Hello all,
I've seen where folks put contact sensors inside mail boxes, presumably some are metal. My question is, assuming the mesh is good, will a contact sensor work inside a safe? I'd rather not place it on the outside where it's visible for obvious reasons
If so, any thoughts on which contact sensor is best?
I currently have a few Iris sensors and on doors... they work fine
Thanks in advance
Rick
Since safes will vary greatly based on build quality (and price) and mesh factors will play such a big role in the final determination, I would say that the best way to know for sure would be to try it out with one of the sensors you already have. I love the Iris sensors and I've found that have a pretty decent signal strength.
One thing you also might want to consider is using one of the sensors that allows for external contacts, like the Monoprice sensor.
This would allow you to wire a reed switch inside of the safe and then mount the radio part outside. Most safe's will have a hole in the exterior wall for securing to the wall or floor. You could run the wire through one of those. Obviously that still leaves it vulnerable to being disabled but it does allow you to hide it rather than have it right there in front of you attached to the door.
If you think about it like a tamper switch, rather than a contact (open/closed) switch it might work a little better.
I expect, without running the antenna outside the safe (vulnerability) you will not get a signal penetrating the safe while locked. But when the door is open,it may report fine. So you're not going to get a closed report on the contact reliably, but you may get an open report through.
This would be true if the OP was trying to protect from random burglary. But that could also be prevented by securing the room that the safe was in. I suspect that OP is trying to monitor if someone is going into the safe when they shouldn't be, such as another family member. Someone who legitimately has the combination but really shouldn't be going in there. For example, a teenage child. If it were just a matter of security from break-ins, if whoever is breaking in has already disabled the rest of the system, this sensor would have been disabled too, so not much help there.
That's where my thinking was going as far as the hidden sensor through an already available but hidden access point. If someone is trying to get in on the sly without you knowing any tampering to the device would give it away as easily as the sensor itself would. But I doubt that a contact sensor on your safe is going to prevent anyone from getting into it if they've already defeated your security system and are going to take the time to crack your safe.
I did one, I installed a door contact inside, but this safe had a small pin hole, so I extended the antenna with a small wire and placed it through the hole. It works, but you need some tools for that. Yes, not for burglars, it's for kids, guns inside the safe...
That's what I was thinking. If it's a combo safe, legitimate reason for the kids to have the combo.
Rick:
The safe is painted so you will have some leakage. If you were to build an RF tight room, you would use sliding contacts and conductive grease.
My guess is you will see an additional 40 to 50 dB of path loss and I don't expect there's enough link margin to bridge that. Maybe if you place a repeater as close as possible to the safe and hope it works.
Good luck.
Dan
My old ST branded Zigbee contact sensor works like a champ in my safe. No issues at all and no mods to the sensor other than powering it via USB. I have an Iris smart plug on the other side of wall backing up to the safe as a repeater.
I tried putting the coin Xiaomi humidity sensor in it but it wouldn’t stay connected. So I purchased a Centralite temp/humidity sensor and it also works just fine too.
It will struggle inside even if adjacent to another external node, and its battery life will probably be really shortened too due to lots of retries.
As you have discovered, a metal safe is an effective Faraday cage . Most safes do have a hole for an electrical wire (for a small heater, aka golden rod). You could put the sensor outside, hidden, and have the magnetic contractor inside the safe with a wire pair between the two. Would this be enough? Also, most safes are easy to drill into. (they aren't as robust as the big, heavy safe doors make them seem). Look at the UL rating to get a better idea if this is possible on your safe. A small hole for contact wires should be possible to drill if there isn't one already.
Other options would be PIR motion sensor by the safe. The Zwave and zigbee ones that I have found are all low quality junk, to be honest,. If they aren't enough you could get a higher quality motion sensor (PIR or microwave or ultrasonic) (many have dry contacts), wire it up with a small power supply and have the dry contacts connected to a normal zwave or zigbee contact switch. Expect $100+ for the motion sensor itself.,
Disagree, my battery operated devices in my safe have similar life with those in same closet outside.
@toy4rick pick a contact sensor and give it a try.
Thanks all, great discussion here 
Since I already have a few Iris contact sensors and right now, they are $12.95 at Lowes, I bought a couple more. Also installed an Iris Smart plug about 6 feet away to strengthen the mesh.... so far it's working great and the battery hasn't changed in 2 days
Thanks again for all the ideas and support
Rick
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