Dual voltage regulated power supply for Arduino/microcontroller projects

Picture of Dual voltage regulated power supply for Arduino/microcontroller projects
About a couple of months ago when I first had my hands on Arduino Uno, I had no idea where does that 3.3V power next to the 5V pin comes from, or more accurately, I did not really think about it until I had to make my own versions of standalone Arduinos/ATmega projects. I needed 3.3V source in addition to the regular 5V for driving some of the components. I soon realized that ATmega microcontroller does not provide a 3.3V output from any of its pins as a dedicated power source, I must create it through power circuit design. So here is my humble design. There are tons of similar materials available on the Internet. I read many of them and the datasheets, and put my understanding together in my own way, to suit my own purpose. I am sharing it here in a hope that someone as novice as myself can perhaps use it readily.

Step 1: Material needed

Picture of Material needed
1) Strip board, I took a 24 strip board
2) 1 Terminal block (I took a screw terminal)
3) 1 Switch
4) 3 Electrolytic capacitors (recommended two 10uF and one 1uF, but I have used all 10uF)
5) 2 Resistors (R1 & R2, where the R2/R1 ratio should be nearly 1.64. I have used R1=1k and R2=1.5k instead of 1.64k. This is why I shall get 3.13V, not 3.3V. You can use a calculator like this)
6) 2 pin Male header (optional)
7) LM7805 5V voltage regulator IC
8) LM317 3.3V voltage regulator IC
Fearce11 year ago

These two regulators usually go hand and hand with me and are a necessity for tons of (Arduino included) circuits.

Good job with the strip board combo Nice neat & compact.

I would like to reference this video for help to others.


Sayedur (author)  Fearce11 year ago

Thank you Fearce1 for complements and also for the video link :)

pfred21 year ago
If you make R2 an adjustable trimpot you can get the exact voltage you want.
Sayedur (author)  pfred21 year ago
Oh yes, I have seen people suggesting use of pot for accurate adjustment, and variable output. I first thought I would give that a try, then backed out for apparently nothing :D Thanks pfred2.
pfred2 Sayedur1 year ago
The common value to use is a 5K potentiometer. If you get a 10 turn trimpot then you do not have to worry about it coming out of adjustment on your either. I used 10 turn trimmers on this:

Nicely done. A well documented and thought out project. Congratulations.
Sayedur (author)  cobourgdave1 year ago
Thank you very much for encouragement.