Re: How to design an infra-red circuit to detect small obstacle (e.g. finger) ?
From: Larry Brasfield (donotspam_larry_brasfield_at_hotmail.com)
Date: 02/13/05
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Date: Sun, 13 Feb 2005 13:34:22 -0800
"anwar" <anwar09@yahoo.com> wrote in message
news:1108322577.860629.36920@c13g2000cwb.googlegroups.com...
> Hi,
Hi.
> I am trying to figure out how to design a simple infra-red circuit
> so that it can detect any small obstacle placed/passed in between
> infra-red receiver/transmitter. I want a light to turn on or whatever
> else to happen when this obstacle is detected.
It would help if you stated what optical setup you
have in mind. Would it be enough to detect that
a narrow beam has been interrupted?
> The distance between receiver/transmitter will be maximum 2 feet and
> minimum 6 inch.
A simple way to make a fairly sensitive transceiver
and detector is to use a NE567 tone decoder.
Depending on the gain you need, an additional
op-amp stage might be needed or you can use
a phototransistor as a gain element with suitable
external components.
This virtues of this technique are low parts count and
relative insensitivity to DC or line frequency light.
If this interests you, say so and I'll provide such
details as are not obvious.
-- --Larry Brasfield email: donotspam_larry_brasfield@hotmail.com Above views may belong only to me.
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