Subject:
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Re: electronics question please help
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Tue, 23 Feb 1999 15:22:24 GMT
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Original-From:
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fthompson9@aol.com&IHateSpam&
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Viewed:
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1127 times
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In a message dated 2/22/99 6:07:04 PM Central Standard Time, noyau@apple.com
writes:
>
> My version is working but is *way* too sensible: it detect an obstacle from
> at least a couple of meters away ;^). I tried changing the two resistances
> controlling the LED output to something bigger to limit the current going to
> the LEDs with no noticable changes in detection range. Any suggestion to get
> this thing less sensible would be appreciated.
I don't think "Less sensitive" and "Sharp IR detector module" go together.
When they designed that module, their goal was to make a device as sensitive
under all types of conditions. It compensates for changes in ambient light
and in flashing IR light levels. The goal being to detect a remote control
signal from anywhere.
If you wish to detect objects at a certain distance (say a meter), I suggest
you try triangulation. First build a box for the Sharp IR detector module
which has a hole in it. Place the Sharp IR detector module a few inches from
the hole so that it can only see a narrow cone of space. Place your flashing
LED in another similar box so that it can only illuminate a narrow cone of
space. Then arrange the two boxes so that these cones of space intersect at
the location that you wish to detect objects. You could place several LEDs in
the box to make different angles, then sequence through them to detect
different depths.
Using this system the LEDs could be brighter to compensate for objects that
do not reflect IR well, but the depth to detection remains the same.
Good Luck
Pherd
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