QTR-1RC Reflectance Sensor
... to take an analog reading of reflected IR by measuring the discharge time
of the capacitor. Shorter capacitor discharge time
is an indication of greater reflection.
The LED current-limiting resistor is ... strong reflectance, the discharge time
can be as low as several dozen microseconds; with no reflectance, the discharge time
can be up to a few milliseconds. The exact time
of the discharge depends on ...