Robotic Ball Bouncer Uses Machine Vision To Stay On Target

When we first caught a glimpse of this ball juggling platform, we were instantly hooked by its appearance. With its machined metal linkages and clear polycarbonate platform, its got an irresistibly industrial look. But as fetching as it may appear, it’s even cooler in action.

You may recognize the name [T-Kuhn] as well as sense the roots of the “Octo-Bouncer” from his previous juggling robot. That earlier version was especially impressive because it used microphones to listen to the pings and pongs of the ball bouncing off the platform and determine its location. This version went the optical feedback route, using a camera mounted under the platform to track the ball using OpenCV on a Windows machine. The platform linkages are made from 150 pieces of CNC’d aluminum, with each arm powered by a NEMA 17 stepper with a planetary gearbox. Motion control is via a Teensy, chosen for its blazing-fast clock speed which makes for smoother acceleration and deceleration profiles. Watch it in action from multiple angles in the video below.

Hats off to [T-Kuhn] for an excellent build and a mesmerizing device to watch. Both his jugglers do an excellent job of keeping the ball under control; his robotic ball-flinger is designed to throw the ball to the same spot every time.

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Edge-Lit Ping Pong Paddle Lights Up The Fight

[George] and his coworkers like to blow off a little lunchtime steam on the company ping pong table. We might do the same, except it’d just be us versus the wall, and most of the exercise would consist of bending over to pick the ball up off the floor. When he found a scrap piece of acrylic out in their shop, [George] got the bright idea to make an edge-lit paddle featuring the company’s logo.

Not only does the paddle look cool, it works pretty well, too, even though it’s heavier and has smooth surfaces compared to a standard paddle. To begin, [George] found a regulation-size paddle outline and imported it into SolidWorks, then designed all the necessary cuts for the LEDs and other electronics. He also designed and printed ergonomic grips to protect the goods.

Continuing the stuff-on-hand theme, [George] used through-hole LEDs and dug into the abundance of battery clips and springs they have lying around for designing prototypes, instead of making it all fancy with SMT LEDs and a rechargeable battery pack. Slip on those sweatbands, because we’re serving up the build video after the break.

We see more ping pong balls than paddles around here, and that’s probably because they make great LED diffusers.

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Glitching LED Display Proves Crowd Favorite

There’s something enchanting about the soft glow of a properly diffused LED, and this is only improved by greater numbers of LEDs. [Manoj Nathwani] was well aware of this, setting out to build a large display using ping-pong balls for their desirable optical qualities.Unfortunately, not everything went to plan, but sometimes that’s not all bad.

The matrix, built back in 2016 for EMF Camp, was sized at 32×18 elements, for a total of 576 pixels. This was achieved with the use of 12 WS2811 LED strips, with the lights set out on a 50mm grid. Cheap knock-off pingpong balls were used for their low cost, and they proved to be excellent diffusers for the LEDs.

With everything wired up to a NodeMCU, basic testing showed the system to be functioning well. However, once the full matrix was assembled in the field, things started to fall over. Basic commands would work for the first 200 LEDs or so, and then the entire matrix would begin to glitch out and display random colors. Unable to fix the problem in the field, [Manoj] elected to simply run the display as-is. Despite the problems, passers-by found the random animations to be rather beautiful anyway, particularly at night.

After the event, [Manoj] determined the issue was due to the excessive length of the data line, which in the final build was 48 meters long. While the problem may be rectified when [Manoj] revisits the project, the audience seemed to appreciate the first revision anyway.

LED displays will be a hacker staple until the heat death of the universe. Ping pong balls will also likely retain their position as a favorite diffuser. If you’ve got a great LED build of your very own, be sure to hit up the tips line!

Trick Shot Bot Flings Balls Into Wine Glass Every Time

We’ve heard of beer pong, but we’re not sure we’ve heard of wine pong. And certainly never wine pong automated with a ping pong ball throwing robot like this one.

There’s not a huge amount of detail available in the video below, and no build log per se. But [Electron Dust] has a few shots in the video that explain what’s going on, as well as a brief description in a reddit thread about the device. The idea is to spin a ball up to a steady speed and release it the same way every time. The rig itself is made of wood and spun by plain brushed DC motors – [Electron Dust] explains that he chose them over PWM servos to simplify things and eliminate uncertainty in the release point. The ball is retained by a pair of arms, each controlled by a pair of hobby servos. An Arduino spins along with everything else and counts 50 revolutions before triggering the servos to retract and release the ball. A glass positioned at the landing spot captures the ball perfectly once everything is dialed in.

Here’s hoping that build details end up on his blog soon, as they did for this audio-feedback juggling machine. And while we certainly like this project, it might be cool if it could aim the ball into the glass. Or it could always reposition the target on the fly.

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Ping Pong Ball-Juggling Robot

There aren’t too many sports named for the sound that is produced during the game. Even though it’s properly referred to as “table tennis” by serious practitioners, ping pong is probably the most obvious. To that end, [Nekojiru] built a ping pong ball juggling robot that used those very acoustics to pinpoint the location of the ball in relation to the robot. Not satisfied with his efforts there, he moved onto a visual solution and built a new juggling rig that uses computer vision instead of sound to keep a ping pong ball aloft.

The main controller is a Raspberry Pi 2 with a Pi camera module attached. After some mishaps with the planned IR vision system, [Nekojiru] decided to use green light to illuminate the ball. He notes that OpenCV probably wouldn’t have worked for him because it’s not fast enough for the 90 fps that’s required to bounce the ping pong ball. After looking at the incoming data from this system, an algorithm extracts 3D information about the ball and directs the paddle to strike the ball in a particular way.

If you’ve ever wanted to get into real-time object tracking, this is a great project to look over. The control system is well polished and the robot itself looks almost professionally made. Maybe it’s possible to build something similar to test [Nekojiru]’s hypothesis that OpenCV isn’t fast enough for this. If you want to get started in that realm of object tracking, there are some great projects that make use of that piece of software as well.

Ping Pong Spectrum Analyzer

A spectrum analyzer is a pretty useful tool for working with signals where the size of the frequency components matter. Usually, the display is a screen. Sometimes, you see it done with LEDs. [Mag Laboratories] did it with ping pong balls.

The device uses a processor to calculate a Fourier transform, cutting an audio signal into 16 frequency bands. The processor converts each of these values to a PWM output that drives small fans. The fans blow the ping pong ball up the tube proportional to the fan speed. You can see the result in the video below.

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FPGAs Keep Track Of Your Ping Pong Game

It’s graduation time, and you know what that means! Another great round of senior design projects doing things that are usually pretty unique. [Bruce Land] sent in a great one from Cornell where the students have been working on a project that uses FPGAs and a few video cameras to keep score of a ping-pong game.

The system works by processing a live NTSC feed of a ping pong game. The ball is painted a particular color to aid in detection, and the FPGAs that process the video can keep track of where the net is, how many times the ball bounces, and if the ball has been hit by a player. With all of this information, the system can keep track of the score of the game, which is displayed on a monitor near the table. Now, the players are free to concentrate on their game and don’t have to worry about keeping score!

This is a pretty impressive demonstration of FPGAs and video processing that has applications beyond just ping pong. What would you use it for? It’s always interesting to see what students are working on; core concepts from these experiments tend to make their way into their professional lives later on. Maybe they’ll even take this project to the next level and build an actual real, working ping pong robot to work with their scoring system!

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