Cheap 3.3V 250mA Power Supply

This is a description of how to build a cheap regulated 3.3V power supply for your projects

  • 3.85V to 13.2V input
  • 3.3V output
  • Max 250 mA out
  • Shortcircuit and thermal protected

It is based on the MCP1702 3.3V Regulator,
which has internal current and thermal limiter.
TO-92 is the name of this kind of component Package (3 legs, flat top).

This is the Circuit we will build:
This Column is the fast track This Column is for extra help

Bend the legs on the TO-92 to fit the board, and insert it in the board
This is how this Solderless Breadboard is connected:


Connect the first 1 uF capacitor between PIN-1 and PIN-2 of the TO-92
The side marked "-" should be towards PIN-1 (Ground).

This is an Aluminium Electrolytic Capacitor
"-" is to the left on this picture
You might need to cut the legs if they differ a lot in length.

Connect the second 1 uF capacitor between PIN-1 and PIN 3
The side marked "-" should be towards PIN-1 (Ground).

Capacitors can look pretty different, but all theese are Polyester Capacitors of 100nF = 0.1 uF capacitance.

Which direction you connect them does not matter for plastic or ceramic capasitors like theese.


Connect the red lead of the Battery Snap to PIN-2 and the black to PIN-1
Tweezers can help here.

Connect PIN-1 to the Ground Rail of the board (Blue or Black). PIN-3 to the VCC Rail (Red)

If you are having trouble with stripping the wires, use a Wire Stripper. :-)
(This is a 4$ model)

Connect this Ground rail to the Ground rail on the other side.
Connect the VCC rails

Test it with a LED

Connect GND through a 100 (to 1k) Ohm resistor, (in this case we use the a 220 Ohm resistor), to the short leg of the LED.
The long leg of the LED to VCC of the board

Connect a 9V battery.
If the LED lights up, you got power.
If not, check that the LED is connected in the right direction. (the long leg towards VCC).


These are the wire lengths I use in my projects.
If you want to use any other powersource, you can connect any DC source with a voltage output in the range between 3.85 and 13.2V instead of the 9V battery.

Just connect Ground to PIN-1 of the Power regulator (TO-92) (row 1, column F)

And + of your power source to PIN-2 = the middle pin on the picture = row 2, column F.

Last modified: Sun Jun 15 01:16:22 Västeuropa, sommartid 2008