Computers come and go, but when they’ve reached the (supposed) end of their usable life, they still have a wide array of useful bits that can be repurposed for something else. One of the most popular hacking targets of old desktop PCs is the ATX power supply. These beefy units produce 3.3, 5, and 12V power, making them perfect for a variety of Arduino/Raspberry Pi/general hackery projects. It’s a good option if you don’t want to fork over the cash for a purpose-built supply.
On the other hand, purpose-built supplies are generally adjustable for voltage, and give an output reading for how many amps you’re using at any one time. To solve the second issue — and actually make some improvements — YouTuber “OneMarcFifty” has come up with his own Arduino-based bar graph current display.
The device measures current using a trio of ACS712 Hall effect sensor modules, showing these values numerically, as well as on a color-coded graph to the left. This graph progresses with time, so that you can see patterns, and the graph’s scale, speed, and resolution is adjustable via interface buttons. Processing power is provided by an Arduino Nano clone.
4mm connectors for the different flavors of power are embedded in the device's enclosure. This allows it to supply different voltages at the same time, another enhancement over many purchased units. Code and schematic info for the setup is available on GitHub, and you can discuss on Reddit if you have any questions.