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In a simple ir module using ir transmiitter and ir receiver to detect an obstacle , why black bodies are not detected ? Answered

i have observed that black objects are not detected as ir rays are absorbed by the black object also the cicuit does not work when sunlight falls on it?how can i solve this problem?? please help ?

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mpilchfamily (author)2012-10-11

Don't use IR. As you have found out there are problems that can't be overcome. You can't do anything about black objects not being seen but you can ad an IR filter to the receiver to help filer out all but the IR frequency of your transmitter. But even then you'll still get noise from sun light.

What you need is a sonic range finder for obstacle detection.

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bwrussell (author)mpilchfamily2012-10-11

+3, black objects are absorbing most light, not just visible light. The sun is flooding the sensor with IR light which masks the signal from your transmitter. Ultrasonic transducers are cheap and should easily interface with most microcontrollers.

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sandiri (author)bwrussell2012-10-11

could you tell me how an ultrasonic transducer work for my requirement

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bwrussell (author)sandiri2012-10-11

It sends out ultrasonic sound waves and times how long it takes to hear them bounce back.
THESE ones are $2 right now, buy a few and experiment. I have one but haven't got around to testing it.

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sandiri (author)bwrussell2012-10-17

thanks a lot sir for giving a valuable idea

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quatch (author)sandiri2012-10-11

random ultrasonic sensor: https://www.sparkfun.com/products/639

I've got one coming from china via ebay for $4. Won't be near as accurate, but your intended use can guide that decision.

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mpilchfamily (author)sandiri2012-10-11

It does the same thing as the IR setup but uses ultrasonic sounds rather then IR light. Of course the actual numbers feeding into the micro controller will be different.

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quatch (author)mpilchfamily2012-10-11

Unless it is a very nice matte black body you might be able to get something back from it. Try higher power with a modulated IR (like https://www.adafruit.com/products/157 ) setup to eliminate the solar contribution?

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