Business cards are nominally convey contact information, and perhaps a bit about your business. If your card can do something useful – maybe as a compact PCB – that can make it really stand out when compared to other mere paper cards.
To celebrate his employer krumedia’s 25th business anniversary, Chris and company designed a set of 25 PCB business cards for each of the company’s two managing directors. Since they work in the industrial and municipal energy management sector, most of their customers “know what a circuit is,” and the cards were designed as non-contact voltage (NCV) testers/stud finders. They also feature NFC functionality for wireless info transfer – and visible text for when all else fails.
The first step in the build was to reverse engineer a commercial NCV tester/stud finder. This device uses an antenna to pick up on the signal emanating from live AC lines sans contact, and two op-amps process the input before feeding it to a microcontroller. The stud finder function is based on capacitive sensing.
This setup was adapted for business card use, leveraging a CH32V003 in a QFN package as the microcontroller and charlieplexed LEDs as the display. An ST25STA02KB chip was implemented as the NFC component.
To make things fit into the business card format, Chris used a .8mm PCB as the structural element, while placing the actual circuitry on a flex PCB. Both PCBs are stuck together with glue, and a the power supply – a CR2032 battery – is secured with a press-button and a tab from the flex PCB. It’s a clever solution, but was a bit of a “nightmare” since the button diameters varied slightly.
According to Chris, “Overall, the present was well received, even though it took longer than anticipated and we were only able to present it at the Christmas party.” Of course, any cool project is bound to take longer than you first anticipate. I’ve been through a much simpler version of this PCB business card journey, eventually settling on something with no components whatsoever!