An LDR like he is using has a typical response time of up to 18ms. Better to use a phototransistor which will respond in the order of μs. [1] is $0.95. http://

An LDR like he is using has a typical response time of up to 18ms. Better to use a phototransistor which will respond in the order of μs. [1] is $0.95. http://lednique.com/opto-isolators-2/light-dependent-resistor-ldr/ http://lednique.com/opto-isolators-2/light-dependent-resisto... https://www.adafruit.com/product/2831 https://www.adafruit.com/product/2831