Instructables

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.
 
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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

Step 2: Design

Picture of Design
Here goes my strip board design showing placement of the components. On the right hand side of the picture I have included a strip board friendly schematic diagram, and the actual aerial photograph after assembly.
Fearce14 months 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.

Fearce1 Fearce14 months ago

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

https://www.youtube.com/watch?v=IjJWWGPjc-w

Sayedur (author)  Fearce14 months ago

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

pfred29 months ago
If you make R2 an adjustable trimpot you can get the exact voltage you want.
Sayedur (author)  pfred29 months 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 Sayedur9 months 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:

http://www.instructables.com/id/Dual-POS-NEG-Power-Supply/
cobourgdave9 months ago
Nicely done. A well documented and thought out project. Congratulations.
Sayedur (author)  cobourgdave9 months ago
Thank you very much for encouragement.