I'm looking for a reversable speed controller that uses variable DC input voltage (about 0-20 Volts) to control higher DC (30+ volts) or AC output voltage proportionately. Something like this must exist. If so what type of controller is it?
Thanks for the reply. I think I found a better way to accomplish my goal.
What I found were speed controls (some robust enough to make a go-cart with) for robotics that use PWM signals from receivers used for radio controlled models, and something called a comparator to convert plain DC voltage to PWM signal since I don't have one readily available.
I would like to add itsmoked that I found a 'better way' than my pervious ones. I was'nt saying better than your idea. Just though I would clarify that.