I've been asked to help with security at a farm. It's been troubled by late night theft and vandalism. Several of the fields and barns involved are several miles away from the farmhouse and don't have power. The current plan is to use an Xbee / arduino combination to detect when a farm gate or barn door gets opened, and then transmit that data back to the farm house.
My question is how to power the device. What I'd like to do is to harness the force used to open the gate to power the device, I was thinking of adapting this little wind-up LED torch....http://www.maplin.co.uk/wind-up-micro-keyring-torch-353499
I figure I could remove the wind up handle and devise a mechanism whereby opening the gate turns the generator.
The plan is that instead of having an always-on device constantly monitoring a reed switch (or similar mechanism), the normal state of the device would be off
, and as soon as the door is opened the tiny generator would produce enough power to switch the device on for just long enough to transmit a single message via an Xbee board.
Whatever solution I choose needs to be small and discrete, so wind or solar power are probably out. I could probably just use a battery, but where's the fun in that? Has anyone worked on similar problem or come up with a similar solution? Does my suggestion sound feasible? I know there are pizo devices that have been used to convert movement to power to charge phones, but I've not seen anything suitable for adaption for this situation.