Syncronous dc motor

Clark MacDonald (clark@witch.mitra.com)
Mon, 31 Jul 1995 08:55:56 -0400 (EDT)

I have a question about a DC syncronous motor running at a much lower voltage than it was designed for. The motor is designed for 20 VDC for a geared output of 1 rpm. Thanks to this list, I now know that my newly purchased polaris mount needs 1/10 rpm.

This is the question part. I have placed a standard 9 volt battery in line with a 400k pot to trim what the motor sees. The combination will just barely put out the required 1/10 rpm before the motor wishes to quit. I successfully watched M13 for 40 min. last night with no counterweight, for my 4 1/4", and no sign of the battery being exhausted.

Question: Will this battery combination last? (Say for 6 hours). I did find that when I pushed the scope against the RA clutch the motor could not handle the extra stress so it stopped. I had to restart it at a faster speed to restart it again. You should hear this puppy. It sounds like it barely moves at all.

This is probably a temporary measure anyway, but I have never owned a mount that tracks. What a treat.