NFC-powered digital business card

How about a business card that, instead of beaming contact info to your eyes, it beams it to your phone! I wondered one swell afternoon. And so, it had to be made:
Theory of operation: A NFC chip which encodes VCARD information to a receiving phone. The chosen chip does not have its own power supply: it harvests energy from whatever Near Field it is surrounded by. It then encodes “transmitted” information in modulation of the field.

Some additional things i wanted to investigate is how much energy is harvested from the field: can one run another chip like an atmega with the harvested energy?

I made the design in the free online software easyeda. Reading up on antenna coil design I figured it’s best to use an existing coil design ( RF mechanics are a bit magic ahaha ). The design implements an existing coil antenna, separated from the rest of circuit to improve signal and reduce noise. An NFC chip is placed in the middle. Pads for an atmega chip located above it, to be powered by the nfc’s energy harvesting and some pcb big pcb pads connected to its adc/capacitive sensor pins to act as buttons. The logic part of the circuit has as much copper pour around and under it as possible to prevent noise.

One quick Pcbway order and short soldering session later it was time to test. Chip worked perfectly! There was more than enough energy harvested to power at least an led which should be enough for atmega chips in low power mode.

Using NFC Tools to program the chip, i found the vcard digital business card sendingworks perfectly! On android that is. Alas, turns out ios does NOT support vcard ( argh ) . At least ios still displays a transmitted website link

All in all it was a fun little project were I learned a lot about the nfc protocol, and about RF design.