Howdy-
I've been reading that one of the default ways to control motor speed is by employing a PWM scheme. But is it possible to use a voltage divder (with a potentiometer to vary the voltage) connected to the upper and lower power supply of an H-bridge? It seems like that would me much simpler, but I'm sure that there's a reason that would not work. Plus, I can only visualize the upper part of the circuit using the divider; I'm not sure how the lower part would go together, but I'm thinking of something like this (pardon the drawing-- using Paint to keep file size under 4k)
No, it does not remotely work. Practically all the power ends up in the resistors.
Well, yes it does sort of work if you are prepared to throw 95% of your power
into heat and buy massive power resistors, but that's so 18th century.
PWM puts all the power into the motor. It can be 95+% efficient with ease.
Motor windings provide a free inductance that smooths the current response
given a suitable frequency of PWM.
A resistor divider circuit is for creating a voltage that's a fraction of an input
voltage, and expects to be driving a very high impedance load (otherwise the
divide ratio is influenced by the load).
You can control a DC motor using a series power resistor (rheostat) but it gives
a mix of torque and speed control, so its not good at either. And it wastes lots of
power (not as bad as a divider though).
