Key Chain USB Power Supply (For Bread Board Projects)

Hi everyone ,

In this instructable, i am gonna share with you how i made these simple key chain USB power supplies that gives separate outputs from 1 to 5 V DC.

These can be used for bread board experiments that need low voltage dc supplies.

This simple project needs a few things.

1. Copper clad board.
2. Old key chain.
3. AS 1117 voltage regulator (3.3 V).
4. 100 Ohms resistors (SMD).
5. Stacking header pins (male).

We are gonna make two key chain power supplies.

One gives 1 to 5 VDC output and the other gives 5 and 3.3 vDC output.

The first one "circuit 1" is nothing but a voltage divider network connected between the +5 and Gnd terminals of the USB output.The voltage divider is designed using five 100 Ohms resistances in series so that each one can have 1 Volt across it. SO, if we need 2 V, then take output across any two of the series resistors. And so we may take 1,2,3,4 and 5 V DC output.

The second circuit, "circuit 2" gives two voltage outputs, 5 and 3.3 V DC. We use AS 1117 smd 3.3 v voltage regulator in this circuit.

1. Cut the two pieces of copper clad board as per the picture and to fit the usb port (in the shape of a pen drive).
2. Draw the layout diagram of the circuits on the board (as per the circuit diagram).
3. Carry out the etching using ferric chloride.

• Solder the smd components carefully.
• Solder the connectors.

• glue a small piece of pcb at the end to make the thickness enough to fit the usb port.
• drill hole to connect the key chain.
• put everything together.