A business card that beams contact information to straight your phone, instead of your eyes business card. That would be pretty swell eyes, it beams it to your phone! This thought entered my brain wondered one swell afternoon. So I had to make it!
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 by modulating that 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 that harvested energy
Now to make the design. It was made in the free online software easyeda.
To properly design an entenna coil I read up on antenna coil design. I quickly discovered RF Mechanics is magic. It is best to use an existing coil design. 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 it as possible to prevent noise.
One quick Pcbway order and short soldering session later it was time to test. The 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 modes.
Using NFC Tools to program the nfc chip, i found the vcard digital business card transmission works 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.
