Power Supply

When working with electronics, you always need one basic thing; power. This power supply is great for powering all kinds of electronic projects. It produces a well filtered, variable 1.2-30 volts at 5 amps. It is easy to build and the parts are realitively easy to find.

Schematic

Parts

Part Total Qty. Description Substitutions C1 1 14000uF or 10000uf 40 VDC Electrolytic Capacitor C2 1 100uF 50Vdc Electrolytic Capacitor C3 1 0.1uF Disc Capacitor C4 1 0.01uF Disc Capacitor R1 1 5K Pot R2 1 240 Ohm 1/4 W Resistor See Notes U1 1 LM338K 1.2 to 30 Volt 5 Amp Regulator BR1 1 10 Amp 50 PIV Bridge Rectifier T1 1 24 V 5 Amp Transformer S1 1 SPST Toggle Switch MISC 1 Wire, Line Cord, Case, Binding Posts (for output)

Notes

1. The regulator comes in a TO-3 case and MUST be used with a LARGE heatsink. You may want to mount a small fan to blow air across the regulator (I did).
2. The filter capacitor is large. It won't fit on any board so bolt it to the case.
3. You can, of course, add a volt and amp meter.
4. Since this project operates from 120 VAC, you must include a fuse and build the project in a case.
5. R2 may need to be decreased to 120 Ohm if you experience voltage drift at light loads. 240 Ohm may not load the output appropriately on some regulators. The datasheet for the LM338K does specify 120 Ohm (I suggest you use a 1/2W unit) so you may just want to use 120 Ohm and not bother with the 240 Ohm resistor showin the parts list. This has been discussed on the forum.