I worked with a team to build a simple circuit to power 2 lines of infrared emitters (one line on the top of the square frame and one line on the bottom of the square frame). I connected another simple power and feedback circuit to two lines of infrared phototransistors (that were lined up opposite the emitters). The emitters were connected to the back of the frame and positioned to emit light through small holes (in order to minimize the infrared beam spread width). The detectors sent a logic high or logic low signal back to the Arduino to let me know whether or not the infrared phototransistor was receiving infrared light. If no phototransistors were being blocked, they would produce logic lows and my code would print out a square grid of all 0s. If the ball crossed several phototransistors and blocked the light, then my code would find the average of the positions of the phototransistors that sent high signals and it would print out a 1 in the location where the ball crossed. I’m currently trying to implement shift registers to allow more phototransistors to be hooked up to the Arduino. I attached a picture of the simple circuit I used to attach the phototransistors