IR compensation

[qtommer]

IR sensors as we know reflect better of white surfaces compared to black.

Whilst testing my IRs, i noticed that for a distance of 1 inch away on a black surface, the voltage output is approximately 2.5V. However, a white surface material would have to be located at least 5 inches away for a voltage output of 2.5V..

This is not feasible for me as I am feeding my sensor outputs to comparators which in turn go to a PIC. If my system requires detecting both black and white..
Is there any way to compensate between the two whilst reducing the vast distance difference?

thanks!=)

 

[crutschow]

Questions, questions--

What is the voltage when nothing is detected?
Is there a specific distance you want to detect, and not detect outside that range?
Is there something that gets into the field that you do not want to detect?

Otherwise I would just set the threshold for the black surface. I don't know of any way to compensate for the different reflectivities other than that.

 

[qtommer]

Otherwise I would just set the threshold for the black surface. I don't know of any way to compensate for the different reflectivities other than that.

yes sir that's exactly what i taught of doing.
but then im actually detecting a model of a parking lot for my self parking RC car and the wall distances are fixed. Hence, if i set the threshold for black, which is at 2.5V to detect the front wall which is 1 inch away, when a white wall is placed instead, the wall would have to be at least 5 inches away which "eliminates" the tight parking space parking that my car is doing...hmmm..i guess id just have to make do with a white parking lot..
thanks anyway=)

 

[crutschow]

The other way would be to use an ultrasonic ranger which would be insensitive to color.

 

[Mr RB]

Or a Sharp IR distance sensor that people use in robotics;
Sharp IR distance sensor project (at page bottom)