David Hunt doesn’t get out a circular saw to hack a hole in his door when he gets a dog. No, David Hunt aims for something much bigger, a difficult and precise project that is, functionally, about the same as a doggie door but much more rewarding. And silly. Here he presents the bark-triggered door unlocker.
Here’s the list of materials, from Hunt himself:
A Raspberry Pi in the centre, a motor driver PCB to the left. I used this because it easily allows me to send 12 volts to the actuator in either polarity, for pushing or pulling the door bolt. The PCB on the right is the audio detection circuit from Maplin. And at the bottom is the 12V actuator. The small veroboard PCB is just a voltage breakout with GND, +5v and +3.5v, to make the wiring easier.
The Raspberry Pi, a tiny, super cheap computer, listens for the bark with the aid of a noise detector. Then the printed circuit board (PCB) tells the actuator to move a metal arm, which pulls back the tongue of the door’s lock. That whole setup only unlocks the door, though; opening the door is a much simpler affair, with a weighted pulley system (and no computers).
Given that the unlocker needs a decent amount of space between the door and the doorjamb to pry the lock backwards, this isn’t exactly a secure lock system. And, um, it responds to barks, even from a human. But if the dog gets locked in the shed? Now it can make its way out, no problem. It may not be as complex as this cat face detector, but it’s certainly more impressive than a doggie door.