Single Output Supply


This is a simple power supply circuit providing general purpose voltage regulation using the popular LM78xx linear regulators. A power supply module like this is useful for a lot of projects and is easy for beginners to build and understand. The regulators are inexpensive and can also be scavenged if you have a stash of circuit boards from broken electronics. I typically use this to regulate the voltage from a wall wort to power various circuits/projects.

There's not much to understand in this design, it's just a few capacitors to filter the DC input and output from the regulator. A diode prevents damage from reversing the power input connections. If you don't want the diode you can replace it with a jumper wire. This design includes a power switch and power LED to indicate when the circuit is turned on. Several output connections were added to allow the supply to run multiple circuits in a more complex project. Use a small heat sink on the regulator to prevent overheating if you're powering a heavy load.

Completed SOS power supply with 7805 regulator (+5V)

SOS power supply turned on and reading +5V output

SOS power supply turned off and reading 0V output

The switch came from electronic goldmine (G18021B, G18021) in a large quantity. I only needed to buy 150 at the time ($0.05 each) but that particular item doesn't exist anymore.

Eagle Design Files

Cadsoft Eagle pcb schematic [ .PNG | .SCH ]

Cadsoft Eagle pcb layout [ .PNG | .BRD ]


  1. LM78xx series regulators from Fairchild
  2. G18021B, G18021 - switches from Electronic Goldmine