Unipolar Microstep Driver Schematic

I am looking for a simple microstep motor controller to drive a 5 wire unipolar stepper motor (4 phase wires, 1 commmon). The stepper draws less than .5 amps at 24VDC. I prefer a stand alone solution with a trim pot for speed control, with the posiblility of adding a couple switches to select a high speed, low speed and reverse.

Using a PIC uC is a posibility, but maybe a bigger time investment than I have right now.

Any ideas? Any good sites to check out. I've been googling for a couple of days now and seen many kits, but not much in the way of a schematics, or suggestions.

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Goto Google, "Images" and type "stepper unipolar" (no quotes). Look at the first drawing. regards john

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It was the "GIF version #1" I was looking at (sans caps). God knows why he's put the cap's in the Gif version #2 ???. Sod it, I'll go back and read the words. regards john

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Yeah ... makes sense ... Detent holding etc ... Never thought anyone would want a battery operated stepper!. regards john

Well that is basically the full step circuit that I have started with. Found something similar on a different web site that still uses the 194 chip, but uses 2003 darlington drivers. Anyhow that is a very nice standalone full step circuit that I have currently built and using, but I need finer steps and smoother operation. Any other suggestions? I found the linistepper on piclist. Anyone have experience with this kit?

That Roman Black is one cool cat! :)

Apologies!. Missed the "microstep" item. I whinge about it yet do it myself. Yes. The 'Linistepper' is also the only bookmark I had that offers simple microstepping.

Looks perfectly OK and with a kit at a reasonable price, (if progging a PIC is a problem). Yes, microsteps do give much smoother and quieter motor running, especially noticable if the motor has been solidly bolted to metalwork. You'll need an external 'step' generator and pot' (eg simple 555 oscillator or '4093) and the current limiting resistors changing for your

24V motor (say 2ohms). regards john

Mark Jones wrote in news:QLqdnV4r8 snipped-for-privacy@buckeye-express.com:

I agree that it seems like a nice circuit. The only real question I have is that he talks about a slow stepper speed of less than 5 revs per second. My system will be more like 4 rpm. Do you forsee any issues with this. (200 step per rev motor * 4rpm ) running less than 13 full pulses per second.

My, my! what a lot of reading needed doing to find that suggested-speed paragraph. Seemingly reams of irrelevant details but sod all in the way of performance figures or overviews. I'll just have to make an assumption that the unit works as a commercial microstep unit would. In that case a single "step" input should move the motor a single full step, down to a single (tiny) 1/18th step. The step amount being set by the 2 "mode" pins. So, 4 revs a minute could be obtained by linking the mode pins for finest movement and sending 18 * 200 * 4 = 14400 steps per minute or 240 pulses per second to the unit. Unfortunately the 240pps step rate is still quite low and you'll feel 'em and hear 'em. So yes, there could be an issue. But ... If you tune-up those ramping caps to like say 1000uF, the microsteps could be a lot smoother. (Anyway it's all guesswork on my part, so don't quote me :-) regards john