[...] i thought i would be able to use it for edge detection. is this possible ??
Possible yes, but a little tedious to work with IMO.
if soo can somebody give me some sample code. im using a arduino.
First off, their description on how it is used with the schematic on the page is wrong.
Interfacing the QTR-1RC Output to a Digital I/O Line
Like the Parallax QTI, the QTR-1RC module has sensor outputs that require a digital I/O line capable of first charging the output capacitor (by driving the line high) and then measuring the time for the capacitor to discharge through the phototransistor. This measurement approach has several advantages, especially when multiple units are used:
It's the exact contrary.
You set the I/O port to output and set it high to discharge the capacitor and then set it to input and measure the time taken until the port reads low, by charging the capacitor through the phototransistor (with a current that will depend on amount of incoming light and hence the speed).