how to count blinking LED flashes using arduino uno boards and LDR? i want to know code for counting the flashes of LEDs and display no. of flashes in particular time given.by using LDR.
basically i tried it with interrupts but i'm not getting it,so please help in this regard.
LDRs only give an analog output, proportional to the amount of light. 

To make it give a HIGH and LOW value, you have to tweak the other resistor used in the voltage divider. 

Alternatively you could use analogRead and add a threshold value in your code.