Pocket Power Supply Kit

Skill Level: Beginner
Assembly Time: 2-3 hours  

Pocket Power Supply Kit This is a pocket sized power supply with a 9 volt input and a selectable output voltage. The output can be set in 1.5 volt intervals (1.5, 3, 4.5, 6) to mimic one to four 1.5V batteries. This little supply can be used at garage sales, flea markets and thrift stores to test electronics before you buy them.

Required tools and parts:

Soldering Iron & Solder
Phillips screw driver
Drill & drill bits
Wire cutters
Computer with a printer (to print cutout template)
(1) IC, LM317T, TO-220 (U1)
(10) Radial capacitor, 0.1µF, 50V (C1)
(10) Radial capacitor, 1µF, 50V (C2)
(10) Resistor, 1/4 watt, 220Ω (R1)
(10) Resistor, 1/4 watt, 56Ω (R2)
(10) Resistor, 1/4 watt, 270Ω (R3, R4, R5)
(10) Resistor, 1/4 watt, 560Ω (R6)
(1) DIP switch, SPST, 4-position (SW1)
(1) Battery snaps, M/F pair, PCB mount (J1, J2)
(1) Alligator clip test leads, 2pk
(1) Plastic case, 3.2" x 1.6" x 0.8"
(10) LED, red diffused, 2.1V (D1)
PCB Board

Step 1 - Review the Schematic


Step 2 - Loading the Circuit Board

Install the components as shown in the table and schematic above. Completely solder the capacitors, resistors and voltage regulator first. Then cut all of the leads so they are as flush as possible to the board. Next install the DIP switch, LED and battery connectors. R6 and D1 are optional if you want to have a “power on” indicator. Finally cut the alligator clip wires to the desired length, strip the ends and solder them to the board.

Loading the Circuit Board

Step 3 - The Enclosure

First, print the cutouts.pdf to scale and cutout the board template. Break off the small standoff on one side of the box. Insert the paper template into this end of the box and use it to mark the cutout locations. Many tools can be used to create the cutouts. I drilled the LED hole and the four corners on the DIP switch hole. Then I used a dremel tool to open the square up. Last I used a flat needle file to fine tune and smooth the opening.

The Enclosure

Step 4 - Put it All Together

Attach a 9 volt battery to the connector. The assembly should slide into the box and wedge into place. Now decide where you want the wires to exit the enclosure and cut two small slots for them. Install the back plate and screws.

Pocket Power Supply

Step 5 - Operation

Switch one turns the circuit on/off

Pocket Power Supply