For reasons of general sensibleness and security I won’t go into much detail about exactly how my DIY Alarm Bell Box is configured to work in relation to actually keeping thieves away. Just a reminder that it’s always best to get help from Electronic Manufacturing Services for projects like this. Suffice to say: network of sensors indoors and out, differential siren sounds depending on alarm state, iPhone notifications and emails to neighbours (seriously, I will be doing the same custom install for them, they are very nice people. And big. Very very big. 7 foot. And they have dogs. Dogs that eat anything.)
So the thing pictured below looks like a dummy box, it’s sold as a dummy box, but it is far from a dummy box.
It’s sold on eBay for £9.10 including postage from a UK seller (that price is without “dummy LEDs” – I’ll be adding my own thanks), and it does rather fortuitously have a rather sophisticated plastic moulding design inside that allows the placement of alarm sirens, LEDs, internal housing boxes, and incoming cables.
£9.10 including postage
The box itself is not IP66 rated, but that’s not a problem because I have bought from Maplin an internal component box and some anti-mould silicon sealant which will do the job of making sure the electronics I’m about to pimp this thing up with stay nice and dry.
So what’s going into this puppy?
Arduino Nano, obviously. And a tiny red W5100 break-out board to provide networking. Oh and this cool super-tiny buck converter to allow me to power the thing over ethernet:
And the cool stuff? Why not:
- Vibration sensor (for anti-tamper)
- BMP180 Barometric pressure sensor (we always need to know outdoor pressure, right?)
- BH1750FVI Ambient light sensor. This is mounted under the blue window, but it doesn’t matter because the serial output needs calibrating to some kind of meaningful scale anyway, so it’s all relative
- DHT22 Temperature and Humidity sensor. Because it’s wrong not to
- 4x ultra-bright red LEDs
- 4x ultra-bright blue LEDs
- 4x ultra-bright green LEDs
- 2x cheapo very loud buzzers (Maplin and eBay – £2 each – different pitches)
The astute amongst you will notice I’ve already maxxed-out the pins on the Nano, but LEDs will be in groups of 2, meaning 6 pins. This still gives me Knight Rider options. More importantly it allows me to use a number of signals to would-be burglars.
I may even use these addressable LEDs with driver, if I can be bothered not to program individual LEDs myself.
Naturally the thing will report sensor values on their own individual MQTT topics back to my OpenHAB server which stores all data for historic purposes.
And naturally the thing will respond to commands such as:
- Make discreet but audible warning beep to potential intruder in back garden when house armed
- Make screaming noise when house security has been compromised (this of course along with iPhone notifications / emails sent to me and three other nominated contacts. I’m lucky, I have cooperative neighbours who will take care of these things)
Such commands will be triggered in OpenHAB from network of sensors inside and outside the house, including vibration sensors on doors etc.
Will I get a twitter notification when a cat / dog / fox moseys into the back garden? Probably.
And the fun stuff:
- Using a series of fun flashing sequences, alert me when I walk down the road whether wife, child, or both are home. (FYI I’m not really married.)
- Using a series of fun flashing sequences, alert me when I walk down the road that I should have brought an umbrella as the forecast shows it’s going to rain in the next 4 hours
- Using a series of rather serious and angry flashing sequences alert me that I left the window open when I left the house