Subject:
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Re: expansion board
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sat, 15 Feb 1997 20:47:39 GMT
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Original-From:
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Matt Harlan <mjh10@cornell.eduAVOIDSPAM>
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Viewed:
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1338 times
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I too have used a similar technique. I used a 555 timer and a 567 tone
decoder instead of a PIC. Using an IR can from Rat Shack, and five
ir-LED's I get a sensor that sees straight ahead, 30 degrees and 60 degrees
to each side. Set the 555 for about 40kHz and the 567 for a center freq.
of about 200, although it doesn't really matter. Feed the 567 freq. to the
reset on the 555, and you've got a perfectly matched, modulated 40khz
carrier for the IR detector. The 555 output goes to the anode of all five
LED's. Simply ground one of the LED's and you can sense in that direction.
Sequentialy turn each LED on and you can sweep through the sensor field of
vision. Adjust the current to the LED's and you can adjust the range from
several feet to a few inches. Could even used a different resitor for each
LED. Longer range on the sides.
I have a PCB pattern for the sensor if anybody wants it.
FREE OF CHARGE
> > If it makes
> > it through 5 or 6 of these random on/off cycles, I count it as a
> > valid reflection detected. I thought I would have to play with it a
> > lot to make it reliably detect its own transmissions and ignore
> > outside IR interference, but it works flawlessly so far. It *always*
> > sees its own reflection, and has *never* falsely triggered.
>
> I can vouch for this technique, this is basically what I do in my
> PIC program (except the randomness which is a nice touch BTW) and
> get rock solid detections. When the frequency is spot on to the
> center frequency (38Khz for the 1ISU60's) and using 100 mA drive
> current into a Radio Shack hi-output LED I can detect walls at
> 8 feet! Using 33mA I get a nice solid detection at 3 to 4' with
> only flat black items getting down to < 1'. I use this system
> on my Wild Cougar robot quite successfully.
>
> --Chuck
later
matt
_______________________
Matthew J. Harlan
Cornell University
Electrical Engineering
mjh10@cornell.edu
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Message is in Reply To:
 | | Re: expansion board
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| I used the one available IR LED driver on the HB to drive a Radio Shack high-output IR LED. This, along with a Radio Shack IR decoder module (a little silver box about the size of a sugar cube that takes +5vdc and ground, and outputs a TTL level (...) (27 years ago, 14-Feb-97, to lugnet.robotics.handyboard)
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