This Business Card Doubles as a Handy Battery Tester, Thanks to a WCH CH32V003 Microcontroller
Available under a Creative Commons license, this electronic business card is a step up from just printing a calendar on the back.
Mononymous self-described "electronics and rapid prototyping enthusiast" Greg has built an electronic business card that serves a second, practical purpose: a battery tester for those CR2032, AA, and AAA batteries you've got sliding around the bottom of your drawer.
"I've wanted to make a PCB business card that's likely to keep getting used, rather than just landing at the bottom of a recruiter's drawer," Greg explains. "A battery tester is something most even non-technical people might actually use, and if you also hand the person a battery to play around with, the 47 flashy LEDs will magically come to life and demonstrate that… well, I can make electronics and demonstrably they sometimes even work."
The card works as a business card in exactly the way you'd expect from an electronics enthusiast: the PCB includes a silkscreen layer that holds the owner's name and contact information, complete with QR Code for quick scanning. This, however, is positioned around a pair of cutouts in the board — sized so that you can slot a AA or AAA battery in place.
Once connected to power, the card's WCH Electronics CH32V003 microcontroller — a 32-bit RISC-V chip popular for its extremely low cost — fires into life and measures the voltage available from the battery, reading out the result on a surface-mount LED numerical display to the upper-right as well as a quick-read LED bar graph to the side. There's another area for testing a CR2032 battery, and an LED tester for good measure.
Greg has published design files and source code for the project to GitLab under the Creative Commons Attribution 4.0 International license; more information is available on Hackaday.io.