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  • cool project, especially as a bachelor student of EE!
    by danshagen
  • Really great project, thanks for sharing and what a well done write-up! Also kudos for including the PCB, BOM, and code on GH with a permissive license.
    by chews
  • What an incredibly neat hack, congratulations. In the 80's Motorola had a challenge-response system to open doors with badges that contained a good bit of circuitry that reminds me of what you've built here. Super impressive. I never realized NFC put out so much energy that you could light a bunch of LEDs with it and power a micro controller this large.
    by jacquesm
  • > I should explain how NFC works: Your phone emits a small magnetic field several times a second. An NFC card picks up on that field, making your phone act like a tiny wireless charger. The card never actually transmits a message back to your phone. Instead, it changes how much energy it absorbs from the field, and your phone detects those power dips and converts them to binary data. Most NFC tags use this harvested energy only to run their internal circuitry, but some NFC chips are able to take excess DC voltage and route it out to external hardware.

    Can somebody explain how this actually works (Physics + Technology) with pointers to further resources? I have been meaning to look deeper into "Energy Harvesting Systems" and running a MCU using that but never really sat down to research it properly. Some links;

    University of Washington - WISP (Wireless Identification and Sensing Platform) - https://sensor.cs.washington.edu/research/wisp_1

    Perpetually Powered Energy Harvesting Systems Using the MSP430 MCU - https://www.ti.com/video/3870842958001

    by rramadass
  • I would be really interested to know the cost per card, both at the single card volume as well as the 30 the author ended up getting.
    by cowthulhu
  • For future PCB business card ideas: it would be dope if it can play audios.

    Gemini says you can power a piezo buzzer (causing a small bump on a PCB) w/ NFC (just enough power to drive it) to play the modem dialup handshake audio.

    by yegle
  • "The card never actually transmits a message back to your phone. Instead, it changes how much energy it absorbs from the field, and your phone detects those power dips and converts them to binary data. Most NFC tags use this harvested energy only to run their internal circuitry, but some NFC chips are able to take excess DC voltage and route it out to external hardware. This business card uses that last feature."

    I wonder if it can be applied to robo-couriers and drone drop-offs. One of those comes to your door, you get your stuff, and you pass something that is powered-up over its sensor and it drives off. It's the equivalent of signing-off on a delivery. The sensor obtains and stores information about you as well.

    Maybe I've got it wrong and the recipient needs the sensor and the driver has the powered device that only switches on when it is ready to do the drop off.

    With this card, what are the information transfer and storage scenarios? Would be great to see a table. Can the two parties both exchange and store information with minimal power? A card with a little battery and power-on button? Card can have some type of port? Can it be be used as a crypto wallet with a kill switch in the event of a robbery or home invasion?

    I think this is important in Hub-and-Spoke communities (previous comment) where population densities decrease but there'll still have to be a lot of exchange going on. Offline-based interactions are a good idea too - keep the airwaves clean.

    by adrianwaj
  • Look at that subtle off-white coloring, the tasteful thickness of it. Oh my God, it even has a schematic
    by badatnames

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