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!

Step 1: The Parts

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!

Step 2: The Variable Voltage Regulator.

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

Step 3: Adding the Digital Readout

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

Step 4: You're Done

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