This evening I finished up a quick prototype RFID entry system for our garage door. It turned out to be quite simple, yet wholly satisfying in a very geeky way. I thought I might share a bit of the process and how it went together. It’s very crude at the moment, but I’ve got plenty of upgrades planned out for the future.

[caption id=”attachment_282” align=”alignleft” width=”150” caption=”RFID Garage Entry Prototype”][/caption]

I started out with a Parallax serial RFID scanner. It does a reasonable job of scanning the tags. I’d love to find something that had a bit more range to apply to some other ideas, but the Parallax unit works perfectly for this. My plan was to use an Arduino derivative for the brains of the operation since I’m somewhat familiar with the platform. I decided on the Solarbotics Ardweeny as a low cost base for the ‘production’ board. That’s definitely more chip than you need for something this basic, but like I said, I’ve got future expansion plans! The only other major component is a relay that I’m using to trigger the door activation.

[caption id=”attachment_285” align=”alignright” width=”150” caption=”Reader Acrylic Assembly”][/caption]

One consideration of the design was how to protect the board from the elements. I decided to laminate two sheets of acrylic on either side of the RFID scanner, with the inner pieces cut to allow room for the on-board chips and wire connections. The edges are filled with a silicon caulk to keep things water tight, and the front face was painted black. This somewhat unorthodox approach was purely for aesthetic reasons. The Parallax reader has a red/green LED on it that is programmed to respond to activation with an authorized RFID tag, and the acrylic allows the light to bleed around the edges in an interesting way that gives the unit a nice glow around the edges at night.

One additional benefit of the Parallax board is this code sample that takes care of reading the serial output from the RFID reader. Starting from there I added a little logic to grant access to only certain tags, and a bit of timing logic to keep multiple reads from triggering the door more than once.

From there it was just a matter of putting the pieces all together. The Parallax card wired into the Ardweeny per the comments in the code snippet. I assigned one digital out to trip the relay when a valid tag is read. The indoor pushbutton switch for the garage door is located conveniently nearby. I simply soldered two wires to either side of the momentary switch on the back of the PCB and ran them to the relay. When the tag is read the relay is tripped for 600 milliseconds, completing the circuit on the garage door switch and up (or down) it goes.