Prevent overhead garage door from closing when car liftgate is open or car is sticking out of garage but above safety sensors

I found 1m (3ft) long 6 beam IR barriers made by a Chinese company that I purchased with two overhead garage door related projects in mind. I am installing one set vertically just above the safety sensors to prevent the door from closing if anything blocks the beams. The mandatory safety sensors aren’t effective enough as one could still be standing right under the garage door with one foot on each side of the sensor and the door will still close, or the car could be just out enough to be in the path of the door but not blocking the sensors. The IR barriers, mounted parallel to the guides/rails (name?) would detect both a standing person or car sticking out but not blocking the bottom sensors. The second set will be mounted diagonally between the vertical and horizontal rails in the area where an open liftgate would be so as to detect it and prevent the garage door from closing.

The barriers have a relay that can be set to either NO or NC via a jumper (it just connects one or the other pin of the relay so with a bit of hacking both are actually available just not via the terminal block). The idea is to have the barrier relay open the sensor circuit as that would stop the garage door opener from closing the door. This will be much faster and more reliable than trying to go through ST. When the barrier detects something blocking either one of the barrier sets, the corresponding relay will open (they will be wired in series) breaking the sensor circuit thus stopping the garage door from closing. I will also add a simple switch to override these barriers (in case of unforeseen issues such as low sun shining on the barriers) by forcing the circuit to closed regardless of the relays in the barriers. My garage door opener has an integrated battery so it an operate during a blackout while the barriers will not. Without power the relays in the barriers will be at rest therefore, if set on NC setting, the garage opener will just work normally without the extra security.

Where does ST come in?

I will either use an Aeon Dry Contact sensor to detect the barrier status or a MIMOlite to detect and add some control (such as disabling the barrier remotely if needed). I have a camera covering the entire garage so opening/closing and disabling the extra security can be done safely even remotely. I would not want my barriers stopping me from operating my garage door opener while I am away… This setup can also be used for intrusion detection when your garage door is open.

As the projects progresses I will add pictures and info in this thread.

1 Like

I personally would NOT use ST to communicate safety issues between a garage door control and any added safety relays you install. I would run those directly to the garage door controller. This seems to be exactly what you are doing but I wanted to be clear on this for other readers. ST does go down occasionally and a garage door opener, even with safety settings it has, can still do damage to a vehicle (sorry truck bumper) :wink:

You could use a MimoLite in between as long as you set it to direct relay control. This would then notify ST and have ST push a notification to you but still have direct com with the door opener. A great idea!

For garage intrusion detection, I have a motion sensor installed above the door facing back towards the house. Someone walking in with ill-intent might know to look for those sensors, but would not be able to look above for a backward looking sensor without tripping my forward one.

1 Like

@clsanchez77 - Thank you for ensuring that aspect is clear. I should have stressed this more in my original post.

The ST portion of the project is just to detect status and possibly to remotely override the barriers in case they are malfunctioning and preventing the closure of the garage door when we are away (say we forgot them open or they did not close when we left and pressed the button on the remote).

The barriers have a relay that will be normally closed and will be wired in series with one of the garage door opener sensors. When the barriers will detect the IR beams being blocked, the relay will open the circuit thus disconnecting the sensor. Doing so will stop the garage door opener from being able to close the door as it will detect an issue with its safety sensor (issue = sensor not working/not connected).

Based on my research, there is no way to add more sensors in parallel to the existing one as power and fault information both run on the same two wires. If I recall correctly there is a square wave that changes characteristics when a fault is detected - in other words it is not an open/closed contact.

I barriers are 1m /3ft long and are installed about 30cm / 1ft from the ground so it would not me possible for anyone to enter the garage as the standard sensors cover the bottom bit not covered by the barriers, and then you have the 1m / 3ft long barriers.

The MIMOlite would be used to remotely short the two barrier relay contacts so as to mimic a no fault situation. By shorting the two relays (dry contacts) you are closing the safety sensor’s circuit thus allowing the garage door opener to operate normally (if the bottom sensors do not detect obstruction, it will be possible to close the garage door)

1 Like

Just add more beam break sensors in series.

Not everything has to be “smart” to be a smart solution.


My two sets of infrared barriers will be connected in series. If either one detects an obstacle then the circuit will be broken as one (or both) relays will open.

Putting the standard garage door sensors in series, or parallel, doesn’t work (referring to modern Chamberlain garage door opener) based on what I read on specialized forums as the sensors communicate status with a pulse train or something along those lines. It is not a simple presence or not of some voltage.

“smart, safe, sensible” solution - SSSS :grin:

1 Like

Well researched - kudos for effort.

I do not believe the sensors will work in series as they are powered units. In the sense, I can see where parallel is an issue with additive power draws.

I believe this video goes into details of how the sensors communicate with the garage door opener and why adding additional sensors in parallel or series will not work.

Wow… I’m surprised it’s so complex. Oh well.

