Here's what I've done. I'm not fancy, so the look may not appeal to everyone. My house is old and far from pristine.
This one is at the top of the door frame, because a window at the side will not allow enough depth for the sensor. I originally did this for my iSmart Alarm sensors, but at my back door I have less flexibility to add an additional sensor in this way, so one of my Xiaomi Aqara sensors is just surface mounted. This may change, but I'm not sure if iSmart Alarm is going to be around much longer, and I don't know what I'm going to replace it with yet, so that's basically my door of indecision at the moment.
Here's the magnet recessed in the top of the back door. This is unseen so no need to cover the hole.
At the front door, I have a small mortise for the iSmart Alarm sensor, and a very large mortise that was originally for an Insteon sensor. Now that it has a tiny Xiaomi sensor in it, the opening seems ridiculous, but it does the job just the same. I put a small block of wood at the back of the opening to keep the much smaller Xioami sensor as close the opening as possible in this oversized hole. If you get these positioned just right, you can get the sensors to trigger when the door just barely moves. So if the door isn't completely closed, the sensor will still show open, and that's great for a RM condition that prevents your door lock from operating unless the door is fully closed.
Here's how thin the plywood is. Don't remember where I got that really thin plywood from. I think it was a slide open cover from a wine gift box. Hobby shops will usually have really thin plywood available. Screws are counter sunk into the plywood so the door doesn't catch on them.
Here what one of the front mortises looks like. In experimenting, I found the sensor worked better in one orientation, versus the other for some reason. That's why it's marked that way.
I tape tabs of masking tape onto the sensors, just to make them easy to grab when I need to change their batteries.
Here's one of the two magnets that are embedded in the front door, and then the hole was covered with calking. The other (not shown in this photo) is for the iSmart Alarm contact sensor.
NOTE: I did experiment before cutting anything to make sure one of the magnet poles would actuate the sensor and which was the best, since it doesn't expose the side of the magnet to the sensor's reed switch as it does in an out of the box installation.
How to:
- Cut a thin piece of plywood, or as you can see, some random piece of thin plastic will work too.
- Mark the outside perimeter of the thin plywood or plastic, and then cut a shallow mortise for it to recess into the door frame. Position should be centered front to back of the door. When cutting a mortise, the flat side of the wood chisel should always be toward the side where material is not being removed.
- Measure the height and depth needed for the sensor and mark inside of the shallow mortise so you have lines to follow for the deeper mortise you'll cut for the sensor.
- Drill holes to remove the majority of the wood and then finish the mortise with your sharp chisel.
- Take the magnet out of the plastic holder it comes in, drill an appropriate size hole centered front to back on the door, and exactly at the center height of the sensor. Make sure it's just the right depth. If you accidentally drill too deep, you can slide a piece of dowel or thin piece of wood in the hole first, to take up any extra depth you don't want.
- Install the magnet in the hole and fill the end of the hole with calking to match your door color.
Lucky for me, I'm a wobbly driller and the hole isn't tight.
