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Cheap Distance/Motion Sensor — Parallax Forums

Cheap Distance/Motion Sensor

lboucherlboucher Posts: 139
edited 2009-12-19 04:37 in General Discussion
Hi All

So i have a project in mind and need to find a component. Specifically the sensor to use.
My project is simply to turn on a light when someone steps in front of it. (Range of 3-4' max)


My requirements are fairly simply.
1. As cheap as possible, prefer <3 bucks per sensor. (I need to buy like 50, so this could get expensive quick if i use a 10 dollar sensor.)
2. It must work in the presence of background IR. (AKA 100 amps worth of incadescent christmas lights within a 60' radius.)

I have considered Sharp IR, ping, and PIR. None seem to meet my cost needs.

Any Thoughts?

Comments

  • kwinnkwinn Posts: 8,697
    edited 2009-12-18 03:56
    The sensors used in home alarm systems work well in high light/IR conditions and are more than sensitive enough. Not sure of price or how flashing lights would affect them.
  • SRLMSRLM Posts: 5,045
    edited 2009-12-18 04:09
    An IR LED and detector might work. 3' is right at the limit of it's range, but you can always test it out for cheap(since it meets your cost requirements!). According to mouser, it is about $1.30 for the receiver, an IR LED $0.20 . The main problem is that you will have to drive all of them somehow to get useful distance information.

    An even cheaper solution would be mechanical: use a switch with either a pressure plate or some sort of arm.

    Another solution might be to use a beam of light (either IR or visible) that is either broken or not. That setup would only cost maybe $0.50, at the cost of some setup and only binary distance.

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  • lboucherlboucher Posts: 139
    edited 2009-12-18 23:23
    So the application is for my christmas light display.

    Something for the kids to play with.

    Basicly a bunch of lights that go off when someone walks on the sidewalk next to them.

    So a pressure switch is kinda out, because i need like 50 and cannot put that on the sidewalk.

    A beam going across is kinda undoable, due to having to have a wire across the sidewalk.

    I agree that driving the IR myself will jack up cost, and i cannot seem to find an IR transeiver (All circuitry built in) for a low enough cost.

    Hummm.
  • HollyMinkowskiHollyMinkowski Posts: 1,398
    edited 2009-12-19 00:39
    lboucher said...
    A beam going across is kinda undoable, due to having to have a wire across the sidewalk.

    Put a reflector on one side to bounce the IR back to the sensor on the other side...no wire.
  • lboucherlboucher Posts: 139
    edited 2009-12-19 04:37
    Ahh, i follow ya now, but still, i just see things getting stepped on.
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