I too have been playing and have completed a PIC based microstepping controller that I will be sharing shortly. I am just finishing up the Visual Basic front end that allows it to be programmed from the computer.
For a DIY project I stayed away from any of the IC based chopper controllers and did everything discreetly. This way I am not bound to a maximum current. If I need more current I just up my FET rating. I am running my hardware on my prototype machine 60 V @ 8Amps. My board supports Unipolar / Bipolar steppers and a Servo motor with and encoder input. I have not played with servos yet but I too read the PIC article. I want to get servos working as well but I am not sure how the STEP/DIR inputs are used with a servo. Do people just actually use the servo like a stepper? A step pulse steps the servo one small increment.
fyffe55 you are right that a small stepper is not good as a position encoder. It is too slow and the output stops when the motor stops moving. I posted earlier about using a small stepper as a jog encoder and in this mode it works great. I use the small stepper motor to replace a mechanical hand crank. Turn the small stepper motor and the axis moves the requested direction. Good for quick manual positioning without a computer connected. You can make a better position encoder by drilling a disc with a hole every 0.9 degrees and using an IR RX/TX pair. The encoder resolution can be increased by using a standard 4X decoding or gearing so the encoder wheel spins faster than the motor or both.
As for the J Kerr board, one thing I learned a long time ago is that inspiration comes from many places and things will be copied if it will make money.  |