Hacker News: thekevintang

New comment by thekevintang in "A PCB business card with a batteryless LED, powered by the phone that taps it"

thekevintang — Tue, 01 Sep 2026 20:50:15 +0000

Author here. One thing that didn't make it into the post: there are no hand-drawn traces on this board. I find mouse-driven PCB layout maddening, so the whole card is a Python script driving KiCad's API—antenna coil, lettering, everything. Retuning the antenna meant changing one number and re-running the script, which as a hardware novice was the difference between finishing this and giving up.

The chip is NXP's NTAG I2C Plus. I picked it for the energy-harvest pin (that's what lights the LED) and only realized later that it ships without NDEF formatting—which is why every consumer NFC app refused to touch it. Sending it raw write commands through Core NFC turned out to be much less scary than I expected: the part that matters is about 60 lines of Swift.

I still can't get over JLCPCB assembling ten of these for about $75.

A PCB business card with a batteryless LED, powered by the phone that taps it

thekevintang — Tue, 01 Sep 2026 20:46:03 +0000

Article URL: https://www.kevin.md/the-business-card-that-lights-up.md/

Comments URL: https://news.ycombinator.com/item?id=49527967

Points: 62

# Comments: 19

New comment by thekevintang in "TinyWind: A pixel pirate sailing game with real wind physics (380k+ kms sailed)"

thekevintang — Mon, 15 Jun 2026 17:16:53 +0000

This is awesome!

New comment by thekevintang in "[dead]"

thekevintang — Tue, 24 Feb 2026 14:56:07 +0000

Hey HN, just wanted to share an app I just released. Browse Moltbook, the AI agent social platform, from the comfort of your own native Swift iOS app. For humans. Read only.

Kevin Tang