On 11/20/2012 1:43 PM, Spehro Pefhany wrote:


Along these lines, what would the group recommend for a weatherproof
switch to detect that a yard gate is not closed all the way?
magnet/reed switch from a burglar alarm door/window ajar sensor.

Should be battery powered sensors with RF interface available for
security.


I missed that part of the specification.
Probably want three or more magnetic sensors physically placed
and logically connected to insure that it can't be spoofed by
a magnet without intimate knowledge of the design.
Encase the bullet-resistant box in concrete.
Probably want to put a signal into the razor wire so you can use
it as a proximity sensor. Maybe a satellite phone to call the
cops when the phone lines get cut. And a bluetooth
connection to the alarm system with an encrypted heartbeat
so it can't be jammed.
Probably want at least one guard dog with a wireless heart rate
sensor just in case they get put to sleep.
Of course, destroy all documentation and eliminate everybody
you ever discussed it with. Crush the hard drive.
Grind it up into dust and scatter it at least 10 miles off shore.

If security isn't the primary requirement, there are lots of devices.
The Powerhouse MS13A is a X-10 wireless PIR motion detector.
You could hack a relay into that and get motion plus gate detection.
They have other alarm sensors, but I don't know the numbers.
There are devices designed to alert you when your mailbox door is opened.
Driveway occupancy sensors.
Wireless doorbells.
Garage door openers.
RF TV remotes.

And my personal favorite...close the damn gate. ;-)