Re: Q's for the stepper experts.

Donald,

Most of the older 5V,1A motors are really about 50 oz. inches.

Six wire motors cannot be wired in "parallel". They consist of two
center tapped windings. So you can run from one end to the center tap
on each coil(which is what I suggest, unless you are moving SLOWLY);
or you can "use the whole winding" and run from end to end, ignoring
the center taps (Mariss has posted recently on the particualrs of
this).

Run your voltage as high as you can ,given the drives you are using.
What I'm about to say is a gross oversimplification, but I'll say it
anyway: With steppers, volts equal speed, and amps equal torque.

These motors were designed for a unipolar drive originally, and have
a relatively high inductance.

Inductance? Think of a pail of water with a hole in the bottom. You
can only keep adding water to the pail as fast as it is flowing out
the hole in the bottom. High inductance motors have a small hole in
the bottom of the pail; low inductance motors have a big hole.

(lower inductance motors will have low volts/high amps ratings
typically) This means you want as much volts as possible to "push"
the electrons into the coil...

Continuing the analogy above:
This is like putting a cover on the pail, and screwing a hose fitting
to it. Now we can "force" the water into the pail a little faster
than we could when the pail was uncovered; but we are still limited
by the size of the hole in the bottom!

So for a given motor inductance (size of hole in the pail bottom),
there will be a "top speed" for each voltage, since voltage is
the "pushing part" of electricity. Also called electromotive force.
Now you know why they use an E for volts!

Some have said it takes a 2 amp supply (per motor) capacity. This is
not the case with chopper drives! While you won't go wrong with an
8amp supply, you can probably get by with 5A. I tend to go a little
high on the filter cap mfd's, compared to some I've seen.

I've used SCADS of these motors at 34V with an SGS 297-298 driver (2A
bipolar).

Hope this helps.

Ballendo

--- In CAD_CAM_EDM_DRO@y..., "Donald Brock" <don.pat.brock@p...>
wrote:

> Hello group,
>
> I have a question for those who understand the nature of the beast.

My

> reading has left me a bit confused and maybe some of you can set me
> straight.
>
> First the background. I have four (older but new) Astrosyn 5V 1A 70-

80 oz.

> in. steppers I want to drive in bipolar mode for a home built

engraver (no

> milling) I have not been able to find data on these older

(designation)

> astrosyns. They will be pushing 1/2"-10 Acme screws except for a

forth axis

> which will come later on if all works out. The current rating from

what I

> understand is usually given for the unipolar rating with the

bipolar rating

> being at 70% of this (got that from some compumotor data). Please

correct me

> if this is wrong.
>
> Now with that said, I also see in some of this compumotor

literature that

> the windings of these six wire steppers can be run in series or in

parallel.

>
> Series hook-up being:
> 1A - Red
> 1B - Red/Wh
> 2A - Grn
> 2B - Grn/Wh
> NC - Wh, Blk
>
> Parallel hook-up being:
> 1A - Red
> 1B - Blk
> 2A - Grn
> 2B -Wh
> NC - Red/Wh, Grn/Wh
>
> I'm assuming to run with a bipolar chopper drive I would want to

run with a

> series connection. Is this a correct assumption? If so what current

limit

> setting should I be using using on each drive for each motor if the

above is

> incorrect?
>
> My next question is has to do with the (up to) 2A drives I'm

looking at.

> They will take a 12VDC to 18VDC source for the motors.
>
> What voltage/current for my power supply should I be looking at to

drive all

> 4 of these motors with a 5V tap off of the main supply?
>
> I want to give thanks in advance for all replies,
>
> Donald Brock