Why not use the new sensors to just cut the power to the door closer?
You can just use a relay to cut mains power so the door cannot close
That way you are not relying on Smartthings to do any control (although you could integrate for alerting)

Once again, I am NOT relying on ST for any control due to latency and impossibility to get 100% reliability. ST is just monitoring and informing. That was the whole point of a few posts above :slight_smile:

Cutting power to the opener will stop it from reverting direction (safety feature) in case the barriers detected an obstruction after the door was put in motion. Also my garage opener has an integrated battery backup so just cutting power to it will not do anything unless I do so inside the opener on the DC side. I would also have to deal with an external switching device (mechanical relay or even better an SSR) as the relays and circuits in the barrier are not meant to handle mains voltage or even the necessary current.

Part 1 of the project is nearly finished and working perfectly as intended. The 6 beam barriers I installed vertically will stop the garage door from closing by breaking the safety sensor circuit thus causing the garage door opener to blink its lights on/off to indicate there is an issue with the sensors and the door does not move or goes back up if it was. This is the same thing that happens if the standard security sensor is tripped. A very short delay after the 6 IR beams are restored, the garage door opener is ready again to close the door.

Having access to the attic above the garage, I was able to run Cat5e from one side to the other of the garage door. The cat5e cable is used to connect together the barriers on both side of the door. The side shown in the picture above is the one that has a relay in it. The other side (shown below) just requires 3 wires for power and a return signal to improve detection. In the picture below the bottom of the barrier bar is not secured to the rail and assembly is not completed so it looks messy and not quite straight.

The “control box”:

Behind this wall mounted 2 gang metal box is a one gang opening in the wall where the standard garage opener sensor wires are. The box screws nicely into the low voltage bracket’s holes so it will be very easy to restore the original condition as I did not make any modifications to the wall. On the left of the box you can see the Aeon Dry Contact Sensor that will tell me via ST if the barrier beams have been tripped. It is not necessary for the system to work but I like to have complete visibility of what is going on in the house via ST plus I can use it as an intrusion detection system as well.

The little black cable under the Dry Contact sensor is power from the 12V power adapter above. This power supply powers the barrier bars but also a dual relay board inside the box (behind the blank plate). The relays were necessary to 1) ensure that if power was lost to the barriers, that the garage door opener’s security sensors would be functional (circuit would be closed by default) and to 2) provide a clean “dry” contact for the Aeon Dry Contact device.

The IR barrier bars I am using were designed for intrusion detection therefore no matter whether you set it to NO or NC, if power is lost, the circuit will always be open. This means that if the house loses power, or the power supply it unplugged, the sensor circuit would be open preventing me from shutting the garage door opener. Given my garage door opener has a battery backup, this is undesirable. In order to ensure a working sensor circuit, I used a dual relay board that will close the sensor circuit if it loses power. Doing so defeats the barrier bars intentional design of causing an alarm to sound if someone cut power to the barriers but it doesn’t matter to me as that is NOT the main purpose of these bars, plus I am guessing that by the time an intruder even realizes what they are, the IR beams would have likely already been tripped (I doubt what I am doing is very common in an average home). I also wanted an easy way to disable the IR barrier in case of issues. I’ve had cases where bright sunlight in the morning prevented me from closing my garage door as it was hitting one of the standard sensors and I have no idea what will happen when the same will happen now that I have these IR barriers installed. Given I am always in a rush in the morning, if this issue were to happen, or any other for that matter, all I will need to do is unplug the power to restore normal functionality.

My choice of connectors was for convenience. I am sure there are better options. Ethernet connectors were an obvious choice given I used Cat5e for the wiring between barriers. The spring loaded speaker connector works well to connect the security sensors and if the wire ever gets ripped out (ie storing stuff in that corner), it is easy to restore connection with no special tools. For the wiring between the wall and the barrier I used a molded Cat5e cable cutting off one end. I might have to revise connections if they oxidize causing issues but this way anyone can make quick repairs as there are no exotic connectors used. I could also just use some of the anti-oxidizing compound found at electrical supply stores.

Part 2 will be installing another set of 2 barriers where I drew the red line in the picture below, one on each side. This will detect if the lift gate is open and stop the door from closing and damaging the car’s lift gate. We’ve had the new car for a couple months and I’ve done it twice already with a 3rd close call. Having the ability to close the garage door remotely increases the odds of this happening as you may not remember having left the lift gate open while unloading the car. I will likely use webCore to add some intelligence where the system can tell me there is an obstruction when I try to close the garage door.

Adding the second set of barriers will not require much wiring. Power can be the same for the vertical barriers and I will only need one additional wire (I have plenty of unused wires in the Cat5e cable) between the barriers (return signal as they call it). The relays will be wired in series so that any one of the two will open the circuit. The aluminum beams shown in one of the images will be what is mounted between the rails and the barriers will be secured to the aluminum bars.

EDIT: Edited to improve my description as the prior one was written in a hurry (kids needed attention)… sorry! It was a torture for me to read it again at a later time.


I also had the same problem, as i wanted the garage door to stop if my SUV trunk is open. For this I have used the existing Liftmastergarage door sensor at the trunk open height and stop if it is open. Then it became another problem as if my car is just inside the garage, the bottom one was supposed to identify and stop garage door from coming down

For the final solution, I purchased the following Photo IR Sensor with a relay. It supports AC & DC. I set it up default ON , and made in series with the existing Liftmaster sensor. Now I have detection at two points