Subject:
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Re[4]: IR Collision avoidance
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Tue, 4 Mar 1997 09:00:04 GMT
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Original-From:
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Richard Whitehead <richard.whitehead@ukos.varian.#IHateSpam#com>
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Viewed:
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1670 times
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Adam,
I don't use -5v, I just use a single 5v supply. You have to choose
your op-amp carefully - I am currently trying ICL7612 but I'm looking
at another sort which might turn out to be better. With a single
supply, you have to bias things around 2.5v using a voltage divider
network.
I am detecting the received IR using a demodulator (precision diode)
circuit, which costs just about $2 to build. It gives an analogue
output indicating the strength of the received signal. Hence there is
no software involvement, except to poll the analogue port value.
I am considering locking the receiver to the detector to make a
synchronous demodulator, which might work better.
One advantage of my approach is that you can test it using *visible*
light if you want; because of the modulation, an ordinary red LED and
visible-light phototransistor work fine, but with much less range than
the IR reflectance sensor parts.
I will post something specific on here once it is all completely
finalised.
Richard
______________________________ Reply Separator
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Subject: Re: Re[2]: IR Collision avoidance
Author: Adam <adam@ring.zenox.com> at Internet-Mail
Date: 03/03/97 14:09
Richard,
I've tried the op-amp method and had some success. I just don't
know how I would power the -5V via the HB. Do you have any
suggestions? Thanks.
On Mon, 3 Mar 1997, Richard Whitehead wrote:
>
> Bill,
>
> Why is everyone using a digital device to try to detect the (analogue)
> distance to an object? Especially one with AGC, it makes no sense!
>
> I modulated the IR at 10KHz (high enough to be away from mains light
> flicker, but out of the way of the remote control band), and am using
> an analogue op-amp demodulator circuit to detect the strength of the
> reflected signal.
>
> It is basically working, but I am just changing to a different op-amp
> to get rail-to-rail operation.
>
> Richard
>
>
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Message has 2 Replies:
 | | Re: Re[4]: IR Collision avoidance
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| Richard, Thank you for your response. I must admit that my electronics knowledge is limited to basic theory and some practice. I depend on others, such as yourself, who have had more experience. Furthermore, I would greatly appreciate any thoughts (...) (28 years ago, 5-Mar-97, to lugnet.robotics.handyboard)
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