Feb 19, 2013


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. 


Total Qty.
C1114000uF or 10000uf 40 VDC Electrolytic Capacitor
C21100uF 50Vdc Electrolytic Capacitor
C310.1uF Disc Capacitor
C410.01uF Disc Capacitor
R115K Pot
R21240 Ohm 1/4 W ResistorSee Notes
U11LM338K 1.2 to 30 Volt 5 Amp Regulator
BR1110 Amp 50 PIV Bridge Rectifier
T1124 V 5 Amp Transformer
S11SPST Toggle Switch
MISC1Wire, Line Cord, Case, Binding Posts (for output)


  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.

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