Astronomy Boy: Stepper Motors

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Stepper Motors

Unipolar Stepper Motor – $20 each; two for $35; four for $65, including shipping in U.S.

Brand New Stepper Motors!

I've sold all of the stepper motors, and I do not expect to receive any more. Thanks to all who ordered.

Factory new, unused unipolar stepper motors. Heavy duty motors, ideal for telescope drives and barn door trackers. Work beautifully with 12-volt electronics. Perfect for Mel Bartels' computerized drives!

$20 each; two for $35; four for $65, including shipping in U.S.

Specifications:: Shinano Kenshi, Model STH-55D203-02; Step Angle: 1.8 degrees; 200 steps/revolution; 4 phase; 5.1 VDC/phase; Current per Phase: 1.0 Amp; Holding torque: 59.7 oz/in minimum; Pull-in torque @ 10pps: 34.7 oz/in minimum; Detent torque: 3.1 oz/in; 6 leads, 12.6" long; Size 23 (2.22" diameter; 2.22" Square Flange); Mounting Holes: .20" diameter, 1.856" centers; Shaft: .25" diameter x .75" long; Weight: 1 pound

Stepper Motor Drive Circuits and Controllers
Everything I know about controlling stepper motors, I learned on the web. I have built two control circuits, one for my barn door tracker and one for the RA axis of my CG-5 equatorial mount. Both of my circuits are based on the one found at Ray Grover's A Quartz Controlled Scotch Mount page.

The Godfather of computer-controlled motorized telescopes is Mel Bartels. His site is loaded with information about stepper motors, and he sells a two-axis stepper controller board that you can interface with your PC. Mel told me the motors I am offering are "perfect" for use with his controller. See Mel's Motorize Your Telescope page.

Another useful site is David Rowe's Dual Axis Stepper Motor Controller. This is a standalone controller that does not require connection to a PC.

There is a very simple circuit at the Barn Door Tracker site.

For some theory on stepper motor operation, visit Jones on Stepping Motors.

Finally, a source of stepper motor controller boards priced as low as $5 is a small company called WZ Micro. I've purchased some parts from them, but have not used any of their boards.