simple speed controlled motor

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Posted by: Jim Pitman (71.169.180.---)

Date: March 05, 2022 05:05AM

<img src="documents" alt="Simple speed controlled DC motor" />
I like to rotate my blanks very slowly while I apply finish to a wrap. I have designed very much more complicated motion control gear in the past but this is a minimalist DC gearmotor/speed controller that is withing the reach of the hobyist and is quiote cheap. The bill of material has only five entries.
6v DC wallwart at 300ma Geared DC motor, 200ma or less, 60RPM at 12V Potentiometer, 10K with screw driver slot shaft 2N3904 NPN transistor&nbsp; small peice of perf board or phenolic to mount transistor and pot
The schematic is quite simple. The transistor is configured as an emitter follower, voltage regulator. With DC motors, speed is propotional to voltage for the most part. The transistor buffers the pot output voltage. I can get a very slow speed with this arangement or 30 RPM max.

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