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Thread: Kudos to Bryan!

  1. #31
    TVWBB Guru Steve_M's Avatar
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    Bryan,

    Are you doing any ADC oversampling on the ESP8266?

    I just spent another $5 for one of those ADS1115 boards that has 4 x 16 bit ADCs on it.
    Last edited by Steve_M; 10-08-2018 at 08:54 AM.

  2. #32
    TVWBB Honor Circle Bryan Mayland's Avatar
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    I find the ADC is pretty noisy on them, or more likely the board designs of these cheap modules may not be noise immune, so all I've done is use simple averaging in a read 4x and divide by 4 manner. A better algorithm would probably be a median filter, throwing out the high and low values because most of the noise I have seen is like one sample is just way out.

    I also had a line of people when I first opened up the brewery but I think the newness wore off because now people aren't willing to clear their whole day's calendar to sit in a hot Florida garage around a giant boiling pot just to get some free delicious beer.
    I'm that HeaterMeter guy what ruins everybody's free time.

  3. #33
    TVWBB Guru Steve_M's Avatar
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    I don't find the noise to be too bad, but I think that's more of a tip of the hat to the signal coming out of the AD8495 TC amp. When I switched from the Arduino Nano to the Wemos D1 Mini, I gained a good 50% boost in ADC resolution going from a 5v board to a 3.3v board. That resolution boost was very noticeable in how the PID loop reacted to the input from TC amp. I'll be interested to see how much better the control will be once I've got the new 16 bit ADC doing the input readings.

  4. #34
    TVWBB Honor Circle Bryan Mayland's Avatar
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    The ADC worked pretty well for me but one reading in 10,000 would be way out which would sort of mess with the system I had. I had a know which controlled the power output from the device, but you could also set the output from the webui. As long as the knob stayed within 2% of the last manual value, it wouldn't change power outputs and run off either the last digital set value or the last manual value. It works great but every few hours I'd see the power output change because I got one set of ADC readings that was far enough off from the last manual set that it would fall outside the 2%, changing the output, then it would go back to within the 2% and reset back to the last manual value. This had the effect of disabling digital control because every few hours it would just go back to whatever the knob was at, with one update changing the power to an erroneous manual value, then back to the last manual value.

    You can get 5x the ADC resolution on the Nano by using the bandgap reference instead of AVCC to measure the thermocouple, which is good to 1100mV/5 = 220C. That's what HeaterMeter does. The 1V ADC limitation of the ESP8266 would bring that down a little lower, but you're making a divider to feed the ADC anyway so you can scale it down to whatever range you want. Although if this is for sous vide I'd recommend just clamping the output of the amplifier to 1V and not using a divider going into the ESP.
    I'm that HeaterMeter guy what ruins everybody's free time.

  5. #35
    TVWBB Guru Steve_M's Avatar
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    If the 16bit ADC doesn't work out, I'll look into clamping the voltage.

    Tonight's accomplishment.

    Writing out JSON data with ArduinoJSON and figuring out Google gauge charts. There are nicer looking D3 based gauges, but I'm so weak when it comes to the Front End/UI that I'm taking it in baby steps.

    Look, Mom! Real time updating gauges!


  6. #36
    TVWBB Guru Steve_M's Avatar
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    Look how small that 4 x 16bit ADC is!


  7. #37
    TVWBB Guru Steve_M's Avatar
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    So I got the the new ADC integrated into the current setup and now my temps are all over the map.

    Everything worked fine on the breadboard, with the only difference being the Adafruit AD8495 board with the reference voltage on it.

  8. #38
    TVWBB Guru Steve_M's Avatar
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    Well, this is annoying. I just swapped in the Adafruit AD8495 board and things are rock solid now. I'm not sure if it has to do with the additional 1.24v reference voltage boosting the signal on the Adafruit module or perhaps some of the different components on the input side such as:

    HM:
    10K resistors on TC + and -
    1K on TC- to GND
    1n caps on TC + and -
    10n cap between TC + and -

    Adafruit:
    100 Ohm resistor on TC + and -
    1M on TC- to GND
    .01u (10n) caps on TC + and -
    .1u (100n) cap between TC + and -

  9. #39
    TVWBB Guru Steve_M's Avatar
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    I removed the 1K between TC- and GND and replaced it with a 100K and it didn't make any difference. Still seeing temps fluctuate +/- 5C during readings. Looks like my quest for high resolution readings continues. The HM TC board worked no problem when connected to the 10 bit ADC on the Arduino or the ESP8266. It's only when connected to this 16bit ADC that it's acting up.

  10. #40
    TVWBB Guru Steve_M's Avatar
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    Uh-oh! The noise is coming from inside the house!

    The My HM 4.2 franken-tc board is working fine on the breadboard, but not on the cobbled up PCB. The path from the screw terminal on the PCB to the TC board must be wonky and needs to be cleaned up.

    Plot Twist: The breadboard setup runs great from a USB battery pack. When powered from a USB wall adapter, the temps start fluctuating again.

    I should probably figure out how to make a proper schematic and get a PCB made for this thing.

    Last edited by Steve_M; 10-22-2018 at 07:16 PM.

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