From: Lou Boyd
Subject: Re: 3 wire stepper motors
Date: Thu, 26 Sep 2002 21:15:54 -0700
Organization: The University of Arizona
NNTP-Posting-Date: Fri, 27 Sep 2002 04:15:55 +0000 (UTC)
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David L. Peterson wrote:
> On 26 Sep 2002 03:57:18 -0700, firstname.lastname@example.org (Ralph Seguin)
>>I noticed at a surplus shop some Superior Electric NEMA 34 stepper
>>motors, 120V, 0.3A, 50 oz-in, 3 wire.
>>What is a 3 wire stepper motor?
>>How does one drive them?
>>I have a really small budget ($0 if you ask my wife :-), so I don't
>>think I can afford all the nice servo and stepper stuff.
>>I have a 3 axis stage with 10 TPI Acme screws on X and Y and a
>>ballscrew on Z that I'd like to make into a little mini-CNC mill.
>>I know that 50 oz-in is pretty low compared to some of the 150-250
>>oz-in motors that I've seen, but those other motors are pricey.
>>I was thinking of rectifying 120V AC to 120V DC and using that as a
>>power source, or maybe rectifying 240V AC to DC. Is this a bad idea?
>>Are these motors worth investigating, or should I save my pennies?
>>Inexpensive source for kick ass motors, drives, controllers, ...? :-)
>>Inexpensive source for power FETs?
>>Inexpensive source for rectifiers?
>>Inexpensive source for power diodes?
>>rpseguin AT yahoo DOT com
> I have a bigger superior electric 3 wire stepper motor (it's laying in
> pieces by my feet right now) that I took apart a few weeks ago to see
> if I could turn it into a regular stepper motor. After tracing out
> the circuit board soldiered to all the coils I have to say that, yes,
> they can be made into regular bipolar/unipolar motors relatively
> easily. Is it worth it for a 50oz-in motor? Not for me, the one I
> got is a 720 oz-in so I was thinking about it. :) If you have a
> soldiering iron, and exacto blade, and some scraps of wire you can
> make them into regular six wire steppers pretty easily. Looks like
> you could ditch the circuit board completely and rewire the coils in
> parallel to make it run on half the voltage, but that's take a lot of
> patience and a pretty good understanding of what you are doing.
While these look like steppers they are actually synchronous AC motors.
They can be driven as steppers, but it takes a rather high voltage
driver capable of putting out positive and negative voltage in
quadrature. Surplus stepper are pretty reasonable in price so converting
these motors to 4 or 6 wire is generally not worth the bother
considering you'll still need a high voltage driver.