I've only had my aurdino duemilanove for a couple days and Im wondering if its possible to use a (Sharp IS471FE IR light detector with built-in signal processing sircuit for light modulation
Circuit) to build a decently affective speedometer. Problem is despite reading a couple of tutorials online, I have no idea how I would translate the ir detector readings for use as a speedometer. I have only a code that tells me when an object is being detected or not but the ir detector, and some speedometer code I got here but that was for a switch sensor. Any help would be appreciated. Thanks.
When this sensor detects IR, the Vo pin goes HIGH. No IR, the pin goes LOW.
Perfect. Connect the Vo pin to an analog pin. Read the analog pin in the loop method. Every time the pin goes high, whatever was blocking the light quit blocking it. Note the time and count (or not) a pulse. The next time the pin goes high, the difference between the current time and the previous time is a function of how fast the wheel is turning.
The ability of this sensor to accurately reflect the speed that the wheel is turning is related to your ability to project IR data through the wheel onto the sensor, and your ability to block the sensor periodically.
If you have wide spokes and a narrow wheel, it should not be a problem. If you have narrow spokes, and/or a wide wheel, it could be a problem.
It's why hall effect sensors are the normal way of measuring wheel speed.