On 2010-06-12, Wes wrote:
Ignoramus10537 wrote:

I don't think so. If it was a tach, I believe you would only see two brushes. That is
based on the limited number of servo motors I've had a part. I could be wrong.

I will look a little closer. I thought that the wires were too think
to carry the main motor current. I will try to find out for sure
tonight.

i

Did you resolve it?


Wes, yes, I am 100% certain that it is a tachometer. 9.5 volts per
1000 RPM.

Interesting. The 4 brushes seem like overkill for a tach. I wonder why a two brush
design wasn't good enough. EE's, got an explanation?

My guess is a slight overlap of switching time between two sets
of brushes so one switches while the other makes full contact to
minimize glitches in the feedback signal -- which could cause glitches
in the speed of the motor, and mar the finish of the workpiece.

Enjoy,
DoN.

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