Subject:
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Re: IR wall detection
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 16 Jan 1997 08:27:54 GMT
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Original-From:
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Matt Harlan <mjh10@cornell#stopspammers#.edu>
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Viewed:
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2391 times
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At 6:12 AM +0000 1/16/97, Keith the wonder wookie wrote:
> At 12:27 AM 1/16/97 -0400, you wrote:
> > Keith,
> >
> > Try an LM567. It's a tone decoder with PLL and VCO. Basically set
> > the internal freq. of the 567 any where between .01 Hz up to I think 500
> > kHz. Feed a signal into the 567 and if the freq's match up, the 567's
> > output goes low. I've been messing around with using the 567's internal
> > occilator to modulate the 40 khz carrier from a 555. tring to make a
> > single unit with simply two power connections and an output.
> >
> > hope it helps
> >
> > matt
>
>
> I once tried using the internal freq of the 567 to drive the IR led. I
> figured that this would be the exact freq that the 567 was looking for and
> therfor should work. I was never able to get it to work right. If you do
> perfect this design let me know, I am very interested.
>
> Keith
Keith
I think it works. I managed to get a bread boarded version of the
IR sensor working. A 555 provides a 40khz carrier. The 555's reset pin is
directly tied to pin 5 of a 567. The carrier is modulated by the internal
freq of the 567. A sharp IR detector is sent to the 567 through a single
transistor amp stage. It works from about 12" to 15" at various angles
from straight on to about 45°. The 555 drives the IR led directly. The
LED needs to be very directional, I put a pen cap over the LED to test it.
Works pretty good. Almost 18" with a white envelope. almost 12" with my
hand. I figure you could use one Sharp module and at least 5 LED's at
equal angles around the sensor. One 555 for the carrier, and 5 different
567 all tied to the same module. Use an analog switch the cycle through
the different modulation frequencies. Maybe a '138 would do the job. Then
you could get eight different angles.
I'll keep you posted as I work on it.
matt
_______________________
Matthew J. Harlan
Cornell University
Electrical Engineering
mjh10@cornell.edu
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