all transistor PWM with torque feedback exp.#1

This is an all transistor PWM with torque feedback control circuit, to run a small capstan motor from a VCR, used for experimental purposes.


I'm experimenting trying to see if I could use current feedback in pulses, to control the pulse width output of a schmitt trigger circuit, instead of elaborate tachometer circuits and processors, if I can get the proper sinewave frequency that matches the motor in use, then it seems like this could work fine enough for my purposes.

It seems like the feedback network needs to be biased into its linear region, so any change in motor impedance, will automatically reflect into the feedback network, in real time, with no threshold Vbe delays. If the transistors are biased in switching mode, then the circuit oscillates instead of ramping up and down in pulse width.

The feedback currents needs to ramp in sync, with motor load.

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