How to Install a "garage Door Open" Indicator





Introduction: How to Install a "garage Door Open" Indicator

Ever left your garage door open overnight? In addition to being a terrible energy waster, all the tools, bikes, and other stuff are available to thieves - who might even enter your home via the door from your garage to your living quarters.

Install a simple indicator which will alert you if you've left the garage door open. Total cost is less than $30-$40, and you can determine exactly where the indicator will be located.

What you'll need:

-A 24 volt doorbell transformer
-1 push button "normally open/momentarily closed" switch
-1 red LED - 2.8 volts
-1 4.7k-Ohm resistor (specific part numbers for the electrical components are provided in Step 2)
-2 strand bell wire
-Electrical tape and/or heat shrink tubing

-Wire strippers
-Soldering iron + solder
-Electric drill
-Misc. hand tools - wrenches, etc. - depending upon the specifics of your installation

Let's get started...

Step 1: Identify a Switch Location

Your first step will be to determine where you can put a switch to close the indicator LED circuit.

When I looked at my garage door, I noticed that a piece of galvanized trim on the top of the door stopped right next to the angle iron used to hang the door tracks when the door was in the fully opened position.

I bought a simple corner or "L" bracket and mounted it from the bolt that connected the wheel track of the door to the vertical angle iron bracket. A simple Radio Shack "normally open/momentary close" push button then mounted on the other side of the corner bracket, with the switch of course facing the top of the door.

By bending the bracket slightly, I was able to ensure that the switch was fully depressed every time the door was fully opened.

This arrangement might work for you, or you might have to improvise a bit. You of course want to mount the switch in a manner that it's in the "closed" position when the door is open.

NOTE: in the image below, I stopped the door's movement before it reached the fully open position so you could see the orientation of the switch in relation to the top of the door. When the door is fully open, the red push button is fully depressed, and the circuit is closed. (See 2nd picture below.)

Step 2: Wiring Diagram

Before we go any further, a simple wiring diagram.

The system uses a 24 volt doorbell transformer as the power source; a 4.7k-Ohm resistor knocks the voltage down to that required by the LED (~2.8 volts.)

All of the electrical components are available at Radio Shack and will cost approximately $6.

In addition, you'll need some 2 strand bell wire; how much depends upon where you plan to put the LED. More on this later.

All of the Rat Shack part numbers are indicated in the diagram.

Let's take a look at how I mounted the doorbell transformer in the next step...

Step 3: Wiring the Transformer

I used a variable voltage (8-16-24 volt) doorbell transformer made by Heath/Zenith. It cost about $15 at my local home center. You need a transformer that produces 24 volts.

I direct wired the transformer to a grounded, 3 prong plug and mounted it directly above a power strip near my workbench. The 4.7k-Ohm resistor was soldered in place and then secured with a piece of heat shrink tubing I had on hand; it's directly beneath the transformer in this picture.

If you wish, you could cover the wiring with plastic channel for a neater appearance; I simply chose to use insulated staples.

One other thing I did later on was to plug the power strip into a lamp timer, and set the timer so the strip is on only between 8pm and midnight. There's no reason to power the transformer 24/7, as the only critical time is at night when we're going to bed and (presumably) have forgotten to close the garage door. Which leads us to the final step...

Step 4: Install the Red LED Indicator

After thinking about this for a bit, I figured that the absolute best location for the "door open" indicator was in the master bedroom.

It could have gone in the kitchen, or mud room (whose door connects to the garage) but my logic was "if I could remember to look at an indicator in one of those rooms, I could just as easily remember to open the mud room door and check the garage door."

To be absolutely foolproof, I thought it had to be in the master bedroom. Looking around the room, I thought of getting at the ceiling light fixture via the attic, and perhaps placing the LED inside the light's frosted globe.

In the end, I decided to drill a small hole in the decorative trim on the light, oriented so it faces the head of our bed. That way, if the LED was illuminated, you couldn't help but notice it when you went to bed.

I was able to route the wire from the garage all the way through the attic to the location of the master's ceiling light. (NOTE: this was the most time consuming step in this project.) Working from the bedroom, I drilled a small hole next to the light's electrical box, within the diameter of the light itself. I then fished the wire through from the attic, and made the connections to the LED. (As with the resistor, the wires were soldered to the LED's leads, and everything secured with heat shrink tubing. You could use electrical tape for this; just make certain everything is sealed really well.)

