I awoke to news that my garage door was found open one morning. Nothing was missing, but I decided to build a door state indicator so I can know the state of the door at a glance (as they are on the other side of the building). I installed limit switches (sensors) on all the doors and built an indicator panel that can be easily seen from any of the Eastern windows of the house.

Supplies

Tools Needed

Drill and bits
Screwdriver
4-40 thread tap
Wire cutter
Hacksaw
Volt Meter

Parts we used

Limit Switches - https://amzn.to/2Hn7h9W
Indicator LEDs - https://amzn.to/2Hn7h9W
Power supply - https://amzn.to/2Hn7h9W
Wire - https://amzn.to/2Hn7h9W
Screws - https://amzn.to/2jJQcOw
Aluminum Angle
Steel flat bar

Step 1: Mount Your Switches!

This system is meant for entry doors, but can be applied to almost anything.

We drilled and tapped holes for the 4-40 screws we used to mount the switches, but you can use a screw and a nut if that's easier. It's a simple piece of angle aluminum. The switch mounts on one side, the other side is screwed to the wall.

Using whatever is handy, make some sort of switch actuator. A block of wood. More of the aluminum. All it needs to do is hit the roller on the switch when the door is closed. The idea is that the instant the door opens, the switch will open. This way, only when the door is fully closed will it give you a green light.

Step 2: Wire the Switches!

The circuit is quite simple and can be applied to as many doors as you want. We have three so that's the example.

The negative wire goes directly to the cathode of all the LEDs. Normally, there will be a resistor between the cathode and the negative supply, but the ones we used have it built-in.

The positive wire goes to the common contact of all the switches. The normally closed contact goes to the red LEDs. The normally open contact goes to the green LEDs.

Mount your LEDs in a prominent place and enjoy the security of knowing the state of your doors at a glance.