How to Use Smarthome Door Sensors Around Metal

Open/close sensors, like those included with the Samsung SmartThings kit, are great for automating certain actions whenever doors or windows are opened. But if you’re having trouble getting them to work well, it might be because the metal on the door or window is causing issues with the magnet system that’s used on the sensors. Here’s how you can get around that.

The workaround is quite simple, although it doesn’t look the prettiest and doesn’t quite blend in. But it at least works. The sensor basically needs to be at least a few inches away from the nearest piece of metal to prevent interference.

First, try to mount the sensor normally to see if it works first. Even if a door does include some metal, it still may work just fine. It’s mostly doors that are heavily made out of metal (like garage doors) where you’ll usually come across problems. If you do, though, this trick should help.

The image above shows what the final product looks like—a door sensor mounted to the top of my garage door that’s a few inches away from the nearest piece of magnetic metal. Setting this up is pretty simple, but requires a bit of creativity.

What You’ll Need

To do this, you’ll need a couple of tools and materials, including:

The aluminum flashing (shown above) will come in an L-shape when you buy it, but it’s pliable enough that you can bend it all into a flat piece using light taps with a hammer. It’s one of the reasons we’re using aluminum for this: it’s very soft and can bend easily to your will, allowing for the most customizability. It’s also non-magnetic, so it won’t interfere with the sensor.

Step One: Mount the Sensor

We’ll start by mounting the larger sensor portion off to the side by a few inches from the door (or above). In this guide, I’m doing this with my garage door, so it’s a bit different than a regular door, but the concept is the same. Plus, you’ll likely have to make some changes of your own to make it work for your specific situation anyway.

In any case, you can either mount it using the included screws or 3M adhesive strips. Screws allow for a more solid connection, while 3M strips are quicker and easier, but there’s a risk of the sensor falling off if the adhesive weakens over time.

Step Two: Fabricate An Extension Arm for the Magnet

Now comes the difficult part. The smaller magnet portion of the sensor needs to be mounted to the door, but also needs to be a few inches away from it. To make this happen, we need to make an extension arm that connects from the door to the magnet. This is where the aluminum flashing comes into play.

As mentioned above, flatten the aluminum into a strip using a hammer—it shouldn’t take a lot of effort, and you can even use your hands to do a lot of the bending.

Then, from one end, measure a few inches in and bend it to a right angle to create an “L” shape. You may not have to bend the aluminum at all depending on your door and where you mount the sensor, but I had to in my case. This small section is what will be mounted to the door.

After that, take your sheet metal snips and—at the other end—cut the aluminum strip down to the specific length that you need.

You’ll end up with something looking like this:

Step Three: Mount the Extension Arm to the Door

Before you can mount the extension arm, you’ll need to take your power drill and drill some small holes where the sheet metal screws will screw in. You’ll also need to drill the same holes into your door where you’ll mount the extension arm. These holes need to be just slightly smaller in diameter than the sheet metal screws.

Next, take your sheet metal screws and screw in the extension arm into the door using your power drill and a Phillips drive bit.

At this point, you can make some fine adjustments to the aluminum and bend it to make it fit well. Keep in mind that you’ll need enough room in between the extension arm and the sensor to attach the magnet.

Step Four: Attach the Magnet to the Extension Arm

Lastly, attach the magnet to the extension arm. Make sure you mount it to the arm in a place where the magnet rests right beside the sensor. Screws won’t really work here, so you’ll want to use the included 3M adhesive strip to mount the magnet.

As mentioned above, it doesn’t really look all that pretty, but it at least works, and it’s the best solution to have your open/close sensors work around metal doors and windows.

Craig Lloyd writes about smarthome for How-To Geek, and is an aspiring handyman who loves tinkering with anything and everything around the house. He's also a mediocre gamer, aviation geek, baseball fan, motorcyclist, and proud introvert.