Unipolar Microstep Driver Schematic

[Heyme]

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.

Thanks

 

[john jardine]

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.

Thanks

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

 

[Spehro Pefhany]

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

That AC coupling to the darlingtons is interesting...

 

[john jardine]

That AC coupling to the darlingtons is interesting...

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

 

[john jardine]

That AC coupling to the darlingtons is interesting...

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

 

[Heyme]

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?

 

[john jardine]

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?

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.
http://www.piclist.com/images/member/RB-ezy-Q33/circuit.jpg
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]

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.
http://www.piclist.com/images/member/RB-ezy-Q33/circuit.jpg
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

That Roman Black is one cool cat!

 

[Heyme]

That Roman Black is one cool cat!

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.

 

[john jardine]

[...]

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