Re: IR proximity detectors In lugnet.robotics.handyboard, Andrew Walker writes:
>  I'm trying to set up either one or preferably two near infra red proximity
>detectors. I'm wondering whether the sharp IS1U60L component mounted on the
>handy-board is suitable for this type of application.
[snip]
Andrew,

  Take a peek at http://www.verinet.com/~dlc/botlinks.htm and bonk on the IRPD
project.  Getting IR demodulators to work reliably is a bit more tricky that
just looking for a bounce.  I have done a LOT of work in that area and have
found that you really need to take into account the background noise to get a
reliable "hit" rate.  On that web page is a schematic and PIC 12C508 code for
implementing a self-contained IRPD using the big ugly metal can GP1U58Y style
IR modules.  The IS1U60 will work too, but, believe it or not, the +5 and
ground are swapped with respect to the GP1U modules!  Also, the spec sheets
note the use of a low-pass filter made from a 47 ohm resistor and 47uf cap on
the +5v power line - you MUST use this or the darn thing is flaky.  Another
problem with the IS1U60 is the transparent case.  In every instance where I
have used the IS1U60 I have had to paint flat black (or gray) paint on the
sides, top and bottom to prevent stray IR bounces from triggering the module.

  Also, Fred, you can sometimes (depending on the IR module) get reliable
relative range finding from these modules if you check for a "hit" after every
pulse sent out on the LED, or count the number of times you read a "hit" while
you are pulsing the LED, the return bounce is often proportional to the
distance from the object reflecting the IR.  This is the digital method of
range finding corresponding to the analog "hack" of the GP1u58Y modules that
was so popular last year.  You have to take into account the integration delay
of that particular module.  I have found that the GP1U modules and the LiteOn
modules have about a 200us delay from when they start seeing the pulses to when
the detect line flips low.

Food for thought!
DLC

