The detector is tuned to 40 kHz.  You must modulate the LED at that rate and
you will get (usually) 12 -15 feet of response. However, focus the LED or
detector, add more LEDs, overdrive them temporarily,  etc and you can get
lots more.

Be sure you shield the detector from stray lights. They are overly sensitive
and things like bright flourescent bulbs will make them false trigger.

For ideas on using a PIC to modulate the IR LED, look at
http://204.233.101.40/robots/brb.html - which isn't exactly what you want,
but it should get you the basic information.

Dan

----- Original Message -----
From: White, Todd <Todd.White@ANHEUSER-BUSCH.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, September 21, 1999 7:29 AM
Subject: IR beam detection


> I have volunteered to be the "special effects" person for my neighborhoods
> halloween party. What this means....automating a haunted house, really
more like
> a haunted room that's divided into narrow walkways. Because of young kids,
the
> effects will be fairly tame. A mask that lights up as someone walks by, a
blast
> of air at another spot, some sound effects. Its not practical to have
someone
> trigger these at the right moment, therefore, I will use a PIC to do the
work.
>
> Controlling the lights, air, and sound is no problem. However, Detecting
people
> as they walk by...I could use some help. I went to Radio-Shack and bought
a IR
> LED (model 276-143) and IR Phototransistor (276-145). The LED was driven
by a 5
> volt supply and 100 ohm resistor. The Phototransistor would conduct when
the LED
> was placed a few inches away, but when the LED was more that 4-5 inches
away it
> didn't.
>
> I need to place the LED and Phototransistor about 3 feet apart to sense
when
> someone walks by. What am I missing? My TV remote works from 15 feet away.
Do I
> need a different LED/Detector?
>
> Is there another inexpensive way to detect someone passing by?
>
> Any other ideas for "tame" effects?
>
> Thanks
>
> Todd