Smart-Key for home

Dear colleagues,

I was thinking of developing a new project for home, but I need a little guidance.... I'm trying to make a home security system that will be activated when a "smart key" is not in range of an arduino let's say. (something like smart-car-keys). Is it possible? What kind of arduino shield or "smart key" would I need?

Warm regards,

that will be activated when a "smart key" is not in range of an arduino let's say

If you really intended the word "not" it makes your requirement rather strange. Can you explain further?

There are millions (maybe billions) of ways for a smart-key NOT to trigger something.

And an important point about any smart-key for access to your home - make sure your insurers approve, otherwise it may invalidate your insurance.


Dear Robin2,

Thank you for your post.

Yes, I've misspelled that phrase, I want the alarm to be active when the key is not in range. I was thinking I can do this system with a RFID setup, but that means that the key (key-chain) must be in a specific place (on the RFID reader) for the alarm to be deactivated, and not be there for the alarm to be active.

That would be a simple solution, but I would love it if I could somehow make a system in which the key needs to be "in range" (4-5 meters) of the microcontroller or receiver for the alarm to be deactivated.

Already checked with insurers, and its all OK :).


If I understand it correctly you want an alarm system that deactivates automatically when you are near or inside the house without specifcally switching it on or off by holding a RFID tag near a reader.

I get the impression that the new Bluetooth Low Energy system may be able to do what you say. You may find this Thread interesting.


Hmm, very interesting thread Robin2, but, I was thinking more at creating a project with a Bluetooth module for arduino (HC-05), and buying a bluetooth key and pairing them somehow.

I’ve found a tutorial for pairing 1 bluetooth module, to a smartphone, but that isn’t quite what I need.

I wounder, can you pair a bluetooth module to another bluetooth module, and then transform the second module into something that someone can wear on their key-chain?

Also I’ve found this.

AFAIK you can pair two HC05 modules.

You will need to satisfy yourself that your system cannot fail by losing a connection (perhaps due to inteference) while you are in the house and switching the alarm on when you don’t want it on.

I suspect you would need BLE if you want the low power consumption that a key-fob battery system would demand.