Stepper Skipping Steps

[skartch]

I'm new to the stepper motor world and I have a few questions. I work in electronics and I have access to lots of parts, so I built a controller/driver circuit using parts we have in stock. My stepper says it is rated at 5 Volts and 1 Amp. Measuring the winding they do indeed come out to be 5 Ohms. Right now I'm just experimenting, I have a variable frequency clock driving my circuit and I have an up/down switch so I can run it in either direction. Everything is working great at extremely low frequencies but after I get the clock up around 400 Hz I can tell that it starts skipping steps and if I go higher it will stop and just buzz not rotating at all. I looked up the specs of my motor on the web and each phase/winding (4 in all) has 8 mH of inductance. So with a little math, I find that the cut off frequency(where the inductive reaction equals the winding resistance) is 99.47 Hz. So it looks like I'm going to have to run the clock at less than 400 Hz. What bothers me is that the motor rotates 1.8 degrees per clock pulse and requires 200 pulses to make one revolution. That means that the fastest that I can run this is 2 turns per second. If that is driving a 18 tpi actuator it would take 9 seconds to move 1 inch. Am I missing something here? Are the CNC's really that slow? Is it my motor? I am switching only 5 volts and I could run a higher Voltage with a resistor or better yet a one amp constant current source to try to overcome the inductance. Does anybody have any experience with this? How fast are you guys rotating your motors? Any thoughts would be greatly appreciated.

Thanks

Steve

[vger]

Is your motor connected to anything while testing? Could be you are seeing mechanical resonance causing the issue. Try attaching a load to it, or just a sizable flywheel and repeat the test.

Steve

[budP]

If I understand right you are trying to run your motors on 5volts, you need to run these motors on at least 24 volts
budP