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'[OT]: IR sensors'
2000\12\15@215355 by Henry Low

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Is the range for IR sensors adjustable?? If yes, by how much?? Can anyone
share their experience with the use of IR sensors on robots?? Extra
circuitry are also required probably and any willing to share??

Henry

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2000\12\15@235739 by Roman Black

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Henry Low wrote:
>
> Is the range for IR sensors adjustable?? If yes, by how much?? Can anyone
> share their experience with the use of IR sensors on robots?? Extra
> circuitry are also required probably and any willing to share??
>
> Henry


I use pigsnouts (trans/receive pair) and interruptors
all the time. I usually have quantities of them lying around
stripped from VCRs, and when I find one I like for a
project I can then order them from my TV spares supplier
in quantity.

I assume you are talking about pigsnouts as you want
to reflect off a surface for proximinty detection?

In VCRs they use a simple DC driven system, the led
is activated with a few mA, and the receiver diode
is grounded at one side and tied to 5v by about a 4.7k
resistor. (reverse connected!) This generally gives
a pretty fair logic level output, if no reflective
surface or black, diode is high resistance and is logic
1. If reflective white (etc) that is close enough, the
voltage drops low enough to cause a logic 0. They use
this simple circuit on the reflective encoders in VCRs,
just black plastic disk with small silver foil pieces.
These encoders are often under the spools.

I have used similar circuits to use these as proximity
detectors. By increasing the led current up to about
20mA, and changing receiver resistor value, you can get
logic level triggering on proximity from your hand
(palm) at about 4 inches, your fingertip at one inch.
White paper gives about twice the range of skin,
and black surfaces can be close to non-detectable.

These pigsnouts are best suited as "table" sensors
mounted a few mm above the table, at the corners of
your bot. They will detect the edge of the table and
stop bot falling off with pretty good reliability.

So for one 4-wire pigsnout and 2 resistors you can
have proximity sensing into one PIC pin. This can
give perfect results for table sensing/sumo and even
wall proximity sensing with micromouse in a white-walled
maze. It can also be anywhere from great to useless
in real world proximity sensing depending what color
the surfaces are. I measured 10:1 difference between
white paper signal and many dark objects. Black plastic
as used in appliances and remote controls is almost
invisible.

You can use ac modulated led and an ac amp on the
receiver to give a huge increase in gain, but by the
time you can sense black at 4 inches you will sense white
wall 10 feet away! I've tried it! Proper "ranging"
proximity sensing requires a very different approach.
:o)
-Roman

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2000\12\17@143618 by Dan Michaels

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Complete IR ranging solution:

http://www.acroname.com/robotics/parts/R19-IR02.html

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2000\12\18@060922 by jcsa Laszlo AII III

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check this page
http://www.xs4all.nl/~sbolt/e-index.html

it's a nice IR radar, which i try it and it works well








                                              Kajcsa Laszlo

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2000\12\18@074002 by Roman Black

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Dan Michaels wrote:
>
> Complete IR ranging solution:
>
> http://www.acroname.com/robotics/parts/R19-IR02.html

Thanks Dan, that's the one I was talking about. But
I remember something about them being $12 US not
$21??
-Roman

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