Pi-Rex: The Raspberry Pi-Based Dog-Door That Unlocks With A Bark!

Woof woof, and that's it! Your dog is the new Alibaba as far as unlocking doors are concerned, the magical spell being just its usual bark. New pet owner and Raspberry-Pi enthusiast David Hunt wanted to let his dog attend its early morning piss-call without having to depend on anyone, and he found a creative DIY solution in a rigged door that automatically opened with just a bark- a creation he's named Pi-Rex. In order to simplify the whole procedure, Hunt chucked the expensive camera gadgetry for a more affordable noise-detector circuit, backed up by Raspberry Pi and motor driver PCB circuit. When the mini computer detects the bark, the circuit prompts the actuator and a simple pulley system to open the door to a bladder-discharging heaven.


Here's how David recounts the process-

I picked up the audio detection circuit in Maplin as a DIY kit for €9.99, the kind of ones where you get all the components and a PCB in a bag, and solder them all together. It took about 30 minutes, but worked perfectly, I could bark, and the LED’s would light as I barked. My family thought I was gone mad when they heard me making dog noises in my workshop.

Electronics engineers will now cringe at what I did next. I probed the audio sensor with a voltmeter, and saw that when the volume into the microphone was at a decent level I saw about 3-3.5 volts at one point, so I hooked that directly up to the GPIO on the Raspberry Pi, and it worked beautifully. Ideally, a proper buffer circuit would be used to give a proper logic signal to the GPIO, but I’m not always one for the perfect solution, as is obvious by the fact that I built this contraption at all!

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.

All the wiring is done with dupont connectors, 0.1″ (2.54mm) pitch, just like the Raspberry Pi GPIO header. I got a crimp tool off eBay, as well as a a few dozen blank connectors and a roll of female crimps. Make cabling up this kind of project very easy, where you don’t want to solder everything into place.

Also, the code to read in the GPIO from the audio circuit has been given away by Hunt in his <a href="https://www.davidhunt.ie/?p=3132" target="_blank" rel="nofollow noopener noreferrer">www.davidhunt.ie</a>, so if you want to give your own dog this much freedom, you know where to look. Now it's a great invention, considering that your dog won't have to bark pointlessly in the morning, but if that dog is THE only "security" you have at your place, I'd recommend you to think a dozen times before making it this door.

Watch the video below: