I was just experimenting with my new Solarbotics Servo Wheel and a QRD1114 sensor, in order to make a quadrature encoder for my servo wheel. I thought that I would share the method of my madness, so that nobody out there would need to repeat my experiments needlessly...
I chose a quadrature pattern that would mount on the inside of the wheel. Print this template out and cut a hole in the middle just large enough for your axle (if necessary). Cut out using a razor blade, and trim to fit inside the wheel. The qrd1114 will reflect nicely from white paper, but barely from the black wheel.
Next, take a look at the following schematic: QRD1114 quadrature schematic. With this schematic, you will get nice clean logic levels, tuned to give you well under 1V when the white is in front of the sensor, and tuned to give you about 4.5V when the black wheel plastic is in front of the sensor. You did get a BLACK wheel, didn't you?
Next up, since the quadrature template has slats every 10 degrees, just place the quadrature encoders some multiple of 10 degrees, plus or minus 5 degrees (that's a joke... get it?) apart. This way, you get edges 90 degrees out of phase with each other. Now you can detect the edges with your interrupt on change on your uController, and measure how fast your wheel is turning! Next episode.... the quadrature code.
Posted by Enki at November 7, 2004 11:13 PM | TrackBack