ATX Power Supply with Ammeter

For this project, I took a computer ATX power supply and wired an Arduino Nano internally up to an LCD screen and three current sensors to get a digital ammeter built in, without having to disconnect the circuit.

The Story Behind the Project

I made this when I was just starting to get in to programming LED strips and was trying to figure out how much current they draw. I discovered that once you get over a few amps, my multimeter connections were poor enough that the added resistance affected the circuit, making the readings inaccurate. Furthermore, you'd have to disconnect the circuit to insert the multimeter, which was often difficult, and required rebooting any processors that were involved. This project eliminated the need to disconnect the circuit, and ensured good connections. It's also way more convenient than a multimeter.

Features

• The LCD shows realtime current draw for the 3.3V, 5V and 12V rails simultaneously

• A hole in the front panel allows for USB connection to the microcontroller for the ability to reprogram it while it's running. A diode ensures that power doesn't back feed either way

• A hole in the back of the supply allows access to a potentiometer to adjust the display contrast for different lighting or adjustments for USB vs. wall power