Stupid Simple Arduino LF RFID Tag Spoofer

Step 5 The code

 The Arduino now needs to tune and detune the antenna.  When pin 9 is low then the antenna is tuned (sending out a "high" signal).  When the pin is high then it sends power to the base of the transistor.  This reduces the resistance between the two ends of the coil, which "detunes" the antenna.  We just need to do this in the right sequence to send data to the reader.  The code generates a tag ID that's 10 hex F's.  If that's what you get in your reader then you know it's working.