Sensor antenna extension - Gun safe

Has anyone successfully added a antenna extension on a zigbee or zwave sensor?

I want to put something in my gun safe to measure humidity and possibly motion. But everything has been unreliable (understandable since it’s in a bit metal box). I do have a passage to run a wire, so I thought about soldering a length of wire to the antenna pad on the board of a device to see if that gets me better range.

Changing the antenna length changes the frequency efficiency. So that doesn’t work.

Instead, what you want to do is get a probe that can be attached by wire to the Z wave device outside the box. That’s what people frequently do for freezers and for ponds. Works fine. :sunglasses:

(The topic title is a clickable link.)

Thanks to @paul_haskins below for the correction. I’ve updated this post. It’s not the frequency itself that changes, it’s the efficiency of sending and receiving messages. But that can really mess up your network. so the same point to be made, just for a somewhat different reason.

Ie, extend the actual sensor.

I guess the trick is resoldering and messing with the surface mount components just about everything has.

Another dumb thought was using zigbee. I had a sensor that worked but would occasionally miss a heartbeat and fall off the network. I never thought about adding a repeater directly next to the safe.

I think that may be a really good option for you to try. You can rejoin the sensor while being close to that repeater to ensure it uses it. I have zigbee sensors in 3 frigs and 3 freezers, and while not like a gun safe, there’s still a lot of metal and other interference to go through. I have repeaters super close to these sensors, and I have yet to have one fail or drop. It’s been 3 years at least since I’ve put these sensors in my environment :wink:

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Changing the antenna length will not change the actual frequency of any transmitter. It may not be as efficient (signal strength wise), but it might work.

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Waveform matters. Because, physics. :wink:. Yeah, the transmitter itself doesn’t change, but the efficiency of sending and receiving messages definitely does. I’ve corrected my post above. Thanks!

The Centralite Temp Humidity sensor should work well for your safe. You can also put a plugin Zigbee outlet/repeater near by to make sure it has a good signal.


One note: freezers typically have a rubber seal around the topset door which allows some signal to escape. Security safes typically do not, because that would create a breach point. They have fully inset doors with a thin gasket, but then more metal on the side. So it may be harder to get signal out of a safe, in which case you go back to the probe sensor with the wire coming out to the radio device.

My thanks to @ritchierich for the clarification below.


So, you can solder onto the board to extend the antenna, but you’d lose efficiency AND you’d have to make the length of the wire very precise according to the frequency of transmission, in order to match the wavelength (higher frequencies require more accurate antenna lengths). I’d give it a go, but it’s more art than science, and you could end up quite miserable.

Not sure of the device you are intending to use, but you’ll need a cable for power going into the cabinet (and if you were thinking of having antenna wires external to the cabinet), so is it possible to have the sensors inside the box and the processor (subtly) outside (thinking nodemcu homebrew style)?

I’m interested as I’m thinking of doing the same…


Safes also have rubber seals to keep water out.

Regardless I speak from experience as an owner of the Centralite device and a safe and can vouch that it does indeed work :sunglasses:. I have a very strong zigbee mesh so YMMV


Yup, same here. Without divulging too much about my scenarios, zigbee open/close and temp/humidity sensors (mine are the Iris branded Centralite devices) work just fine inside small and large safes. I also have a very strong zigbee mesh.


Mind my asking, specifically which product are you using for humidity? Message me directly if you don’t want to post too much about it. I’m mostly concerned about humidity but motion would be nice too.

I have these in all my showers, and a few other areas where temp and humidity must be monitored:

Pretty much the same one from Centralite that was posted above, but just branded by ST.

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Good point, I should have said thick visible seal around the top set door. The most important point about that is that there’s rubber in all directions. Gun safes will typically have a thin seal around an inset door, so that more signal will be blocked… That’s what I meant by “around the door“ but I realize it’s not clear if you aren’t looking at a picture. I’ll edit my post above, thanks. :sunglasses:

But as always, you may be able to find a place where it works. As a former field tech, I always have a bias against big metal boxes. :wink:

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Well drats, the old ones. I was hoping they still offered them.

I wonder if the new square Aqara sensors are any better than the original Xiaomi sensors (round) I bought from China. I never had any luck with them staying connected.

I tried Aqara too and it never stayed connected in the safe. The Centralite I posted link to above is the same sensor @johnconstantelo posted. They were available on Amazon within the last year but no longer try directly on their website.

Another option which I have also used is @iharyadi Environmental Sensor though not sure he has any available:

Nice with it is you have other inputs to use as a contact sensor too all in one device.

It looks like the newer version might be available directly from Centralite.

Interesting about the Zigbee repeater solution. Just skimmed the thread and bookmarked it for later reading.

Another thought is the Zooz ZwavePlus motion sensor which does humidity. I’ve always seemed to have better range with Zigbee devices, but 900mhz theoretically should penetrate walls better. Perhaps again if I had a ZWP repeater nearby…