piclist 1999\08\16\141144a >
Thread: Driving a Stepper
www.piclist.com/techref/io/steppers.htm?key=stepper
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face BY : Mark Willis email (remove spam text)



Paul B. Webster VK2BZC wrote:
>
> You didn't reply to the *other* guy's comment on feeding the cats!

 Did, just in private;  I was even polite <G>  I can deal with verbal
humor, just don't physically harass cats or dogs (or people), in my
presence <G>  You should hear the humor that people on Search & Rescue
teams descend to, after 7 days of searching for someone who "Hadta get
there now", was begged not to fly into a bad storm, and flew anyways -
and never made it.  I've heard FAR worse, guys!

{Quote hidden}

 I was thinking Sqrt(2) gain in torque, roughly, if you energize 2
adjacent windings?

> >> I'm sure you have *plenty* of spare plugs on the end of RD-BK-BK-YL
> >> leads!
> >   "Never enough", despite the dozen spare power supplies in the garage
>
>   It appears you, like me, can't bear to scrap equipment even when
> busted!

 I use old connectors to make my own power Y-connectors, and STILL get
stuck for buying more Y-connectors from computergate.com etc., dangit!
Lots of machines here with lots of drives onboard <G>

> > Given the 5 wires (instead of 6), I remembered all that, summat
> > vaguely but well enough as I've been watching the discussions in here.
>
>   5 and 6-wire units are almost identical, except that a 6-wire can be
> used as either a 5-wire or a 4iwire :-).

 No comprendo how you get 4 wires out of a 6 wire unit?  Unless you
drive it with bipolar drivers & use the diodes to bypass half the coil,
is that the trick here?

> >> A diode should be connected across each coil winding. The Anodes
> >> all connect to the Common wire, and the Cathodes connect to A B C
> >> and D.
> > AKA inductive kicks, yep.  OK, makes sense.
>
>   If we're getting particular here, the diodes do *not* go to the
> common, but to common via a Zener or resistor.

 Whimper <G>  Seems people are always arguing this one, if via a
resistor or Zener, how do you do the 6-wires to 4-wires trick?  Why does
"Jones on Stepping Motors" etc. have diodes across the coils?  Or to Vcc
and Ground, depending on coil type.  Maybe it's a per winding type
thing, this all is a lot of good info to re-load on <G>

>  >I need a known speed motor control to spin a little cylinder or disk
> > at a very high, controlled speed, for playing with a Nipkow heads-up
> > display design for wearable computers.  Need something like a 30+ Hz
> > refresh rate for that, want some other motor then <G>
>
>   The complete assembly is available disposals from laser printer
> mechanisms.  Including electronics, though that may be a challenge.
>
>   The capstan assembly from a Hard Disk Drive is an alternative.

 Lasers, I wish I had a spare, could seriously use 48 or 64 LED's at
1/300th inch spacing (That, with a 10-aperture Nipkow disk, would give
me a nice HUD I could afford easily...)

 Aah, old HDD motor, now that's a good thought.  Take an old 2.5"
40-megger or something & make it far more useful <G>  Going to have to
balance torque out, or just assume that things get weird when you move
while computing...

>   And yes, if you have to go *buy* a stepper driver, the L293D is the
> way to go as it is created for the job.  I'm miffed, they were available
> once disposals but snapped up before I could get my order in.

 Happens, darnit.  With me, I usually see a sale, then after they're
gone, find I should've bought 'em all <G>  We'll all cope.  I've seen
them for $3ish, recently.

>   Cheers,
>         Paul B.

 Mark

<37B85453.317ED8E0@nwlink.com> 7bit

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