Variable DC Power Supply for <$15

Variable DC power supplies are critical to many electronics projects. You'll never have to go out and buy dozens of different single-voltage power supplies or battery configurations with this new unit. Professional units can cost hundreds of dollars, but now you can make one for less than $15!

These are the parts you will need:

• LM317 Voltage Regulator ($0.50)
• 0.1 uf Mylar Cap (~$0.10)
• 1 Axial Electrolytic Cap (~$0.20)
• 220 Ohm Resistor (~$0.05)
• 5K Potentiometer ($1.00)
• Cheap Voltmeter ($7.95)
• Enclosure ($1.65)
• Power Supply ($2.85)

Total Cost: $14.30
Not bad for a homemade variable DC power supply!

Start by making the variable voltage regulator. Refer to the schematics below.

Adding the digital readout is really simple! Just open up your multimeter and solder your output to the test leads. Add a switch to the battery. And that's it! You're done :D

Test it and have fun! Put it in an awesome enclosure like I did to impress your friends :)