Re: [CAD_CAM_EDM_DRO] Digest Number 3422

Message: 8
Date: Sat, 18 Oct 2003 23:24:09 -0000
From: "caudlet" <info@...>
Subject: Re: Testing servos

--- In CAD_CAM_EDM_DRO@yahoogroups.com, GRautoHP@a... wrote:

>> Is there any safe way to test my servo motors to make sure there
>
>
good??????

>>
>>
>
>
Assuming they are brushed DC servo motors, you can just apply DC from
a bench top supply or from a fused source of less than the rated
nameplate voltage. Reverse the leads and the motor will spin the
opposite direction. Let them run for a few minutes and listen for
any skips or strange new noises. Last thing is run an ohmmeter check
between each winding leg and the case to check for shorts. That
should take care of the motors themselves.

If they have encoders you will have to have access to an o-scope and
hook up +5 volts to the proper leads on the encoder (normally +5 is
Red and Neg 5 is Black). By rotating the shaft very carefully you
can watch the logic transitions on the scope.



Could the change be noticed on a DMM or an old Simpson linear meter ???
I have several around here but no longer have access to a scope .

Ron K



Most likely if you get
transitions on each channel the the encoder is okay. If you can get
access to a dual channel scope you can check both A and B channels at
the same time and see the quadrature transitions. .

If you are handy with electronics you can breadboard up a quick 555
pulse circuit for the step (check the achieves for circuit reference
and the files section for actual schematics) and use one of your
motor drive modules to bench test the motor. Depending on the motor
drive circuit you may need to provide a separate +5 power source for
the step and direction common.

If you are using brushless or AC servo motors its not as easy. Don't
apply DC to those type of motors.

Happy building!





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