Simple 125kHz RFID reader proof of concept test

The idea is to come up with a reliable but simple and cheap RFID reader that doesn't rely on custom chips or modules. Ideally, without using a tuned circuit in the transmitter so that the frequency of the reader can adapt to the exact tuning of the RFID tag. I'll be doing further development. For this test, I just wound a coil with about 20 turns or so roughly the size of the RFID tag. No calculations done. It is driven via a 150 ohm resistor from a signal generator tuned to 125kHz for this video. The scope is connected directly across the coil. The concept used is that when a tuned circuit is placed in the field of an untuned coil being driven at the resonant frequency of the tuned circuit, the impedance of the untuned coil takes on the characteristics of a circuit at resonance. The peak AC voltage rises. Tests done off-camera indicated that the actual peak of that particular RFID tag resonant frequency is closer to 128kHz, but testing indicated that the backscatter radiation from the tag still clearly works at 125kHz. This was from a Meetup for OlyMEGA, a maker club in Lacey/Olympia, WA. The meetup was called Let's design an RFID reader without specialized ICs. http://www.olymega.org http://www.meetup.com/OlyMEGA