A bench power supply is one of the first tools an electronics student wishes they had at home, yet most units are heavy, mains-tethered, and too big for a dorm desk. That gap is what Ben Makes Everything set out to close with a portable supply that fits in one hand and runs off a battery, so you can probe a circuit at your workbench or on the ride to class.
The device works like a USB power bank with a brain. Instead of a fixed 5V, it delivers adjustable voltage with live current monitoring, giving you the same control as a benchtop unit in a package the size of a deck of cards. A rechargeable pack means no wall outlet, and a micro-LED fuel gauge shows how much runtime is left before you need to top it up.
What's inside the enclosure
The output ranges from 0.8V to 22V, wide enough for a 3.3V sensor rail or a 12V motor test. Charging happens over USB-C Power Delivery, and energy comes from a 4500mAh 4S1P lithium-ion pack. The heart of the build is a Microchip ATtiny3216, an 8-bit microcontroller that reads a rotary encoder for user input and drives an HCMS-297x LED display for status readouts. Ben packed the power management, charging, regulation, and current-sensing ICs onto a single custom PCB, which is the only way to keep the whole thing this small.
Build it yourself
This is a solid intermediate project if you are comfortable with SMD soldering and reading a datasheet. You will need:
- A Microchip ATtiny3216 and a UPDI programmer to flash the firmware
- An HCMS-297x LED display and a rotary encoder for the front panel
- A 4S1P lithium-ion pack near 4500mAh plus a USB-C PD charging IC
- The custom PCB gerbers and firmware from Ben's GitHub repo
The enclosure pairs a 3D-printed body with a CNC-milled aluminum faceplate, and the faceplate prints fine too if you have no mill. Grab the full source files from the original build write-up on Hackster and start by ordering the PCB.
Originally published on blog.circuit.rocks.
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