Newsgroups: comp.robotics
Path: brunix!sgiblab!sdd.hp.com!vixen.cso.uiuc.edu!howland.reston.ans.net!math.ohio-state.edu!jussieu.fr!univ-lyon1.fr!zaphod.crihan.fr!warwick!uknet!pipex!uunet!hearst.acc.Virginia.EDU!maxwell!gr3k
From: gr3k@Virginia.EDU (Gregory P. Riddick)
Subject: IR Sensors
Message-ID: <1994Feb13.230454.16438@Virginia.EDU>
Organization: University of Virginia
Date: Sun, 13 Feb 1994 23:04:54 GMT
Lines: 30

I'm using the Sharp IR modules and wondered if anyone had tried
to modify them to operate with different carrier frequencies.
Karl Lunt mentioned in his last Nuts and Bolts article that it
looked possible, and I agree. There are what appear to be 2 SM
caps and 1 resistor inside the casing.  They can be easily
removed with a soldering iron.  Replacing them with different
values could conceivably change the operating freq. 
  Failing that, there are a modules available in 2 other
different frequencies. A previous posting mentioned that a N.C.
company sells a 38 khz unit and I think Digit-Key sells a 32
khz module.  I'm currently using five of the 40k modules in a
semi-circle around a 2 foot diameter base.  The modules are
about 2 inches apart and 15 deg. rotated from each other, and I
don't have too much problem with interference as long as the
LED emitter strength is kept low.
  Lastly, if anyone is trying to use the modules for serial
communication and object detection, I have found that a
low-pass filter placed on the output of the modules will make
my TV remote ineffective in turning them on. (W/O the filter,
the remote will activate them from at least 20 feet away). The
circuit I used looks like this:

      ____
     |    |                   100 uf     1k
     |____|                gnd-||+---|--/\/\/\ 
      | | |                          |       |
      |_____________________/\/\/\___|--|<---|_5V+
         module output      330 ohm  |   LED
                                     |output
                                      
