The Naked Scientists

The Naked Scientists Forum

Author Topic: Can lights be controlled to turn them on and off when a person enters or leaves?  (Read 3482 times)

Offline mommylady28

  • Jr. Member
  • **
  • Posts: 15
    • View Profile
can heat and moshion detecters be wired together to know if a person is in the room and tuirn on lights when they are there, and go off just as they leave it? like the light from a plasma globe atracting to the glass where it is touched? and know the difrence between a dog and a baby

« Last Edit: 14/06/2012 09:31:38 by chris »


 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Re: plasma lights that shut off when a person leaves the room
« Reply #1 on: 30/05/2012 05:49:06 »
Motion detectors, of course, are often used outside, often with a timer.  They are often a bit of a pain because if the motion falls below a threshold, they will shut themselves off, and you end up waving your arms madly to get them to turn back on.  So, settle down to watch the tube or read a book, and the lights would go out.

Hmmm, this seems to indicate a passive infrared motion detectors  It would seem as if the circuitry could be designed to keep active when the target temperature (98F to 99F, or thereabouts) is present.  However, it may actually need a higher resolution sensor, as well as it may essentially generate a scene average temperature. 

I could imagine taking an IR filtered CCD with a wide angle view, constantly scanning for human sized objects around 98.6F. 

A large dog would likely trigger it too.  Maybe an infant.  Is that desired?  A smart system would be maskable.  Yet, one may end up expending more energy on the circuitry than what would otherwise be saved without the sensor.  What about clothing and varying ambient temperatures?
 

Offline mommylady28

  • Jr. Member
  • **
  • Posts: 15
    • View Profile
Re: plasma lights that shut off when a person leaves the room
« Reply #2 on: 31/05/2012 09:07:34 »
yes scaner, that is on a timer. no detecter. yes baby. smart chip in pet tuirns off light when no people present. use energey colected in the house, from every door opened, sun, wind,
 and rain watter in gutters? can we make the butterfly efect work with energey?
 

Offline weirdscience

  • First timers
  • *
  • Posts: 3
    • View Profile
i would think something like those beams that stop garage doors from closing if the path is broken would work. when they're crossing once the lights go on, when they're crossed again they go off. of course this would become much more difficult in a room with multiple entrances
 

Offline crimsonknight3

  • Jr. Member
  • **
  • Posts: 42
  • Thanked: 1 times
    • View Profile
Bill gates had a slightly easier solution. He carried with him a device (pen or phone or something i cant remember) using gps, it knew his exact position in the house and thus using a little programming, could predict what room he was entering and turn on the light and when leaving turn it off, this would be easier than installing a lot of sensors, however it could be a pain if you forget your device lol he could also send a message to his house telling it to turn on the coffee machine and run a bath while he was on his way home, id LOVE that!
 

Offline techmind

  • Hero Member
  • *****
  • Posts: 934
  • Un-obfuscated
    • View Profile
    • techmind.org
At my sixth-form college 20+ years ago they had lights controlled by infra-red motion sensors. As CliffordK has noted, these are problematic as once the teacher had finished doing their "talky" bit and the class settled down to do some exercises, the lights would go out.
It's tricky to make an "absolute" heat sensor that would truly detect presence (and even if the sensor were ok, you need to somehow avoid false triggering from radiators or where the sun in shining on a surface and warming it up), so instead the typical cheapo PIR sensors have one sensor and a multi-faceted mirror - when people in the room move around this creates abrupt changes in the radiation seen by the sensor and it's these changes rather than the absolute temperature which keeps the lights on or triggers the alarm or whatever. Because the system only reacts to movement of warm objects, you need a timer to keep the lights on for a while after the last detection -- and the setting of the timer is always a compromise between keeping lights on too long after someone leaves, and lights going off prematurely cos someone sits still for too long.


Modern cheap cameras and image-procssing systems, including "3D cameras" such as Microsoft's Kinect are technologies that may provide better solutions to this problem in the near future.
 

The Naked Scientists Forum


 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums