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VERY Short-range PIR Sensor

Former Member

I am looking for a VERY short-range PIR Sensor.  I am looking for a PIR sensor which ONLY detects motion within a range of about three inches (3").  I want to make a light switch for my daughter's closet which responds to waiving my hand in front of the sensor --- waive a hand in front of the sensor, and the closet light goes on; waive a hand in front of the sensor again, and the light goes off.  This is to replace the regular standard togle light switches you find in most homes.  The reason I want to do this, is that my daughter, often, leaves the light on in her walk-in closet.  I want to connect a PIR sensor INSIDE the closet to turn off the light when no one is in the closet; however, if I do that with a standard togle, light switch, the switch will be in the up position [ON] when someone comes back to turn on the light again.  So, if I replace the standard togle, light switch with a small PIR sensor (which responds to a waive of a hand over the sensor), the light in the closet will go on when someone waives their hand over the short-range PIR sensor [I should mention that the light switch for the closet is on the OUTSIDE of the closest -- before one enters the closet].  Again, to activate the switch, I want to waive my hand over the PIR sensor.  Then, the light will go on.  I will have another standard PIR sensor INSIDE the closet which will turn off the light if no one is in the closet for a specified amount of time.  Then, later in the day, when someone wants to turn the closet light on, they just have to waive their hand in front of the PIR sensor located on the wall outside the closet; and the routine will repeat itself.  The PIR sensor on the outside of the closet (to turn the light on) has to be VERY short-range so that it doesn't pick up any of the usual motion in my daughter's bedroom -- again, just long enough (and ONLY long enough) to pick up a waive of the hand in front of the sensor (3-4 inches).  I am going to wire the OUTSIDE PIR sensor so that a waive of the hand will turn the light ON or OFF depending on its status (already ON, or already OFF).

Thanks for your input!

Richard

  • 0

    Hi Richard,

     

    I am not sure a PIR will do what you want.

     

    I would go buy one of the battery powered lights with an IR detector.

    It detects when you put your hand close to the device and turns on an LED light.

    It then times out and turns the light off.  If you need more time, you just wave your hand in front of the sensor again.

     

    This type of switch is readily available and would easily serve your needs.

     

    DAB

  • 0 in reply to DAB

    DAB,

    I appreciate your input.

    I was thinking I might want to use my original concept (with a PIR sensor on the wallplate) in other places throughout my house -- thus, the battery-powered light would not be feasible.

    I was just realizing, however, that if I tried to use a PIR sensor on a wallplate that had more than one switch (and, thus, more than one PIR sensor), a waive of the hand might trigger more than one senor and more than one switch; thus, I would need to limit the sensitivity to just one sensor/switch (which, I presume, would be impossible to do with a PIR sensor).

    So, I think the solution is more-than-likely a push button switch (or, at least, a touch sensor switch); in this way, there could be more than one switch on a wallplate, and each switch would be activated individually.  This would, also, solve the problem of having the standard toggle switch left in the ON position (when the PIR sensor inside the closet turns the lights off).  The touch-sensor switch would not have any ON or OFF setting.

    That said; I, still, need a VERY short-range PIR sensor for another purpose.  I put my glasses on my dressor late each night before I go to bed -- ususally, after my wife is asleep.  I don't want to turn on the lights.  So, I was thinking that I would put a very short-range PIR sensor on the top of my dressor which would activiate some LEDs to briefly light up the top of my dressor.  I would want this sensor to activate ONLY when I put my hand over the top of my dressor (NOT when I walk by my dressor).  Thus, I was, also, looking for a very-short range PIR sensor for this purpose.

  • 0 in reply to Former Member

    What about a photoswitch? Contactless, short range.

    This one is a bit expensive, but cheaper options are available:

    Farnell article 731481

  • 0 in reply to vsluiter

    As I understand, a photoswitch would turn a light on when it is dark.  I only want the light to come on for a few seconds only when I am near my dressor top -- so, I don't want the lack of light (a photoswitch) to trigger the light, I want my movement over my dressor to trigger the light.

  • 0 in reply to Former Member

    The way we've done this sort of things with robots for obstacle avoidance was a simple IR LED and a phototransistor both pointed the same way. Not enough light is reflected back to the phototransistor unless you've got something a few inches from it. So waving your hand in front would easily trigger it. Its also 'dark' for humans so you don't see it when the lights are off (its infrared). For low power applications it is possible to have a micro wake up 4 or 5 times a second, check the transistor and go to sleep. Very simple to do. The Atmel 'sleepwalking' demo would be ideal for that app as it uses like 20nA when its asleep so you could run this for a couple of years off a couple of AA batteries.

  • 0 in reply to Former Member

    Hello Richard,

     

    The article I linked to, and also the kind of setup Chuck refers to is simply a light-sending device and a light-receiving device (preferrably out of the visual spectrum, and using a small cylinder around it to prevent direct sunlight entering). When you keep your hand in front of it, light is reflected into the light receiving device, and you can switch something on or off.

    The article I linked is an all-in-one completely engineered solution, simpler alternatives are found in many applications. Take a look at this devicethis device and this thing at Sparkfun too!

  • 0

    Greetings,

     

    Have you concidered reducing the sensitivity is the PIR or a shield to limit its field of view?

    Or possibly a capacitive touch circuit connected to any metal object on the desk. I use this alot for hidden (magic) switches.

    - Steve

  • 0

    I guess this thread is dead but for reference, PIR have a wide view because of the plastic cover that acts as a frensel lens remove the plastic cover and you have a single direction PIR