PWM --> 3 State Ouptut

[micro571]

I am wondering how easy it is to take a PWM signal and get a digital output. I'm thinking of an RC remote receiver. For motor control that would go from full forward to full reverse. I'd like a 3 state output (Foward / Off / Reverse). If that's not possible, 2 state output would also be ok (On / Off).

Is this pretty easily doable? I have some PIC programming experience. Some PIC IC's have hardware PWM interfaces. Any other simple circuits or ICs that might be able to do the job ??

 

[dknguyen]

If you are trying to drive a motor with a PWM and derive 3 states for the motor from a single PWM signal, that is impossible you must use a PWM in conjunction with another PWM or digital lines.

If you are trying to make an interface for a RC radio to remotely control a uC application, it's pretty easy. YOu just have the MCU measure the PWM being read from the radio receiver and interpret it however you wish. Then you could have a "center" PWM pulse width which would be stop greater or less than that stop width would be a progessively faster forward or reverse. The MCU would be basically reading PWM signals from a radio receiver, measuring them to find out the desire speed you are sending and then the MCU would have to use at least TWO PWM signal or one PWM signal combined with at least one digital line to drive an H-bridge which would forward/stop/reverse the motors.

Basically, you can use the RC radio PWM signal to transmit speed and direction INFORMATION to an uC which would take this information to know how what drive signals to send to the H-bridge. The uC would need to use MULTIPLE PWM signals (or one PWM with digital lines) to drive the motor in 3 states. You cannot directly drive 3 motor states from a single PWM signal.

There is no way you can design an H-bridge to directly drive a motor in 3-states from a single PWM signal. You need more signals to drive an H-bridge in 3 states. What you can do is use the PWM as radio message to tell the uC how to drive the H-bridge (and it would drive the H-bridge using multiple signals).

I think I basically said the same thing 3 times.