Connect a lamp cord with plug to the 110-volt side of the transformer. Install an in-line lamp dimmer on the cord. Connect the transformer's low-voltage output in series with a silicon diode and the motor. If the transformer has a third "center tap" output lead (usually marked with a stripe), tape it off and ignore it.
Be sure all connections are well insulated, and all wires have good mechanical strain releif attachment to prevent accidental dislodging. Danger: For personal safety the 110 VAC house current connections must be properly insulated to prevent shock, and strain-releived to prevent accidental dislodging. For operation, plug only into a ground-fault circuit-interrupt protected outlet. Observe your local electrical code.
The silicon diode should probably be mounted to a heat sink (just about any piece of metal will do) so it doesn't overheat. The one illustrated uses a big steel washer for a heat sink.
Note: the 110VAC called out above is nominal for U.S. house current supply. Adjust the values if your supply differs. This circuit provides half-wave rectification, which means the motor will be receiving pulsed direct current, with the pulses arriving 30 times per second (U.S.). If this produces a jerky motion in the motorized revolving Jupiter magnet, consider using a full-wave bridge rectifier instead of the single diode. Both leads from the transformer's low voltage output would attach to the rectifier's "AC input" leads, and both "DC output" leads from the rectifier go to the motor. This will produce a more continuous, although rippled, DC output. A filter capacitor is not required unless the motor is small and sensitive to rippled input (in which case try a 200 µF 50VDC, or higher value, electrolytic capacitor in parallel with the diode's output, and matching its polarity).
If the motor rotates in the wrong direction, reverse its DC connection.
|Component||Spec||Quantity||Typical Source||Approximate Cost|
|Transformer||110 VAC input, 24 VAC @ 1 Amp output||1||C & H Sales, Pasadena, or an electronics store such as Radio Shack||$6.50|
|Silicon Diode||50 VAC, 1 Amp
or higher value
|1||An electronics store such as Radio Shack||$1.00|
|In-line Lamp Dimmer||100 W||1||Hardware store or home-improvement store||$7.00|
|Wire||16-guage lamp cord, with plug for house receptacle||15 ft or 5 m||Hardware store or home-improvement store||$0.50|
|Electrical tape||Vinyl||1 roll||Hardware store or home-improvement store||$0.75|
|Nylon wire ties||Small||10||Hardware store or home-improvement store||$0.50|
|Mounting substrate||Wooden board 3 x 6 inches or 8 x 16 cm||1||Hardware store or home-improvement store||$0.25|