If you want something different, I don't know your cost restrictions, but
for $25.00 each and $18.00 in small qty. Siemens offers a 2.4 GHz Doppler
radar sensor, with antenna built in. (Part number KMY 24) A complete sensor
that will determine distance and direction by monitoring 2 sensor outputs
with your A/D microcontroller. Up to 15 feet possible,and very small in
size. (1.125"x1.5"x.375" approx.) I use them there are great. The Marshal
distributor in Kansas City MO. has stock.

Gordon Varney


----- Original Message -----
From: Dwornik, Sebastian <SDwornik@CRSROBOTICS.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, August 25, 1999 1:08 PM
Subject: Signal filtering through code


> 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