Human Presence Sensors - Switching Off Lights and AC

Trouble with cheap PIR-type sensors is that they need to be able to be set to a very sensitive level. I've worked in a place where the site electrician installed a PIR device to kill the lights when no-one's there - trouble is if the occupants are still (sitting reading, watching the PC screen etc) for a while, the lights go out. It's quite irritating, after a time, having to wave your arm around to get the lights back on every few minutes.

Now that rings a bell so to speak! Even worse when the PIR is inside the entrance to a public loo and you are inside the cubical! No amount of waving will turn the buggers back on!

Yep, been there, done that.

One place actually caught all this arm-waving on a security camera ... pretty comical ... I wonder if it is somewhere on YOU TUBE

In one other instance, I was in a place where the sensor was set too high, and throughout the off-time, whenever the ventilation kicked on, just a little shuffle of paper left on someone's desk, made the whole place 'wake up'.

There IS a better idea, using all available materials and technologies, but I'm not sure if it is affordable or if anyone is doing it ... RFID.

I've wondered why not issue badges with an RFID tag (actually ours have it now, but they're only used for door entry) and have the room, or the entrance to a room log folks in and out. This would also work to know where staff is at the moment ... not invasion of privacy stuff, but to know if someone is on-site or not, to to know if someone is 'in the shop'.

Just a thought ... always sounded like a cool idea to me.

An old computer can make a nice control unit. By multiplexing 4 input lines of a Centronix / printer interface 32 up to 1024 sensors can be monitored.

PIR sensors detect movement and as said will give "false alarms" if used to detect no movement.

Magnetic sensors (normally used at doors) installed in the seat of chairs may solve this shortcoming.

Beams, in/out counters, snore detectors, limit switches, EKG sensors etc may also help.

RFID tags may be the way to go. One can even do TV channel control.