I'm currently working on a custom Arduino project where I want to employ the Arduino Uno's ATMega328PU MCU without the Arduino board itself. A 9V battery is going to power my project in the future. Therefore, I needed a compact power supply that allows me to convert the 9V coming from the battery to 5V that the Arduino's MCU requires.

The diode protects the circuit from damage when connecting the battery the wrong way around. The top layer is not necessary, but it helps the 7805 to dissipate heat and keep the circuit cool. For that reason, I added an exclude region around the regulator to ensure that the heatsink makes proper contact with the PCB. You can either solder the heatsink to the top layer of the PCB (as I did) or add a thermal compound and a screw to hold the regulator in place.

Furthermore, the PCB is roughly the same size as a standard 9V battery. Other than that, there's not much more to say. It's a simple circuit, but maybe it helps you in your projects! You can find a more detailed description of the project that uses this small power supply on my blog.

If you'd like to build this project, make sure to also order the following boards:

• Logic board
• Capacitive touch ring