Subject:
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Re: ir obstacle detector
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Tue, 10 Dec 1996 04:31:50 GMT
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Original-From:
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Fred G. Martin <fredm@!nospam!media.mit.edu>
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Viewed:
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1638 times
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In your message you said:
> > Included in the fax they send you is a schematic for a transmitter and
> > receiver. I used the transmitter and then, since I wasn't interested in
> > decoding the signal, I used the output as it was, with a capacitor to do
> > a bit of smoothing. Connected it to the Handy/Mini board analog sensor
> > inputs and it gives a distinct level change as an object gets to within
> > about 20 cm.
>
> Why is the distance do short?
> You can use a remote control for a TV or someting from really far away and ev
en bounce the IR off walls.
yes, but the tv remote technology includes automatic gain circuits, so
you have no way of telling HOW FAR AWAY the original signal source is.
> Doesn't that mean that you can do the same for a sensor?
> Or is it that the current generation of phototransistors are not sensitive en
ough?
You can use a simple reflectance sensor, as illustrated in the HB Tech
Ref, to get readings between 1" and zero. Beyond 1" there isn't
enough reflection.
More complicated circuits (e.g., modulation) let you do a better job
of factoring out ambient light and get readings out to a foot or so.
Beyond that is hard, unless you do something a lot more fancy (e.g.,
lasers).
-Fred
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Message is in Reply To:
 | | Re: ir obstacle detector
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| (...) Why is the distance do short? You can use a remote control for a TV or someting from really far away and even bounce the IR off walls. Doesn't that mean that you can do the same for a sensor? Or is it that the current generation of (...) (28 years ago, 10-Dec-96, to lugnet.robotics.handyboard)
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