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inetquestion
electronics forum beginner
Joined: 04 Mar 2006
Posts: 4
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 Posted: Sun Jun 25, 2006 3:56 pm Post subject:
infrared proximity sensor
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I've been working on an ir proximity sensor, but am having problems
with its sensitivty. With the emitter and detector side by side, the
approaching object has to be about 3 inches away before any objects are
detected. Is there a way to get more sensitivity out of these systems?
One other question I have is about the emitter circuit. Right now the
best output i've found is any tv remote. The ones i've build tend to
burn out the emitter or are way to weak. Is there something really
simple I'm missing?
Regards,
-Inet |
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Jamie
electronics forum Guru
Joined: 24 Mar 2005
Posts: 597
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| Posted: Sun Jun 25, 2006 4:24 pm Post subject:
Re: infrared proximity sensor
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inetquestion wrote:
| Quote: | I've been working on an ir proximity sensor, but am having problems
with its sensitivty. With the emitter and detector side by side, the
approaching object has to be about 3 inches away before any objects are
detected. Is there a way to get more sensitivity out of these systems?
One other question I have is about the emitter circuit. Right now the
best output i've found is any tv remote. The ones i've build tend to
burn out the emitter or are way to weak. Is there something really
simple I'm missing?
Regards,
-Inet
maybe its the way your Tx and Rx it ? |
if your looking for a simple presents of
IR in the Rx LED then you might have problems
there since the levels will vary alot..
using mulitple Tx leds also helps to spread
the radiation patern around a bit.
you should be using a pulsed IR tx output and
on the RX end passing it through a bandpass filter
to clean up other noise.
if you use op-amp with the - input for the RX
LED and then have a resistor from that input over to the
+ input with a series LC reasonator from the + input to
common selected for the carrier frequency your using, you
should be able to detect very weak to strong signals with no problem.
i did such a project years ago.
you can simply use a cap to common if you wish for only
the high freq effects to the present but then you may
run into problems of other IR devices tripping the signal
unless you use a PLL chip like the old LM567 i think it was?
--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5 |
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Luhan
electronics forum Guru
Joined: 10 Dec 2005
Posts: 365
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| Posted: Sun Jun 25, 2006 4:26 pm Post subject:
Re: infrared proximity sensor
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inetquestion wrote:
| Quote: | I've been working on an ir proximity sensor, but am having problems
with its sensitivty. With the emitter and detector side by side, the
approaching object has to be about 3 inches away before any objects are
detected. Is there a way to get more sensitivity out of these systems?
One other question I have is about the emitter circuit. Right now the
best output i've found is any tv remote. The ones i've build tend to
burn out the emitter or are way to weak. Is there something really
simple I'm missing?
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How about the wavelength of your emitter - does it match the detector?
How about the frequency of the modulation - does that match the
detector?
I'm assuming the emitter is normally off, and only pulses on for the
modulation with a near 50% duty cycle.
Luhan |
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