How Do Garage Door Sensor Work?

For safety reasons, garage door sensors have been installed on all doors since 1993 to prevent accidents, which can lead to serious damage and injuries. So, the main function of these sensors is that if they notice something between them, doors will stop closing and reverse. Electric garage doors are practical in many ways, and a lot of people use them to open and close doors without any effort and without having to get out of their vehicle: so how does the sensors work? In this article, we’re going to explain basic principles of how these sensors work.

How Does a Garage Door Sensor Work? The garage door sensors work with two units that are placed on either side of the garage door. One sensor is sending infrared beam of light and other sensor is receiving that light. If one of that sensors is misaligned, the sensor will signal a problem and the garage doors will reverse.

Since these door sensors began to apply, the number of accidents has decreased significantly. The garage door sensors are powered by electricity that is transformed into infrared light and they are set to 6 inches off of the ground. The invisible infrared trip wire is created among those 2 sensors and they can detect any object at that height such as a small child, five, or a car tire.

We also talked about How Much Electricity (kWh) Does a Garage Door Opener use, so if you are interested, take a look. You’ll be surprised!

Are Garage Doors Required to Have Sensors?

The garage door sensors are very useful safety tools, but are they required by the law? Can you reduce the cost by choosing a garage door without sensors? The Garage door sensors are required by the law and you can’t decline it anywhere in the United States. Since 1993, U.S. Federal Law has determined that all garage doors must include sensors for safety reasons. Each garage door must have at least one safety device installed on the door.

How Far Off the Ground Should Garage Door Sensors Be?

As a general rule, the height at which garage door sensors are placed is six inches above the floor. The reason they are placed at that height is because they will trigger properly, leaving as little space as possible for someone to crawl under and thus avoid accidents to trap children, people or animals.

If the sensors are set too high up, it can happen that a small animal or child won’t break the laser beam of the sensor, and the security system will not trigger. Therefore, adjusting the garage door sensors to the correct height helps you to prevent injuries.

How to Check If Garage Door Sensors Are Working

Garage door sensors are primarily designed to avoid serious injuries and save lives automatically when the doors are closing. All electronic equipment, including sensors, have their own lifespan and can break down, which can be quite dangerous if not noticed in time. If you want to check if your garage door sensors are working, you need to do the following steps:

Step #1: Measure the Height Of The Sensors

The first thing you need to do is to measure the height of the sensors on your garage door. After that, get a few cardboard boxes that exceed the height of the sensors.

Step #2: Set the Box Between the Sensors

Second step is to place the box in front of the garage door so that the infrared beam of light from sensors hit the box. Next, press the button for closing the garage door and see if the sensors will trigger and detect the box. If the doors stops closing and return to the starting position (reverse), the sensors work, but if the garage doors closes and crush the box, then it is necessary to check the sensor.

Step #3: Check the Sensors LEDs

Next thing you need to check is the sensors infrared light. Each unit of sensor has LED infrared light. See if the one of the LEDs on the sensor is blinking. If so, the sensors need to be realigned. This means that the infrared beam of the sensor does not overlap with the other sensor and needs to be adjusted, and you will do this by tightening them with the screw that is holding the sensor. When you do this the LED sensors will stop blinking.

Step #4: Make Another Test

After testing, remove the crushed box, and replace it with new ones. Place new box in front of the open garage doors between that two sensors so the infrared beam cuts the box. Now click the button to close the door and see if the garage door will stop and return to its open position. If the garage door continues to close, then there is probably a problem with dirty lenses on the sensors.

Step #5: Clean the Lenses On the Sensors

Finally, after you clean the lenses on both of the sensors you  can run another test. The most common problems are dirt and spider webs which can cause interference, thus disabling the sensors to work. Also make sure the sensor wires are not damaged.

Repeat the testing in the same way you have done before. If the problem persists, then you will most likely need to replace and buy new sensors because these are damaged. During the bad weather, these sensors can be damaged by rain.

Related Article: Can Garage Door Opener Work Without Sensors?

Do All Garage Door Sensors Work The Same Way?

All garage door sensors are designed to work the same way, because they have the same purpose. Although, these sensors work the same way, there are several different brands on the market. Those different brands differ only in price and quality.

Some of the popular door sensor brands on the market are LiftMaster, Chamberlain, Craftsman etc. But despite everything, these sensors will provide you with the same level of safety. In the end it’s up to you to to choose whether you will invest more money or opt for a cheaper solution.

How Much Does Garage Door Sensor Cost?

According to the average price, garage door sensors can be purchased anywhere between $ 150 – $ 200. That’s how much a new sensor replacement costs. $200 is the maximum limit you should pay for a new sensor.

This is because of a complete sensor installation costs around $50. Regarding garage door cable replacement with which the sensors are connected, the price is around $80.

Can Garage Door Sensors Be Repaired?

Yes, the sensors on the garage door can be repaired without calling the technician. Some of the most common causes of sensor failures are dust, poorly placed sensors, etc. If you decide to repair the sensors on your garage door by your own, first disconnect the power to the sensors. If the problem is related to wiring, call a technician because you will not know how to properly address this problem and it can be dangerous. In some cases, the sensors fail by human error. Some of these problems are: dirt on the sensors that are receiving or sending the beam of light, poorly installed sensors, etc.

Garage Door Sensors For Thieves

A conventional opening sensor detector operates using two components connected via a slight magnetic field. As soon as the garage door is opened by an intruder, the two elements are separated, which breaks the magnetic field and triggers the alarm system.

To secure a metal door, the same opening detection principle is used but with slightly different equipment. This time, the garage alarm uses a metal shoe installed on the floor or on the wall along the plane in which the door is located.

A wireless transmitter connected to the shoe completes the device to send the trigger signal to the alarm center. This transmitter is offset a few centimeters to avoid interference with the metal of the door. In some cases, the garage alarm sensor can also use a physical contactor (press a button, for example).


In this article, we have described the detailed process of how a garage door sensor works and its structure. As you have seen above, the integrated security systems in the garage doors automatically stop your door if an obstacle is detected.

This avoids the most serious accidents, especially for children. But this only works after the contact has taken place. Sensors are the ones that, when they see something, send a feedback signal and stop the door from closing. I hope this article helped you, and if you have any additional questions, please comment.

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