Subject:
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Re: IR collision avoidance
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Tue, 18 Mar 1997 14:21:27 GMT
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Original-From:
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Sriram Tirunellayi <sriram@ds5500.cemr.wvu(NoSpam).edu>
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Viewed:
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1524 times
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>
>
> Good question! We had a lot of noise problems and learning curve
> stumbles along the way. Our first bad news was that we had a range of a
> few inches. We finally beat that one fooling with frequencies, caps,
> etc. and then found out our range was SIX FEET!!!
could u please tell me where u bought the infrared LED's? The one
that i bought from radio shack (part no.276 143) is giving a maximum range of
7.5 inches and i badly need to sense atleast 1 foot.
thanks
Sriram
We didn't want that
> either, so James (in the Cc above) had a bright idea. He put a pot in
> series with the output LED to see if he could control range with current
> and sure enough it worked! About 1 mA and he got two feet (which as
> programmer, I needed to make sure our bot could turn and avoid
> walls/obstacles). Let me see if I can draw it...
>
> |
> | A
> | / B
> | /
> | /
> | /
> | /
> | /
> | /
> | /
> | /
> | /
> -------------
> | X Y |
> | |
> | |
> | robot |
> --------------|
>
> A = forward looking IR
> B = IR pointed at 45 degrees from forward (actually NOT 45 in this
> drawing)
> X+Y = the IR transmitters located just above the receivers.
>
> Now close your eyes and imagine you are the bot. Also when you stick
> your left arm directly out in front of you that is front IR, and when
> you stick your right hand out at 45 degrees, that's your right IR. Now
> here is pseudo code...
>
> Step 1: Stick out your left hand. Did it hit anything?
> If YES, TURN LEFT 90 DEGREES RIGHT IMMEDIATELY, you are about
> to hit the wall! Skip step 2 and go on with other things.
> If NO, go to step 2
> Step 2: Stick your right hand out at 45 degrees. Did you hit
> anything?
> If YES, you are too close to the wall, so move the steering
> wheel to LEFT 10 degrees to ease AWAY from the wall.
> If NO, then you are not near any walls, so move the steering
> wheel 5 degrees to the right. This will put you in a long
> slow arc to the right until you get close to a wall.
> Step 3: Do other sensor checking and go back to step 1.
>
> Step 2 is the key! Notice what happens when you are close to the wall.
> You are either too close or too far all the time, so you are correcting
> a lot by shifting the wheel from 5 degrees right to 10 degrees left. As
> you watch our bot it seems (to someone who doesn't know what's
> happening) that it travels in a straight line 18 inches from the wall,
> but if you look close, the wheel shifts back and forth about once or
> twice a second, correcting constantly. See the wall? move away. Don't
> see it? move closer, over and over. It really comes out quite smooth.
>
> So the formula for a wall hugger is the IR range divided by 1.414 =
> range from the wall.
>
> |\
> | \ Not to scale, but hypoteneuse of a square is one
> side
> A| \ B times 1.414
> | \
> | \
> ------
> C
>
> A = distance to wall
> B = IR beam
> C = WALL
>
> If B = 2 feet, and B = A * 1.414, then A = 24 inches / 1.414
> or 16.973 inches, or as we say, about 18 inches.
>
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Message has 1 Reply:
 | | Re: IR collision avoidance
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| (...) The Radio Shack LEDs should work fine. The trick is that these things are very sensitive to intensity, duty cycle, and frequency stability. To modify intensity change the amount of current flowing through the LED (lower resistor value == more (...) (28 years ago, 18-Mar-97, to lugnet.robotics.handyboard)
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