You’ve probably seen a Newton’s cradle device residing on someone’s desk. These toys — or conservation of momentum instruments, for those who like to seem more intelligent— let the user pull cord-suspended ball back then let it go. The opposite ball then bounces out on the other side, and back and forth over and over until friction brings things to a halt. As entertaining as they are, “TecnoProfesor” apparently dared to wonder how much cooler this unit would be if lit up by RGB LEDs embedded inside the spheres.
His take on the device uses not metal spheres, but ping pong balls as the objects that swing with (non-programmable) RGB LEDs embedded inside. Instead of mass transfer pushing the balls, the device is assisted by a pair of servos that simulate the traditional Newton’s cradle action, swinging the outer spheres in and out in an alternating pattern, or mirroring the swinging actions at the same time. LEDs pulse in sequence through the outer and inner orbs, for a kind of mass wave to mesmerize onlookers.
Control of the device is via an Arduino Mega, while a potentiometer is employed to adjust frequency, where a button switches between the alternating and mirrored run modes. Code and circuit diagrams are available for download in the project’s write-up.