Subject:
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Re: IR for bots
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Fri, 28 Mar 1997 11:56:40 GMT
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Original-From:
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Pandit Panburana <pdp@ix.#saynotospam#netcom.com>
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Viewed:
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1440 times
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Hi Richard,
I believe 50% duty cycle of on/off time is just
an arbitary number which is easy to implement.
You can change to any other number or even
can be some sort of coding at the rate that
is less than center freq. or carrier (38Khz here).
Practically, it really depends on what are you trying
to do with the IR system. In the case that it is
used for short range obstrucle detection, I believe
you do not need to modulate any information
and it should be sufficient. But if you want to
make sure that the system is immune to noise from
,for example, home's TV/VCR IR type remote controls
stuff then put some coding out and make sure you see
what you sent out would help filter out these unwanted
interferences (avoid false detections).
Regards,
-Pandit
----------
> From: Richard Vannoy <richardv@abac.com>
> To: King, Terry <terry.king@fmr.com>
> Cc: handyboard@media.mit.edu
> Subject: Re: IR for bots
> Date: Thursday, March 27, 1997 11:19 PM
>
> > Or is it necessary to inject another frequency on the 40 Khz that can • be
> > decoded? Then the output of the decoder (like a 567) is read by the HB.
> > I understand that tone encoding allows for multiple tasks on one
> > carrier, But my main interest here is for object avoidance.
>
> Our robot worked well with a dual 555 timer. 38KHz for the IR and
> combined with a 500 Hz square wave. When the square wave was high, 38K
> was on, making it a 50% duty cycle transmission. As I understand the
> receiver circuitry, it was tuned to 38K. Worked fine for us, but I
> don't know the correct answers to why 50%? Why modulate? Why not just
> straight 38K?
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