My final project was a waterfall using blue LED’s. The lights respond to a ping sensor in the front. When the sensor has something in front of it the lights will turn off and stay off until the object is moved. The sensor is set to change the lights when something is less than 46cm from it. That way the bottom of the piece or the floor won’t turn off the LEDs. The arduino was used to do that programming. The LED’s are individually connected to a resister on the negative leg. All of the resistors (the negative of the LED) are connected and then wired to one ground pin. The positive side of the LED’s are individually wired to separate digital output pins on the arduino (numbers 11 – 2). The code I used controlled what the sensor was doing after it measured a distance. A 9v battery powers the arduino, LED’s and sensor.