popper I get cyclical variation in the measured temperature, which I attributed to the position of the bead as it moves around the chamber with the beans.

    Leave a comment:


  • gobears
    replied
    Originally posted by gazza View Post
    I'm a hardware type so so that was a bit of fun, I would say the same about your software driver for Artisan.


    Gary
    Thanks Gary!

    I have hit a rough patch in my quest to make the heat-snob work the way I want.
    Now, I have discovered that I get significant temperature fluctuations, about +/- 2 celsius oscillating with quite some randomness, but following a period of roughly 5 seconds.
    I am using 2 different type K temperature probes, with my Mac, and both show the same behavior.
    I tried running them with the Mac on battery, and on AC power. No difference.
    It also happens when the probes are completely isolated from any metal, at room temperature.

    The internal chip temperature of the Maxim thermocouple interface chip, on the other hand, is rock solid stable.

    This is driving me nuts, and I am very close to trying a phidgets instead, but really like the heatsnob and of course have some emotional attachment due to the time I put into tinkering with the software.

    So, do you think I need the USB isolator to solve this problem, or you have some experience that may say its something else?

    Thanks,
    ~Bruce

    Leave a comment:


  • gazza
    replied
    Although its impressive, I would rather not build a USB isolator solution!
    I'm a hardware type so so that was a bit of fun, I would say the same about your software driver for Artisan.


    Gary

    Leave a comment:


  • Dimal
    replied
    Originally posted by gobears View Post
    Although its impressive, I would rather not build a USB isolator solution!
    The use of a short length of Teflon tube is probably even simpler...

    Mal.

    Leave a comment:


  • gobears
    replied
    Also, I experience fluctuations in temperature by a few degrees even at room temperature, over just a few seconds. I would say the swing is +/- 3 degrees celsius, and its killing my ROR curve.
    Is it true that the best solution is just to ensure the probe never comes in contact with the metal of the roaster?
    I am using a Corretto roaster, and the probe goes through a hole drilled in the bread pan.

    Although its impressive, I would rather not build a USB isolator solution!

    Leave a comment:


  • gobears
    replied
    BTW, you can indeed interface the heat snob to other software, at least you can for Artisan using the code I posted on github. See this post:
    http://coffeesnobs.com.au/home-roast...ons-hacks.html

    Cheers,
    ~Bruce

    Leave a comment:


  • summercrema
    replied
    Upgraded to the latest version of Roast Monitor , problem mentioned in #25 fixed .

    Leave a comment:


  • gazza
    replied
    Just finished a roast with the USB isolated Heatsnob and it worked fine, no more "Thermocouple shorted to ground" errors.


    Gary

    Leave a comment:


  • gazza
    replied
    As none of the other ideas to work around the use of grounded probes are ideal with my roaster I have built a USB isolator and put it and the guts of the Heatsnob in a new enclosure.

    For those interested in the detail the circuit is based on a Analog Devices ADUM4160 USB isolator chip that they kindly sent me as a sample.

    So far it has been tested on the bench and it works fine with the Heatsnob connected, I will get it installed in the roaster later in the week.



    Gary
    Attached Files

    Leave a comment:


  • summercrema
    replied
    Originally posted by johnandcass View Post
    I used a multimeter to check but it seemed fine, so went back to the victor until I could investigate further.
    I have now used some silicone to insulate the probe from the metal visegrips that hold the probe in place and all works well now.
    I used a small silicone baking mould that is food safe and temperature rated.
    I have similar problem for months, I better go get some PTFE Tubing hopefully it fixes the problem. The old Victor never gives me this problem.
    Attached Files

    Leave a comment:

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