To download code and more info: http://mechatronicstutorials.blogspot.com/2014/07/balancing-of-ball-on-beam-using-arduino.html
I used Arduino as a PID controller to balance a small ball on a 4-bar mechanism. An ultrasonic sensor detects the position of the ball. A PID code is used to compute the angle of the servo motor based on the position of the ball. I used Matlab to plot the position of the ball vs time.
Parts used: - Arduino Uno - Ping))) ultrasonic sensor - 20 Kg.cm Digital Servo Motor - 5 V DC power supply