12V Unregulated Power Supply

Car windshield wiper motors are very useful for motor driven props. They are powerful, relatively quiet, usually have two or three speeds, are easily available and inexpensive. The problem comes in powering the motor. Wiper motors can draw a lot of current and few easily available AC to DC power supplies can provide the needed amperage. The solution is usually to use a car battery charger or hack a computer power supply. Chargers can be expensive and computer power supplies can be a challenge to get running, in both cases the power supplies are often bulky and take a lot of room. An alterative is to build your own power supply. Wiper motors require lots of power but they don't need particularly well regulated power, this makes it much simpler to build a suitable power supply. The following circuit will supply sufficient power to run the motor under most circumstances. It should be noted that while we have used this supply successfully it has never been used with a continuously operating motor. If used continuously heating may become a factor. A few other downsides to note are that transformers of this size can be rather expensive and since the supply is unregulated it should not be used to power other electronics.

Part #	Part Name	Supplier
T1	115:12 VAC 8 A Transformer	Surplus Center
BR1	Bridge Rectifier	Jameco
C1	1000µF 25V Electrolytic Capacitor	Jameco
SW1	SPST Switch
F1	10A Fuse