Leaving your garage door open can be a risk, even if you're home. Thieves could grab something, and animals can wander in. This setup uses a repurposed remote-controlled car and controller to create a light-up alert system that lets you know when the door is open.
In this video from YouTuber kipkay, you'll get step-by-step instructions for building your own open door alert system. You'll need an old RC car and remote -- it doesn't have to be fancy -- a magnetic reed switch, a 9V battery and a coloured LED light.
Once you have it all connected as instructed, and you've placed everything accordingly, the receiver will light up the LED as long as the garage door is open. Now you'll always know when you've forgotten shut it so you can keep your valuables safe. If you want to shut it remotely, you can use an Arduino to build a smartphone-connected controller.
Is Your Garage Door Open? [YouTube]