March 15, 2014 at 10:24 am #11306
You can instead connect a button switch tied to +5V to simulate the liquid drip. each time u press the button, it would be like a drop passing through the sensor arrangement.
But note that it is only for simulation purpose and it can only theoretically check if your program is working. For getting the actual output, it is better to use real hardware components like Mr. Ajish said.