Query on Infra Red sensor

Hi all

I have a qn on IR sensors.

My IR sensor (juz the device connected to controller with resistors) is activated (thru digital or analog ports) regardless of whatever object is placed over it, black or white. I need it to be activated by a reflective white surface onli, and not juz any black surface.

The sensor shows a slight difference in volt reading/ analog output reading between a white surface and a black surface. I need it to show a very large difference so that the robot can know distinctly when a black surface is passed over it, or when a white surface is passed over it.

How can i go about doing this?

Thank you for advising

put an transitor in to amplefy it

lil'gal said:

The sensor shows a slight difference in volt reading/ analog output reading between a white surface and a black surface. I need it to show a very large difference so that the robot can know distinctly when a black surface is passed over it, or when a white surface is passed over it.

Click to expand...

Have you got a direct shine path between emmiter and detector?

regards,
colin

You can try using a comparitor to read the reflection strenght to see if it passes a certain "threshold level." The comparitor would have two input voltages: (1) a reference voltage, and (2) your input signal from the IR transmitter. The comparitor will check to see which input is higher and give you a + or - output based on the comparison. If your output is still constantly on, just keep adjusting the reference voltage until it can differentiate between light and dark.

LM339 seems to be a pretty standard model and you can still get them at most Radio Shacks if you are in the U.S. **broken link removed** shows something similar to what you described.