And that's it. As mentioned earlier, I put the system on a lamp timer so it's operational only in the evening.

It works perfectly, and we're now assured that if we forget to close the garage door before retiring, the LED will bring us back to our senses.

Total cost of this project was around $40, and that included 120 feet of bell wire. YMMV; bell wire costs about $ .20 per foot.

If you've read this far and enjoyed this project, please consider visiting my blog - Practical Hacks - at



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Please be positive and constructive.




Is the white bell wire connected to the transformer? So, it seems like I
need to run the bell wires from the push button switch, with the white
going directly to the LED and red heading INTO the transformer and then
another red segment heading OUT OF the transformer, with the resistor
soldered in-line, and going to the other connector on the LED. Is this
correct? Additionally, if I were to modify this design for a 2-door application, I would need a separate resistor for the 2nd door correct? Or not?

The mission objective and notification LED is brilliant! As I understand it the way the switch is mounted: it senses that door is either fully-open or not fully-open. I would be interested in photos of sensors that confirm that the door is fully-closed or not fully-closed. The distinction is that in the photographed configuration, there is the possibility that the door is partially open, which would not trip the switch (LED notification). Again, this would be perfect reminder for renters that leave the door open.

I need something like this (or this exactly, in fact) because I have backed into my garage door too often, in too big a hurry to back out. This last time I backed out so quickly that we had to replace the door. I am going to install this to fully indicate that the door has opened, so it is clear for me to back out (No comments about women drivers, please!).

I have a commercial position indicator, but that won't quite work. The sensor detects whether it is vertical (door supposedly closed) or horizontal (mostly open). It does not indicate whether it is 100% fully open or closed.

So I will install this and put the LED (green for my installation) in my line of sight right there in the garage. Maybe I'll even get creative and make a sign that lights up that says "OK" or something.

Never backed into my garage door like this. Just wait for the door to open, then back out, not hard to do. Really, wth? Backing into your garage door is a normal occurrence? lol

I have three dogs that get rather chaotic when it's time to go for a "R-I-D-E." And one dog needs help getting in the car. Usually I open the door when we go into the garage, but if they are super chaotic for some reason, it has happened a couple of times that I think I opened it, but didn't. Our biggest is a Great Pyrenees, and if he gets in the way of the rear view mirror, I can't see a thing out the back.

Sh*t happens, what can I say?

I would think a better way to do this is to use a normally closed switch and mount it so it is pressed when the door is in a fully closed position. That way if the garage door is partially open the switch would be pressed.

Thanks Journeymanjoe for pointing out code violations. You are right the average DIY homeowner might not know these things. (Unless that person is also a Electrician) None of us would like a house fire...that would be way more costly then hiring a qualified repair person. I did find a helpful site if you all want to fix some other things...some of our rollers got unscrewed and fell the whole attachment came off.

Step #3 is a National Electrical Code violation and a hazard to anyone that comes near it! You can't have exposed energized parts over 50V (should be installed mounted to a box with the 120V wires inside the box), that is why they make these transformers (primary side is 120V and the secondary is 24V). It is a violation to use single conductors with this plug (the plug is made for use with a cable).

Step #4 is a National Electrical Code violation also, you can't modify a listed luminaire (drilling the hole in it); you can't mix the low voltage with the 120V power in the luminaire.

This is why homeowners shouldn't be doing electrical work, too often we hear about residential fires blamed on bad electrical wiring (would be nice to know how many were wired by the homeowner)! Please hire a professional, licensed electrician to do any wiring. The money you save by doing it yourself is not worth the risk to your life and property.

I have built a very similar setup for the same reason. I've used the doorbell itself as a "base station"; the LED is mounted inside the doorbell housing which is located in the main living area in a prominent position. The doorbell runs on four "D" cells, and I siphon off 3V from two of the batteries to power the indicator.
I notice you say "You need a transformer that produces 24 volts." Is this to overcome the resistance in the wire over the long distance to the garage door? I found the 3V from the batteries works fine on mine, and the wire goes for about 20m (60ft). I think there is a loss over that distance but the LED draws so little current that it doesn't matter.
Great instructable, kjc2010. We're obviously thinking along the same lines!

You state that there is no reason to power the transformer 24/7 and I agree.

Couldn't you wire this thing to power the transformer only when the door is open? The simplest way might require passing 120v thru your switch.