A rechargeable, pocket-sized 5-volt power supply

Use this compact component to power anything that needs juice in your DIY projects.
A homemade 5-volt power supply.

The finished power supply. Dave Prochnow

Sure power supply projects aren’t that sexy; but they are, generally speaking, the foundation for every electronics project. The voltage output for this project is 5VDC, and a practical output that can be applied to a wide variety of digital components.

Even better, this power supply has a two-pin plug that can be quickly and easily snapped into a common two-pin header for a reliable and solid power connection. Add a pushbutton on-off switch and a USB rechargeable interface and you have a versatile power supply that can be slipped inside your pocket.

Note: In the coming weeks, I’ll build a project that converts a 12-volt AVR Development Board into a 5-volt “candy bar” computer using this power supply.


  • Time: 2 hours
  • Cost: $47.63 (excluding tax and shipping charges)
  • Difficulty: easy



1. Remove the 5-volt barrel power connector from the LiPoly charger.

2. Temporarily install the LiPoly charger inside the project box. Mark the location for the USB port. Remove the charger and cut a hole in the side of the box at this marked location.

3. Mark the location for the SPST switch. Drill a 3/8-inch hole for the switch and install the switch. Drill two holes in the side of the box for enabling access for the external power wires (i.e., + & GND). Finally, drill ventilation holes in the box lid. These ventilation holes also enable you to “read” the LiPoly charger’s status indicator LED while recharging the battery.

4. Assemble the 5-volt DC-to-DC step up PCB, polymer lithium ion battery, LiPoly charger, SPST switch, and hookup wiring per the SparkFun Electronics’ product datasheets.

5. Carefully tuck everything inside the box. Insulate all exposed metal surfaces. Screw one corner of the LiPoly charger into one of the box’s internal PCB standoffs.

Inside a homemade 5-volt power supply.
Inside the box. Dave Prochnow

6. Attach two Amp contacts to the external power wires and insert the contacts into the two-pin housing. Test your wiring and SPST switch operation with a multimeter. Recharge the battery via an open PC USB port. Remove the USB cable, press the SPST switch and make sure that the external power wires are receiving 5VDC. Button ‘er up; you’re done.

Enjoy your new 5-volt rechargeable, pocket-sized power supply.