All contact sensors that I know of that work with smartthings use magnets, so they all have the same potential issues with metal doors. That said, since you’ve already raised the sensor up onto an onto a wooden block (both parts of the sensor, right?) , you’ve already done the main trick for avoiding this problem.
So next I would consider two possibilities.
- is the radio piece on the same side of the door as the hub? sometimes a metal door is just too hard to get signal through. This is one of the few situations that can lead to a door sensor never being marked is closed. The reason is that the signal from the radio gets through when the door is open, but can’t get through when the door is closed, so the hub never receives the closed signal.
However, if that’s the problem, then it should be happening almost every time, not just intermittently.
- I think it’s probably more likely that this is just a typical smartthings platform issue that many people report and has nothing to do with the metal door. States just don’t always get updated.
(BTW, this problem is amplified for Z wave if you have any zwave energy reporting devices. But that’s a separate discussion.)
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If it is, in fact, a problem with the door becoming magnetized, the following post I wrote in 2018 does discuss what commercial buildings do about this issue:
Back to the original problem… If the door is normally kept closed one thing that some offices do is to put a very strong magnet piece on the wall and the sensor piece on the door in such a way that once the door is open about 6 inches, the magnet is strong enough to pull the reed inside the sensor into position. But because the magnet is normally kept away from the metal door, you don’t have the usual problem of the magnet magnetizing the metal of the door itself, eventually causing false readings.
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This works best with doors that have a doorstop on the wall as well so the sensor pieces can’t get crushed by the door opening.
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In your typical door sensor, the smaller piece is just a magnet in a fancy box. You can replace it with any other magnet, including one that is much stronger or weaker if you want to try to adjust the detection distance.
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So that is something which is done in commercial buildings, move the magnet off the metal door all together but is a much stronger magnet so you can cover about a 3" Gap rather than the typical half-inch gap. You’re still keeping it away from the metal door, but you should catch the open event before it’s wide enough to let a person through. Just another option to consider if it works aesthetically for you.
But that would be more commonly used for a door sensor that was reading closed all the time, not one that’s reading open all the time. Still, it’s possibly true that a stronger magnet in a different position might help. But I think it’s more likely one of the two issues I described earlier in this post.
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Another alternative if this door has a doorknob with a regular latch/bolt is to put a microswitch inside the wall to detect when the bolt is present. That doesn’t rely on a magnet.
People more commonly use this to determine whether a door was manually locked, but it can work in the kind of situation you describe, depending on the exact details.
There’s a discussion in the following thread starting with the post I will link to about how one community member did this to determine if his door was locked. The thread itself from is from 2015 and is obviously out of date (for example, it refers to shopping at RadioShack) but the basic concept would still work. You need to have something which is physically different when the door is open or closed and you need to have a place to put the microswitch that measures that contact. But it does avoid the magnet issue.
Home made door lock sensor - #7 by johnconstantelo
(Note that the Aeotec recessed door sensor doesn’t solve the problem because it also depends on a magnet.)
