Many of you have probably noticed that the internal temperature sensor of the EAF is mostly useless, since it is a sensor on the die of the microcontroller in the EAF, and is not a measurement of ambient temperature -- the more you drive the EAF, the higher that reading goes.

At the same time, for many folks, ambient temperature is good enough, not needing to actually measure the OTA temperature with the external probe that ZWO sells. For those, try this hack.

Here is a photo with parts for two probes, one for a right-angle probe, the other in-line:

The little beads are 100 kΩ NTC (negative temperature coefficient) thermistors (cheap -- about 60 (US) cents a piece at Amazon). The plugs are 3.5mm TRS (tip-ring-sleeve) "headphones plugs."

The thermistor is soldered between the tip and sleeve of the TRS connector. Leave the ring pin of the connector alone since ZWO uses that for the EAF hand controller. Like so:

This is what the right angled one looks like when installed on the EAF:

This is what the straight in-line version looks like:

This is what ASICap shows:

With the external probe unplugged, EAF uses the internal sensor that shows the way-elevated microcontroller die temperature instead of ambient temperature:

Have fun.

Chen

This is the ambient temperature reported by one of the hack probes, compared to a La Crosse wireless thermometer that is about 5 meters away from the EAF.

Chen

    Very nice, Chen! Invaluable information as always. Your solution is such a relief in regards to cable management that is involved with the original external probe from ZWO. I am already considering exchanging the original probe.

    Aloha,
    Olli

    a year later

    Hi, Chen
    Thanks for the EAF tem probe hack. I assembled two of them using generic 100k ohm thermistors purchase on Amazon
    'HiLetgo 10pcs 3D Printer NTC Thermistor 100 K Accuracy 1% B Value Temperature Sensor 3D Printer Parts'
    (not sure if secondary vendor links are allowed).
    Both of my probe tremperatures report temperatures 7-15 degrees higher than the ZWO extgernal probe- which closely matches 2 digital thermometers that I tested it with. I soldered to the tip and sleeve, carefully avoiding the ring tip and any other conttact.

    Could you refer me to the correct thermistor? The generic ones I see are for 3D printers; perhaps the ones I purchased are all junk.

    Many thanks,
    Gary R.

    • w7ay replied to this.

      Gary7 HiLetgo 10pcs 3D Printer NTC Thermistor 100 K Accuracy 1% B Value Temperature Sensor 3D Printer Parts

      That is what I'd used.

      Currently, one of them is showing this, with a La Crosse outdoor probe about 10 or 15 feet away.

      Use an ohmeter to double check if Amazon shipped you the correct part.

      Chen

          15 days later

          Created an account just to tell you it indeed worked. So thanks....

          Bought the exact items you specified from aliexpress and even with my wonky soldering skills it worked great....

          a month later

          w7ay I also made my EAF temperature probe following your instructions and it works perfectly !

          Thank you Mr. Chen !

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