Leave your keys at home and unlock the door with your finger.
Chances are that, if you’re heading out without your car, you don’t always need to carry your keys everywhere you go. As a result, it’s likely that at some point, you’ve locked yourself out of the house or apartment. Instead of having to wait for someone to bring a spare or your roommate to come back, wouldn’t it be much easier and more convenient to access your door with just the touch of a finger? That’s the idea behind Maker albedozero’s latest project: a garage fingerprint lock.
Inspired by a previous device from fellow Instructables user nodcah, this DIY system is built around a SparkFun GT-511C1R fingerprint scanner (FPS) and is comprised of two parts: an outside control panel, which houses the scanner along with a Nokia LCD screen and three buttons inside a weatherproof acrylic enclosure, and a small box within the garage that authenticates the fingerprint.
An ATmega328P MCU serves the brains of the exterior control panel, while an ATtiny85 drives the interior unit. Both MCUs communicate with one another over a serial connection. The tinyAVR biases a transmitter to close the connection for the door switch whenever it receives a specific code phrase. As albedozero points out, this way a mildly clever burglar can’t break into the house by simply ripping off the control panel and crossing a couple wires.
“Though the datasheet claims this FPS can handle up to 6V, I’m skeptical since the better model requires 3.3V, and since the MCUs are happy with 3.3V and the LCD requires it, we’ll just power the whole thing that way,” the Maker explains. “I cut the microUSB connector off of an extra phone charger to power everything, since they’re cheap and easy to come by if you stay away from the Apple Store. You could run the whole thing with batteries, but the FPS must drain a lot of power because when I tried it with 3 AAAs, it only worked for about a day.”
How it works is pretty straightforward: Pushing any of the buttons will illuminate the screen and scanner, prompting its user to place their finger on the touchpad. If recognized, the garage will open and a menu will appear enabling user to do everything from close the door, to delete fingerprints from the scanner’s memory and change the brightness of the display. For the most part, the system will time out after about eight seconds, turning off the screen and scanner, and requiring authorization in order to return to the home menu.