Query on Infra Red sensor - Electronic Circuits Projects Diagrams Free

lil'gal · 2nd February 2005, 11:02 AM

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

Someone Electro · 2nd February 2005, 07:12 PM

put an transitor in to amplefy it

slurp · 3rd February 2005, 07:47 PM

Quote:

Originally Posted by lil'gal

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.

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

regards,
colin

DigiTan · 4th February 2005, 03:33 AM

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. This page shows something similar to what you described.

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2nd February 2005, 11:02 AM	(permalink)
lil'gal	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

2nd February 2005, 07:12 PM	(permalink)
Someone Electro	put an transitor in to amplefy it __________________ Il give you shocking experience.

4th February 2005, 03:33 AM	(permalink)
DigiTan	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. This page shows something similar to what you described. __________________ The most-hated young engineer in America. * AVR Projects * Robot War: TI * About