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TR21 reverse engineered

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Pascal Roobrouck edited this page Feb 17, 2020 · 2 revisions

With some luck, I was able to find the schematics of the TR21 on the web TR21 schematics It's pretty simple to understand how this works:

  • it's built around an LM324 quad opamp
  • two opamps are used to generate two voltages (~9 and ~15V) which are fed to a potentiometer which sets the wanted temperature
  • a thermistor generates a voltage for the actual temperature
  • the two voltages are compared and the difference is amplified to yield the 0-24V signal, for a temperature gap of around 3 degrees.

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TR21 Reverse Engineered

21st Century alternative

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