I’ve put together a wooden box with a dot matrix screen which uses a Raspberry Pi and FlightRadar24 to let me know what aircraft are over my house. It has some big magnets on the back which let me mount it to my fridge. When there’s nothing overhead it shows the date, time and the temperature outside. It’s also quite pretty.
What, why?
Once the lockdown restrictions started to ease off my wife and I quickly realise the serene neighborhood we’d moved into was directly on the flight path for Glasgow airport. We’re far enough away that the windows don’t always shake but close enough to start noticing the difference in how each plane sounds. How cool would it be to say, “that sounds like a Engine Alliance GP7000, must be an Airbus A380”? Not very, but that didn’t put me off building something to tell me what aircraft are nearby.
Plan A was a split-flap display like at the airport, but that was either going to be more effort or more money that I was willing to put in. Instead I’ve pieced together something far sleeker.
Custom box
As soon as I seen the 32×64 Adafruit LED RBG Panels on Pimoroni I knew exactly what I wanted the final product to look like. As close to a featureless box made from a light wood with the matrix display flush with the front, just deep enough to fit the electronics. I wanted it to float weightlessly on my fridge with a single slightly fancy looking cable running into it. I took to illustrator, made up a plan and went searching for a local carpenter to help me build what was in my head. Thanks to LinkedIn I found Lee Turnbull who is an engineer and a fantastic joiner.
After sending him my plan he put together a design and with a little refinement Lee suggested going for interlocking laser cut birch. Inside the box there’s some big screws driven into the standoffs to give the screen’s magnets something to attach to. On the back of the box there are some screws with neodymium magnets built in which allow the screen to be mounted to my fridge. There’s then a bit of neoprene attached to the back of the box to prevent it from slipping once up on the fridge.
Once he was done the only thing standing between me and the box was the Hermes courier. After a week of lost-parcel-terror the finished product was delivered to much rejoicing and swearing about how crap Hermes are.
(Pro tip: if you’re too Scottish sounds for a poorly implemented voice-recognition system to direct you to a human, I recommend using the text-to-speech feature on your computer)
Electronics
Thankfully the tricky electronics required to run the screen are taken care of by another great product on Pimoroni, the Adafruit RGB Matrix Bonnet for the Raspberry Pi. This also cemented the decision that this project was going to be built around a Raspberry Pi. I went with a Pi Zero W to minimise how much space would be needed inside the box.
Power comes from a 5v supply brick normally used for powering LED light strips. That cable is nowhere near tasty enough for the project so the plug was been swapped out for a Lemo 0B push-pull connector and paired with it’s panel-mount partner. Any excuse I’ll use these, they are gorgeous – totally the wrong kind of connector for the job, but gorgeous.
I’ve added a little extra pizzazz to the cable by jacketing it with some purple braiding and a little heat-shrink for strain relief.
A power toggle wasn’t in the original plan but I figured an extra LED and a switch that looks like a tiny antenna wasn’t to be passed up. The switch is a NKK SPDT with a little red LED at the end of it.
To keep everything tidy inside the box I used a small strip of Veroboard to pull together:
- Incoming power
- On/Off switch
- Raspberry Pi power input
- LED and current limiting resistor
To bring power from the panel connector to the Veroboard I used the left over length of cable from the power supply with the ferrite choke. Leaving the choke on helps to clean up the supply voltage. The remaining part of the cable with the barrel jack on it is used to hook up the Raspberry Pi to the Veroboard. So it doesn’t get fried the LED needs a little inline resistor to limit current, a back-of-an-envelop calculation and a rummage through my toolkit revealed a 330R would do t
