Instructables

How can I install motion sensors for the lighting in my room?

I would like to have a motion sensor in my room that would turn on my ceiling lights and last for an hour.

benefits: Never forgetting to turn the lights off, not wasting time in my room, taking breaks from computers and saving money.

rickharris3 years ago
Difficult I think - As once in the room you would need to put motion detector to sleep for an hour and then check if there is any one still in there to retrigger for the next hour.

I think coulting people in and out might be easier AND you only have lights on for the time people are in there.

Also need to monitor ambient light to know if it is dark enough to need the lights on.
I think this is a job for Microprocessors.

Isn't there a UK professor who had the equivalent of a dog RFD chip placed in his arm and wired his home and school's computer lab to keep track of him a decade ago ?
He, would have no problem activating bedroom lights :-)
I wonder is he still radiating ?

Postmortem a body in the ground would still be able to radiate :-X

A
Yes there was he had it removed though due to an infection issue.
That is / was a shame thanks for the pointer, though Wikipedia dos not mention what I consider necessary knowledge about said infected removal.
Apparently Kevin Warwick had a second implant of neural nature that was
well accepted by his body.

Thank you for your help.

A
orksecurity3 years ago
Motion detectors is relatively easy. "Last for an hour" is a bit more complicated; you need to have each "ping" from the motion detector (re)set an hour timer. You'd need to pick a motion detector technology -- IR? Ultrasonic? Camera?. The timer is relatively easy; I _think_ a 555 can be configured to run about that long, and if not there are lots of other approaches. Then it's just a matter of having the output control a relay which can handle the current you want to control.

Note: This will be MUCH easier to homebrew if you make it control desk or floor lamps rather than trying to wire it in place of a wall switch. Probably safer too.


The problem is, there's an awkward tradeoff here. If you're sitting at the computer (or watching TV, or reading) for an hour, not moving much, the lights are likely to go out -- unless you make the detector sensitive enough that cats and winds blowing curtains and that sort of thing are likely to turn it on. On the other hand, on average you're burning the lights 30 minutes longer than if you just got in the habit of turning them off as you walk out the door, PLUS burning the power for the motion detector itself (not much, but a bit), PLUS having spent the money for the motion detection/timer/relay circuitry.

This sort of thing may make sense in a business setting, where people really are complete slobs about not turning off lights. But even there, having a human turn off the lights when they're the last one to leave the room saves a lot of power. My office had the commercial version of this, and I spent a lot of time getting annoyed with it and manually turning off lights.

I've pondered the idea myself, but came to the conclusion that motion detector really wasn't going to do what I wanted. A dual-beam counting setup at the door(s), which tracked number of people entering/leaving the room, would be closer to my own needs -- lights go on automatically when the first person enters and off immediately when the last leaves -- though there will be periodic counting errors that will have to be reset. One nice thing about the occupancy counter is that it can be installed at a height where pets really can't trigger it.
FYI You're really pushing a 555 to get an hour from it !! I'd have to say use a digital counter these days. At one point, there was a 555 with an integrated, adjustable, divider chain in it, but if you have to use a 555 and you make it time for say a 1/4 second, and add a divide by 2^12 stage after it, you end up with about a one hour delay.
Valid point re the limits of the 555; I really should have rechecked the spec first.

Digital divider with the 555 being used as a clock circuit is certainly a good option; you'd want a couple more gates so it stops counting when it hits the timed-out state and can be reset by the motion detector to start the count, but that's easy enough to do.
Mylar helium filled balloons can drive motion detectors crazy, especially when the air conditioning kicks on and the motion detectors trigger your burglar alarm system. Repeatedly.
Been there done that. lol