DIY : This Machine Keeps a Ping Pong Ball Bouncing Indefinitely
The best machines are machines dedicated to doing just one job really well. That’s why everyone is always so eager to buy hot dog cutters and egg cubers from QVC. Multipurpose machines lack focus, and simply don’t have the devotion it takes to do one task well. That’s why this ping pong bouncer built by Tkuhn is so good at bouncing ping pong balls.
Lets just ignore the question of why Tkuhn wanted to juggle ping pong balls in perpetuity, and instead talk about how they did it. The ping pong ball is dropped onto a small wood platform, and the natural excitability of the ball causes it to start bouncing. Normally, you’d get several good bounces before the unflinching force of gravity renders it inert. Instead of letting it succumb to gravity, Tkuhn’s machine uses steppers to move the platform and keep the ball bouncing — kind of like those toys with a paddle and a ball on a string.
In this case, however, there is no string to keep the ball from bouncing off the side and onto the floor. And that’s the real beauty of Tkuhn’s stepper juggler. Each side of the platform has a microphone, and the sound of the ping pong ball bouncing is picked up by those. An Arduino then analyzes those pings to determine where on the platform the ball hit, and adjust the next hit accordingly to direct the ball back towards the center of the platform.