I am working on a project that involves communicating with LEDs. I need to be able to detect the state of a light source that is flashing at about 100 Hz. I am using the phototransistor that comes with the Arduino Starter Kit, but I am noticing that, while the phototransistor detects a difference between the high state and low state, this is very minimal (and about 200 values higher than the phototransistor's value when the LED is completely off). I find this very confusing because the datasheet for the phototransistor claims that the reaction time is 2 microseconds, while my project is working on the scale of milliseconds.
What could be causing this? Are there any other components (preferably inexpensive) that I can use to detect light from a source that is flashing at this frequency? It would be amazing if the light sensor could yield a value when the LED is low that is the same as if the LED was never on. Any help would be very much appreciated. Thank you!
The datasheet for the photoresistor can be found here: