Hi, im Thavamaran and currently in final year of my degree, so im using TCS230, its a CMOS color sensor whereby im doing various types of test. TCS230 output is frequency and its digital. so i was doing a test recently whereby i place my sensor about +-5cm from a surface, which the surface consists of a particular color paper.

So from 5cm when i slowly decrease to 4 cm ,3 cm and so on till i stick my sensor to the paper, the output frequency was slowly decreasing when the distance decrease. and when i increase my distance from 5cm, like say 6 cm and onwards, the frequency output increase.

Can i know why its characteristic is like that? what is the relationship between light intensity and distance?

PS: the illumination for the sensor was the fluorescent light in my lab, no external illumination.

 

Per the data sheet:

The output is a square wave
(50% duty cycle) with frequency directly proportional to light intensity (irradiance)

As you move the sensor closer the lighted surface appears brighter to the sensor. Think about the "inverse square law" of radiation.

Ken

 

Too many variables with a setup like that. Go to TAOS and look through their app notes - http://www.taosinc.com/downloads.aspx.

 

Hey KMoffett, im sorry for bothering you, but i dont really know what is inverse square law of radiation, so can you explain to me in a least detailed way.

beenthere, thanks for the link, i went through it.

Thanks guys.

 

Google is always my friend and yours:
http://en.wikipedia.org/wiki/Inverse_square_law

Basically if you double the distance between the sensor and the light source (your colored paper), the intensity of the light will be reduced to 1/4th the initial intensity...1/(2x2). If you moved it three times the original distance, the sensed intensity would be only 1/9th the original intensity...1/(3x3). If you moved the sensor to only 1/2 the original distance the sensed intensity would be 4 times the original...1/(0.5x0.5).

Ken

 

Inverse square law - the intensity of all electromagnetic radiation decreases according to the square of the distance from the source. Here is the Wikipedia article - http://en.wikipedia.org/wiki/Inverse_square_law.