# Op-amp DC motor feedback

Attached I have a circuit I’ve created but I don’t know what’s going on or how it works. I’ve started with an LED and ended up here HA, how should this react. I’ve attached an image the
Two motors are joined via gears like so in the image.

So what does it do?

Seems that the output of the OPAMP is .6 volts...the transistor is working its
Gain and giving me almost 2 volts at dc motor A (non feedback). I'm getting
Somewhat of a saw tooth waveform on a oscilloscope. I am not
Very sure of anything else
Except that.

If you want the motor to run at all, get rid of the 1K resistor in the collector circuit of the transistor. You should also reduce the base resistor, perhaps to 100 ohms. Motors create voltage spikes that destroy transistors and other circuitry, so add a flyback diode.

Motor is screaming, ones got 3
Volts across it and the being drove by the transistor
Controlled motor is producing roughly 1.7…what is the op amp doing for me?

If you size that image so it fits on a computer screen that would be a start.....

Do you have any idea of what you want the motor(s) to do?

You draw one motor with an armature and the other without, is that significant
(like is one part meant to be the field winding?)

If this is anything to do with "Over-Unity" I suggest a course in real physics!

The op-amp circuit with the two 1K resistors at the negative input and the 10k pot is a (inverting) summing amplifier. +12V is summed with the (unknown-variable) voltage into the other 1K resistor (the voltage out of the motor), inverted and amplified by the ratio of the feedback pot to the input resistors.

I have to assume the voltage out of the motor is negative, since 12V amplified by anything more than 1.0 is going to saturate the op-amp and drive it's output to -12V. Have you measured the control/feedback voltage out of the motor?

For example, if you have the pot set to the mid-point that's a gain of -5. If we assume the motor output is -10V, we can sum that with the +12V to get +2V. A gain of -5 will give you -10V out of the op-amp. (That would turn-off the transistor, so it's probably not a realistic static condition, but that's how the op-amp is working. Mathematically, you could also assume you have two inverting amplifiers with the voltages summed at the output (+12 x -5 = -60V, -10 x -5 = 50V... -60V +50V = -10V.

The transistor is a voltage follower to boost the current capability of the op-amp.