This is a credit card ring design based on the work of user b00t3r at https://www.instructables.com/NFC-Payment-Signet-Ring-With-Minimal-Inductive-Ant/

The tap-to-pay function of this ring works very well on some readers, and alright on other readers. I found the point-of-sale terminals at Target are very sensitive and work great as well as terminals at some gas stations, however, some readers at vending machines and some other retail terminals are a bit finicky and take a bit longer to read the chip (as shown in the attached video).

I ended up using 29.5 turns of .1mm wire on this ring. I finished off the Elegoo Transparent Resin with a coat of clear nail polish to give a clear finish and secure the chip in the ring. I secured the antenna wire with super glue. I did attempt to coat the antenna in nail polish as well, however, I believe the thick application of polish heated up during curing and melted the enamel on the wire, shorting it out. I settled on super glue to keep it in place.

As always, attached is a Fusion design file as well as a few different ring sizes. The .f3d file should make it easy to resize the ring quickly by simply modifying the diameter in the 2nd sketch.

https://youtube.com/shorts/LDT-w90gh-M?feature=share