My current robotics project requires me to design and build an accurate
and stable IR proximity detection sensor system. It should give feedback
of objects up to 5 feet. My chosen tools are the PIC16F84, the
LTC1298 12-bit ADC, and the VTR24F1 optosensor from EG&G.
The sensor simply contains an IR LED and a photodarlington in a single
package.

My current solution involves simple noise filtering through code. The
opto proximity method is through the use of intensity or signal
strength,
reflected off an object.

Algorithm:
        Pulse HIGH!     ; LED ON.
        Read ADC        ; Result A = Signal + Noise

        Pulse LOW!      ; LED OFF.
        Read ADC        ; Result B = Noise

        SUB A-B ; Result C = (Signal+Noise) - (Noise)

        C = pure signal strength.

This has proven to work well for distances up to 8 inches using an 8-bit
ADC. This is the first time I'm trying to extend the range, with a more
sensitive sensor and a 12-bit ADC.

Is there a better algorithm of filtering which would provide greater
results? A better sensor, or maybe a better method to the entire
project. I have played with Sharps' GP2D02 module as well; and have
gotten rather unsatisfactory results. If the current method cannot be
improved upon, then my next step is to try one of those 40 khz
Sharp IR modules. They won't give me proximity ranging, but
maybe reliable object detection; and atleast that's a start.


Sebastian