More Experiments in Servo-actuated Frequency Displays

January 23, 2017

Using the circuit from Servo controlling circuit, I breadboarded this:
555 servo control using variable voltage
Results in a clean PWM pulse train, however:
  • with pin 7 on the 555 biased to 1.47v, travel is less than 90 degrees between inputs of .7  and 5 v.

January 26, 2017

Adjusted circuit:
  • the input current determines the rotational range of the servo, so we need to place a trimmer pot there
  • waveform is clean and pulses are spaced at a consistent 22ms apart

January 27, 2017

  • tested circuit on my WBR Regen 31m receiver: results are difficult to repeat with any consistency.
  • circuit loading on radio changes calibration—this would make it difficult to use with different radios
  • loading also affects tuning
  • On the positive side, circuit continues to outperform op-amp and Arduino circuits, with no problems of power supply dropouts


I think that it’s time to go back to the Arduino-controlled circuit to see if I can wrangle the power-dropout-reset issue.

Leave a Reply

Your email address will not be published. Required fields are marked *