Light detection

[CAD Monkey]

I'm looking where to start for a prank project. I'm needing to rig a flash light so when a person walks into a certain area, it automatically turns off till they walk out of that area.

Back ground of me.... I have no knowledge of electronics... I would LOVE to learn so that I can get the tons of projects in my head out. Any general idea of what I need to learn or where to learn it from would be appreciated.

Thanx

 

[BobK]

Is the person carrying the flash light? How accurate should the boundaries of the area be? Are you talking about whole room or a specific area in a larger open space?

Sounds like a good Halloween haunted house project, but I think you are little late for this year.

Bob

 

[(*steve*)]

Sounds like a job for a PID (Passive infra-red detector). Although tthe person needs to keep moving to keep it triggered (ant some PID triggers will reset anyway. but you can fix that with additional logic)

 

[CAD Monkey]

I know I would be late for this year but have an awful prank I want to play on the family. Have an abandoned house on a friend's property that I want them to walk through. If I hold the flash light they would just assume I would be doing it.

As for area, I don't know. I would hate to have it trigger in an area that I didn't want it to.

If they stop, then the light would go back on... not really the direction I'm wanting to go.

 

[iimagine]

Sounds fun!

An alternative is to use one of these cheap wireless remote+receiver module:
http://dx.com/p/mtdz006-rf-1-channel-wireless-remote-controller-switch-module-green-blue-153147

Hide the remote in the area that you would want to turn off the flash light and keep that remote switched on. Have the receiver module to somehow fit inside the intended flash light

Edit: Errr.... I didnt notice the 12V requirement....forget about this

 

[(*steve*)]

It's pretty difficult.

The problem with detecting a light from a torch is that it will detect the light from the room lights too.

One option is to have red room lights and be totally insensitive to red, so the detector never sees the room lights.

Other than that, the options get more tricky and difficult to achieve. Certainly before tomorrow...

edit: ok, re-reading it -- you'll be with them and you can point your torch to somewhere specific. That's easier, but the remote control in your pocket is easier.

There are remote controls used to turn on and off power outlets. If the light was a lamp (rather than a room light) then this would work if you can hide the remote control and the switch box. It's also something you should be able to take a trip to a shop and just purchase

 

[BobK]

An IR detector, the type used in remotes (38KHz) could be built into the flashlight such that it turns off if it sees the IR signal. Then an IR emitter could be put in the area where the flashlight should turn off.

Bob