The project originated as a submission for a scholarship contest at the arts conservatory I attend. The department in charge of door access card readers offered a couple thousand dollars in scholarship money for students who re-purpose their old card readers into something else.

As soon as I got the email announcing the contest, I signed up with the intention of hacking the card reader into some kind of noise making device. From experience on the front end, I knew that there was some kind of buzzer or beeper that indicated whether the card swipe was valid, invalid, or caused an error. There also exists 3 LEDs- green, red, and yellow on the reader that correspond to valid, invalid, or error-causing swipes.

After getting a confirmation email that the supplies were waiting for me, The department in charge of door access card readers and cards gave me 10 card readers and a funny look when I asked for documentation.

I found some general installation documentation after a couple Google searches, but nothing in terms of schematics. Somewhat frustrated, I opened one of the card readers up and tried to understand how the circuit functioned. From reading the skeletal documentation, and from what I could discern, the card swipe data is converted by a surface mounted integrated circuit, sent to the controller for processing, and the response is sent back to the card reader to indicate whether the swipe was accepted or not. The buzzer beeps, one of the LEDs light, and if your swipe is valid, the magnetic lock on the door opens, allowing you access.

My original intention was to use all of the existing circuitry and modify the function. Considering that I was missing most of said circuitry without the controller, I decided to instead focus on adding a component that would circumvent the parts of the circuit I didn't understand and instead focus on the parts that were more easily accessible. To do this, I bought an Adafruit Trinket in the 5V flavor. I'm sure that there's a better way of controlling a buzzer and 3 LEDs than with a micro controller, but I have a small amount of experience with the Trinket, and I understand its capabilities well enough to make PWM and LEDs function. Further, the Trinket will allow me to neglect providing power to the entire card-reader apparatus, just the parts that are critical to the functions I intend to utilize. (I hesitate in trying to construct an apparatus that delivers the specified 6-26V DC at less that 100 mA.)

More to come as I assemble a prototype.