RC522 RFID Card Reader

Wave a MIFARE card over a small PCB antenna and watch its unique ID land on the serial monitor.

Difficulty: Breadboard. Estimated build time: about 40 minutes. Estimated parts cost: about US$6.00. 8-part bill of materials with live supplier pricing. A short-range contactless card reader built around the NXP MFRC522, the same chip family that lives inside transit-card validators and office door panels.