The World’s Smallest Four-Channel Voltmeter?

A voltmeter is an essential tool for working with electronics, but like any other device, it takes up room in your toolbox/bag/desk. I’d argue that the standard Game Boy-esque voltmeter form factor is a reasonable tradeoff, especially since they typically come as part of a multi-function implement (i.e. multimeter). Alun Morris, however, decided to make what be the world’s smallest four-channel voltmeter. It’s capable of displaying four voltages simultaneously, with logic levels, in a size that can easily be held between your fingers.

The voltmeter employs an ATtiny1614 MCU for processing, taking inputs from a voltage divider setup that allows it to read 0-27V, and survive ±100V if things go out of range. For values of under 1V, it has an impressive 1mV resolution, and the system has a 0.1% accuracy that can be improved via calibration.

To achieve its tiny size of 18x21x11mm (well under a cubic inch), Morris used a perfboard with 1.27mm pin spacing for connections (as opposed to the more common 2.54mm), along surface-mount components and impressively intricate connection wiring. The largest component used is the .42 inch, 74x40 pixel OLED display, which shows the four voltages and logic levels simultaneously in a portrait orientation.

You can see a demo of the build below, and code/schematics/more info is available on Morris' GitHub page. While amazingly small, the improvements section notes that a bigger display might be nice. Perhaps the next version will be easier to see, even if it takes up a bit more room!