v108lszu@ubvms.cc.buffalo.edu (03/21/90)
I'm not sure if this is the right newsgroup for this, but...is anyone out there experienced in the use of stepping motors? I've got a couple which I have managed to get working through the use of my parallel port (on my PC clone), which works OK. My question is this: for a given number of steps per revolution and size of motor, how rapid a rotation rate can I reasonably expect? I plan to use the motors in a device in which *both* fine and rapid positioning will be desired. I guess it's kind of a tradeoff between the two, but I really don't know enough about steppers to be sure I'm getting everything out of them that I can. Would the use of a more elaborate (ie, commercial) PC interface allow me to step them faster? I've gotten up to about 20 RPM with a 72 step/rev motor, which seems pretty good so far. Another point is this: I need to control at least two motors at once (possibly three or four) and anything I build to divert the control signals from the parallel port to each motor in turn will no doubt only slow things down! I'd appreciate email from anyone who can shed any light on this subject...if you're interested in telescope mirror making, I'd also like to discuss that as well. That's what I'm aiming for......... Thanks...PF ****************************************************************************** Pat Ferrick/KA2AYK Call me "Ferrick Bueller" only if you must!!! V108LSZU@UBVMSD.cc.buffalo.edu ******************************************************************************
chuck@mitlns.mit.edu (03/22/90)
-Message-Text-Follows- In article <691.2607394d@ubvms.cc.buffalo.edu>, v108lszu@ubvms.cc.buffalo.edu writes... >I'm not sure if this is the right newsgroup for this, but...is anyone out >there experienced in the use of stepping motors? > >I've got a couple which I have managed to get working through the use of >my parallel port (on my PC clone), which works OK. My question is this: for >a given number of steps per revolution and size of motor, how rapid a rotation >rate can I reasonably expect? I plan to use the motors in a device in which >*both* fine and rapid positioning will be desired. I guess it's kind of a >tradeoff between the two, but I really don't know enough about steppers to >be sure I'm getting everything out of them that I can. > >Would the use of a more elaborate (ie, commercial) PC interface allow me to >step them faster? I've gotten up to about 20 RPM with a 72 step/rev motor, >which seems pretty good so far. Another point is this: I need to control at >least two motors at once (possibly three or four) and anything I build to >divert the control signals from the parallel port to each motor in turn will >no doubt only slow things down! > There are several controllers for stepping motors, typically you have a "step" line and a "direction" line so you could handle four motors with your parallel port. Check Motorola and National. The hard part is that to get true high performance stepping you need to take acceleration and load into account. That is you have to step slow until you get moving and then step faster once the motor is moving. If the load is negligible and all you have to do is account for the inertia of the motor this is not too bad, A linear ramp in stepping speed between a empirically determined min and max stepping rate works well. If you have varying loads that is a much tougher problem, probably better handled by a position encoder and some feedback than a stepper where you can loose steps. A question I have: It should be possible by watching the back EMF of a stepper to detect missed steps. Has anybody done this? Chuck Parsons CHUCK@MITLNS.MIT.EDU