The Simplest, Cheapest 3.3V Power Supply in the Universe

With so many 3.3V devices around now I decided to build a cheap and simple little 3.3V supply for breadboard prototypes. This supply is dead simple to make and only took about 25 minutes to build start to finish.

I always seem to need power supplies for things and didn't want to build a complete power supply and pay $25 just for the transformer again! So in order to save money we'll try repurpose an old cell phone charger from the junk box which is essentially free.

Here I try out old Samsung and Apple chargers which both worked with an approximate 500 ma load. That's about the maximum that I'll be using on a breadboard but both devices are rated to 1 amp if you need it. If you need a lot of current you may need to heatsink the regulator. At low currents you can get by without a heatsink.

In the end I used an old Samsung charger because the wires were thicker and more robust (and there's no possibility that it will ever be used with a 10 year old cell phone again!)

Supplies

1 - scrap of vector board
1 - LD33V (L1117) voltage regulator
1 - Surplus 5V cell phone charger with up to 1A capacity
1 - 0.1uF capacitor
1 - 10uF capacitor
1 - 220 ohm resistor
1 - LED
2 - Jumper wires
Solder
About 25 minutes of time

Step 1: Circuit Diagram

The circuit is dead simple. Just connect the cell phone charger to the voltage regulator input and get 3.3V from the output. You should include the filter caps on the input and output, but you could get away with leaving them out. An indicator LED is optional too.

Step 2: Breadboard It If You Are New to Electronics

If you are new to electronics, you may want to build the circuit on a breadboard first just so that you are confident about how to hook it up before committing to the permanent build.