"Remote" activate a device?

Hi, I’m creating a device that will be self contained and sealed. It only works at night so if you package it in a box it will work, which ideally it should not. It cant have any buttons on it nor should a person unseal it to activate it.

So I was thinking of putting some soft of RF, Bluetooth, NFC, [insert wireless technology here], which should be super super cheap to activate it, the less the distance the better. Device would be powered and hibernating but the active component would work once activated remotely.

Can anyone suggest something and have you had such requirements yourselves??

Thought of capacitive touch switch?

@ Darko - IR receiver?

@ RobvanSchelven -

how would that work? maybe forgot to mention that only the person who installs the device can activate it, but after persons walking buy should not be able to mess with it, hence why it is sealed.

@ devhammer -

never worked with IR how is that security wise? also the device is encased in 4mm aluminum so I would need to expose it?? im currently exposing one photo resistor with a LED lens.

@ Darko - Since you have a metal housing capacitive is not a real option. Here’s the idea


Google on “capacitive touch”

Well, IR simply needs the receiver part exposed, which is pretty small. Upside is you could define your own protocol for the power on command, and it would be very difficult for someone to reproduce it without capturing the original command when the device is being activated. In order to do that, they’d need to be aware that it used IR, and they’d need to be present (or have their own IR receiving device present) when your command is issued.

I think the two downsides to IR are that it requires line-of-sight (though you can sometimes get around corners if the IR light bounces enough), and it’s subject to environmental interference, primarily from sunlight (IR is not very reliable for outdoor use) and some types of fluorescent ballast. For a simple on/off command, this is usually not a major problem, but the scenario I’ve used IR for is controlling hobby helicopters, so interference becomes a lot more significant in that situation. :slight_smile:

BTW - if the device is somewhere that a potential attacker can reach the device, whatever you use to activate it is irrelevant…with physical access, a determined attacker will own the device.

Would need more details to give any better answers from a security standpoint. Lots of variables there.

Initially thought RFID when I read “the less the distance the better” but then you talk about activating remotely which kind of blows RFID out the water.

ok, touch is out, it will be outside so IR is out, and the term remote may be incorrect, an activating device could be just 1cm away. so RFID? does that work with 4mm aluminum? what do I need IC wise? and what kind of control device would I need to create.

id prefer IC parts and not ready made modules, I can make my own, needs to be super cheap

its unlikely any radio based signal will work thru 4mm aluminium plate. This seems a very complex ask that you may find nobody here has any experience in, so anything you glean here may simply be guesses

A read switch might be an option. Using a magnet to activate the device.

No I don’t think RFID will not work through 4mm aluminium. The metal cladding pretty much excludes all RF methods.

Could you include a perspex/GRP window in your enclosure?

Double negative there - I think you just mean RFID will not work thru Alu. A Perspex or similar window might not be a bad idea to get around that, obviously it does increase risk of water ingress as you have more edges to seal.

I still don’t quite get the need. Is it necessary to be “stealthy” in how it’s activated, for example is the fact that it uses RFID (and you can see the reader thru the “portal”) an exposure/attack vector you can’t have ? Would having multiple touch points in different areas on the casing be simple enough, but obviously it could be “worked out” by someone. Do you need a two-factor method (something you know, something you have) approach where you shine an IR “beam” using a custom “controller” implementing the magic handshake protocol of your choice/invention into a less-than-obvious location going to work ?

But as many have pointed out - physical access trumps everything. If someone with a screwdriver or a dremel wants to see what’s inside a 4mm aluminium plate box that’s lying somewhere, even hidden, I am sure they can achieve that

As my wife always tells me - I can’t multitask! :-[

1 Like

Acoustic activation; Ultrasonic clicks

@ Mr. John Smith - YES, make it activated by a bird call!

@ MRTFEREN - Did you have a specific bird call in mind ? :slight_smile:

@ Mr. John Smith - A loon of course. It looks like this :whistle:

@ Darko - How complex does the communication need to be?