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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Sun, 23 Feb 1997 05:25:19 GMT
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Original-From:
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Richard Vannoy <richardv@(spamcake)abac.com>
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Reply-To:
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richardv@abac.com/Spamcake/
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Viewed:
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2471 times
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> Is there anyone out there that can explain programming IC for IR collision
> avoidance.
I'm sending this to other members of our robotics team because we JUST
mastered wall-hugging IR this week. They may have other things to add.
> I have read the mobile robots book and everything in the IC
> manual I downloaded and the 6.270 hardware info but still haven't got a good
> grasp of the best approach.
Here's the pseudo code:
Start
Any bumpers hit?
YES - Execute the back up, turn 90 degrees left routine.
Read the IR sensors.
Front IR sensor have contact?
YES - Execute "Wall ahead, take a sharp left routine"
Goto Start
Right IR sensor have contact? (This one is pointed 45 degrees right
of straight ahead)
YES - (Getting too close to the wall) Turn wheel to 10 degrees left
of center to drift away from the wall.
NO - (No walls nearby) Turn wheel 5 degrees to right to start
drifting toward the nearest wall.
With IR sensor range of 2 feet, this kept our robot 2 feet from the
wall. It avoids things in the way, turns both left and right corners,
and gets out of some tight corners.
> I have got a couple IR LEDs and a decoder I got
> a Rat Shack. I have tried a Phototransistor with an IR LED but the
> sensitivity was really unpredictable, with hardly any range. I was wondering
> about programming the IR out to pulse an IR LED and connecting the decoder
> to a digital input but I really don't know just how.
Bad range can be many things. Here are some thoughts...
Get to a scope to tune both the transmitter and receiver to the center
freq (Ours and many are centered on 38KHz). IR will require sheilding.
Ours required a copper bed plate under the transmitter (The receiver
modules were mounted 2 inches below the transmitter.) Also, check the
output current of the IR LED. We found that 1 mA gave us a solid 2 feet
and we could adjust out to 6 feet easily.
To avoid noise while testing, build the transmitter and receiver
separately. Keep them apart till you are sure they can go together.
When we first put ours near each other, we discovered we could REMOVE
the transmitter LED and *STILL GET A SIGNAL ON THE RECEIVER*. Turns out
the output components (especially capacitors) were ringing and acting as
transmit antennas. Shielding or noise suppressors fix this.
The LEDs transmit from 180 to 360 degrees. Their splatter is terrible.
We cut off pieces of ball-point pens (like little rifle barrels) and
placed them over the LEDs. This focused the IR to a thin beam much
better.
> There is an example in
> the mobile robotics book but again I am somewhat confused. Can anyone help
> me with the hardware and code?
>
> Appreciate anybodys help,
>
> Bill Rose
> brose@ipa.net
Keep asking and learning!!!
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Message is in Reply To:
 | | IR collision avoidance
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| Howdy, Is there anyone out there that can explain programming IC for IR collision avoidance. I have read the mobile robots book and everything in the IC manual I downloaded and the 6.270 hardware info but still haven't got a good grasp of the best (...) (28 years ago, 22-Feb-97, to lugnet.robotics.handyboard)
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