All I have a home brew GU-84b amp that I don't seem to be able to sell so perhaps I keep it and upgrade a bit. The question is: Do stepping motors, properly used, big enough, etc. keep their position
Markku, Stepper motors will work just fine for your application. Yes, one initializes the motors at power on, and then there is no need for additional control feedback. Initializing is easy with air
Hi Thanks for the ideas. Does anybody have a good idea how to find the "zero point" on vacuum cap without adding a potentiometer for position feedback? I was thinking about reflective optical sensors
Being somewhat cynical, I would rather rely on a system with microswitches to detect the end points rather than electronics - far less to go wrong. It's not difficult to do. 73 Peter G3RZP == Message
Markku, your idea might work on glass variables, but you'd probably have to use laser diodes to focus a beam throught the gap. Another (easier) possibility might be to use the same technique SteppIR
Actually, Peter, I think microswitches would be pretty difficult to implement, since vacuum variables are mult-turn devices. I know there were commercial ETO MRI amplifiers that used vacuum variables