Re: [CAD_CAM_EDM_DRO] Sevo and Encoder identifying

> I'm just working out what servos to use with some Gecko 340s,
> I have a few old ones lying around which might be a start, however
> the jumble of leads on them is putting me off trying any.
>
> How do I tell if a motor is brush or brushless, ie. suitable for
> using with a Geckdrive ?

Well some clues would be brush caps on the outside of the motor, only
having two wires (though that is not the case with all brush motors),
etc. If you find a likely-looking candidate, use a 6v lantern battery
or a bench supply to put a low voltage on it and see if it spins. Or
chuck it in a lathe and spin it, while measuring the voltage on the
leads.

> How would I identify the different leads emerging from an encoder, I
> have an oscilloscope, but am not skilled in using it.

Try to look for clues on the carrier pc board if any, or the wiring
harness. thick leads are probably power - and if one of those is
doubled it is likely ground. If there is a small capacitor across two
leads, those are probably the power ones. Then get it spinning and
look at the remaining leads with the scope - you are looking for two
square waves that are 90 degree out of phase. If you find two that
are 180 degrees out of phase (ie, opposites) you have a differential
pair of outputs for one phase signal. Grab one of those wires, then
continue looking for one from the other phase. (the Gecko's only need
single-ended encoders - either side of a differential pair should do).
If you don't like the rotation 'sense' of the encoder, simply swap the
two wires. See if there are any part numbers or manufacturer names on
the encoder to act as a clues to finding further information.

Chris

-------------------------------------------------
Christopher C. Stratton
Engineer, Instrument Maker, and Horn Player
ccs@... 617 628 1062
http://web.mit.edu/~stratton/www/brassbuild.html