This is a variation on a couple of previous garage door status indicator projects posted by others here on Instructables. The project employs 3 bipolar LED’s to show the status of 3 separate garage doors, where green = door closed and red = door open. A magnetic reed switch pair is mounted at each door. Magnetic switches were chosen because they can be out of alignment by an inch or two yet still provide the correct position status. So mounting is much easier than with a micro-switch and long-term performance should be more reliable.
Step 1: Circuit Design and Parts List
The circuit design is pretty simple.
These particular reed switches have 3 screw contacts; normally open, normally closed, and a common terminal. This design allows a bi-polar LED to toggle between red and green. I do not like the idea of using a single state LED to indicate the door status and the LED off condition to indicate the opposite status. No light can also mean that the power is out or a wire is broken and your door is wide open.
The LED’s, switches, and a 10-pack of 100 ohm resistors cost under $20. I used an old cell phone charger transformer rated at 4.5 volts and 5W. Alternatively, you could use 3 AA, C, or D cell batteries to provide 4.5 volts. The resistor was soldered to the positive lead of the transformer output which then connects to the common terminal on each switch. If your project has fewer or more doors, no problem. Each switch/LED is wired in parallel and the LED’s use very low power. The resistor uses most of the juice. The transformer (mounted in the garage) was checked with a Kill-a-Watt which measured 2.5 watt power consumption. That works out to 1.8 kW-hr per month which costs about 20 cents.
Parts List - sourced from Parts Express - http://www.parts-express.com
qty -------- part description ------------------------- part number
1 ---- 4.5V DC out transformer (my spare parts bin) ----- n/a
120 ft ---- telephone wire, 4 conductor (my spare parts bin) ----- n/a
1 ----- 100 OHM 1W FLAMEPROOF RESISTOR ---- 003-100
3 ----- REED SWITCH AND MAGNET ASSEMBLY ---- 060-207
3 ----- BI-POLAR TRI-COLOR 5MM RED/GREEN LED ---- 070-055
Step 2: Magnetic Switch Mounting
The switches were mounted above the garage doors on the header joists, with the magnets mounted on the top of each door. The magnets had initially been mounted on the side of door, but the door lift cable sweeps that entire area and tore off the first magnet that was tested. The magnet is attached to two strips of plumbing strap that are screwed to the door. The strap is flexible enough to be bent into position but rigid enough to stay in place.
Old land-line telephone hookup wire (18 or 20 gauge) was run from the switches and into the house via an underground conduit that had been placed when the 3-car detached garage was constructed. You could substitute other types of wire, like Cat 5 ethernet cable.
Step 3: Status Indicator Mounting
The wires (2 x 4 conductor) were run into our doorbell chime plastic case and the LED’s were mounted in the bottom, directly above the air vents. This just happened to be the most convenient mounting location for the LED’s. The doorbell and its transformer are completely independent of this system. The chime is in a central location inside our house at the base of the stairs to the second floor. So we always see the door status indicators before heading up to the bedroom each night. This also makes a great night light for those late night trips to the kitchen.
Step 4: Thanks for Viewing
My wife and I enjoy the peace of mind knowing that the garage doors are all closed at night without having to step outdoors to check. This is worth much more than the time and money spent on this project. Good luck with your own project.