Re: [CAD_CAM_EDM_DRO] Stepper NG??

If you don't have a test equipment that can measure resistances below
2 ohms within say +/- 20%, you might get a flashlight battery or two
and simply try applying voltage to the wires in pairs. When you find
a phase the rotor will either turn a tiny bit, or at least cog more
strongly than usually.

DO NOT USE NICADS for this kind of test. They have too low an
internal resistance and can deliver scary currents. Instead, get the
cheap (non-alkaline) disposable kind.

Incidentally, are you sure that this is a stepper motor? Might it be
some other kind of motor, an AC synchronous motor (electrically
similar to stepper, but higher resistance) or even some sort of
encoder or resolver? If the resistances are >1k I would guess it is
an AC synchronous motor, as 120v^2/1kohm = 14.4 watts.

Chris

> Alan,
>
> Don't know what it is, I'd assumed bipolar. It's an 8 wire with two sets
> of wires soldered together, so I'm assuming it's series wired.
> Was trying to confirm that when I discovered that every wire seems to
> show continuity to every other wire and ground! I'm using a Fluke meter
> I bought on eBay, so I can't vouch that it's OK. In fact, either
> something really screwy is up with the motor or the meter is bad. I went
> back to get some readings to post, and I got totally different readings
> than the first time. With the scale set to 200k ohms, I see readings
> that wander significantly, like from 1600 to 1800. Be nice to have a
> manual so I'd know what I'm doing with the meter. Or a plain old needle
> type.
> Don't think I'm going to risk an expensive Compumotor driver on this
> sucker. I've got some light duty 34 frame motors I can use until I sort
> this motor out or replace it. I really wanted to use it though, it
> appears to be a double stack, and is fitted with a brake which would be
> nice. At a 4:1 ratio, the dividing head can be back-driven...
>
> Jon
>
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--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
22 Adrian Street, Somerville, MA 02143
http://www.mdc.net/~stratton
NEW PHONE NUMBER: (617) 628-1062 home, 253-2606 MIT