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Reflective photoelectric sensor design issues

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Murugesh_89

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Hi,
I am designing photoelectric electric sensor of reflective type. I am detecting the objects of various colors.

When i place some objects of light colors like sky blue,grey... the detection is working. But when i place dark objects like red,black,green... the sensing is not happening for even a distance of about 10mm. I think these dark objects absorbs the light source and not reflect it back.

I am using a IR photo emitter with wavelength of 950nm by passing a current of 135mA (forward current of 150mA has given in datasheet).

What should i do to overcome this issue to detect dark color objects too..

Thanks,
Murugesh
 

First of all make sure your light emitter is actually emitting light at these wavelengths, if not use a wideband source (light bulb!!). If the objects are not reflecting any light, you tell me how you are going to detect it!
Frank
 

Thanks for your reply.

Light color objects are reflecting the light. Dark color objects only not reflecting.
So what wavelength should i use to detect both light and dark color object.
 

"o detect both light and dark color object." The lightness or darkness of a colour is its luminance. The wavelength of the reflected light is its colour. You can have a piece of black velvet with a spot of red on it, it reflects very little light but what light it reflects will be red. if you shine a green light onto the cloth it will not reflect anything at all. if you shine a red light on it it will reflect a little red light.
Frank
 

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