Electrostatically Accelerated Ping-Pong Ball Travels the Circuit

There is a special breed of hardware hacker whose playground lies in the high voltage arena. Their bench sizzles with the ozone and plasma of Tesla coils, and perhaps it’s best not to approach it without a handy fluorescent light tube to sniff for unseen hazards. There are many amazing things that can come of these experiments, and fortunately for those of us who lack the means or courage to experiment with them there are many YouTube videos to satisfy our curiosity.

One such comes from [Plasma channel], in the form of a table-top ping-pong ball accelerator. It lacks impressive sparks  but makes up for it in scientific edification, because it uses static electricity to send a conductive-paint-coated ping-pong ball spinning round the inside of a curved glass bowl. It does this using alternate positive and negatively charged strips of aluminium tape on the inside of the bowl, each of which charges the ball as it rolls over it, then giving it a bit of repulsive force to keep it spinning. His power comes from a couple of small Wimshurst machines, but no doubt other similar generators could be used instead.

The whole is an entertaining if a little hazardous talking point, and a fun weekend build. The parts are easy enough to find that you might even have them to hand. If continued electrostatic diversion floats your boat, you might like to read our recent excursion into the subject.

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Roll Your Own Trackball Mouse

What do you do when you’re into trackball mice, but nothing out there is affordable or meets all your murine needs? You build one, of course. And if you’re like [Dangerously Explosive], who has a bunch of old optical mice squeaking around the shop, you can mix and match them to build the perfect one.

The mouse, which looks frozen mid-transformation into a rodential assassin, is a customized work of utilitarian art. Despite the excellent results, this project was not without its traps. [Dangerously] got really far into the build before discovering the USB interface chip was dead. Then he tried to sculpt a base out of Plasticine and discovered he’d bought the one kind of clay that can’t be baked. After trying his hand at making homemade salt dough, he painstakingly whittled a base from scrap pine using a drill and a hacksaw.

Every bit of this mouse is made from recycled bits, which, if you pair that with the paint job and the chosen shade of blinkenlights, makes this a green mouse on three levels. One of the two parts of this mouse that isn’t literally green, the cord, is still ecologically sound. [Dangerously] wanted a really long tail, so he scavenged a charger cable built for fruity hardware and threaded it through a hollowed-out piece of purple paracord.

We love the thumb-adjacent scroll wheel and the trackball itself, which is a ping pong ball painted black. The cool part is the guide it rolls around in. [Dangerously] spent a long time hand-whittling the perfect size hole in a particularly wide mouse palm rest. All that plastic shaving paid off, because the action is smooth as Velveeta.

[Dangerously] certainly designed this mouse to fit his preferences, and ergonomics seem a bit secondary. For a truly custom fit, try using whatever passes for Floam these days.

Arduino Laser Pinball is On Target

Have you ever wanted to roll your own pinball machine? It’s one of those kinds of builds where it’s easy to go off the deep end. But if you’re just getting your feet wet and want to mess around with different playfield configurations, start with something like [joesinstructables]’ Arduino Laser Pinball.

It’s made from meccano pieces attached with standoffs, so the targets are easy to rearrange on the playfield. [joesinstructables] wanted to use rollover switches in the targets, but found that ping pong balls are much too light to actuate them. Instead, each of the targets uses a tripwire made from a laser pointing at a photocell. When the ping pong ball enters the target, it breaks the beam. This triggers a solenoid to eject the ball and put it back into play. It also triggers an off-field solenoid to ring a standard front-desk-type bell one to three times depending on the target’s difficulty setting.

The flippers use solenoids to pull the outside ends of levers made from meccano, which causes the inside ends to push the ball up and away from the drain. Once in a while a flipper will get stuck, which you can see in the demo video after the break. An earlier version featured an LCD screen to show the score, but [joesinstructables] can’t get it to work for this version. Can you help? And do you think a bouncy ball would actuate a rollover switch?

This isn’t the first pinball machine we’ve covered. It’s not even the first one we’ve covered that’s made out of meccano. Here’s an entire Hacklet devoted to ’em. And remember when an Arduino made an old table great again?

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Hand-Cranked Cyclotron

Okay, not actually a cyclotron… but this ball cyclotron is a good model for what a cyclotron does and the concepts behind it feel kooky and magical. A pair of Ping Pong balls scream around a glass bowl thanks the repulsive forces of static electricity.

It’s no surprise that this comes from Rimstar, a source we’ve grown to equate with enthralling home lab experiments like the Ion Wind powered Star Trek Enterprise. Those following closely will know that most of [Steven Dufresne’s] experiments involve high voltage and this one is no different. The same Wimshurst Machine he used in the Tea Laser demo is brought in again for this one.

A glass bowl is used for its shape and properties as an insulator. A set of electrodes are added in the form of aluminum strips. These are given opposite charges using the Wimshurst machine. Ping Pong balls coated in conductive paint are light enough to be moved by the static fields, and a good crank gets them travelling in a very fast circuit around the bowl.

When you move a crank the thought of being connected to something with a chain pops into your mind. This feels very much the same, but there is no intuitive connection between the movement of the balls and your hand on the crank. Anyone need a prop for their Halloween party?

If you don’t want to buy or build a Wimshurst machine you can use a Van De Graaff generator. Can anyone suggest other HV sources that would work well here?

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Cannon Sucks Balls at 600 mph

Every day we humans hang out and think nothing of the air that is all around us. It is easy to forget that the air has mass and is pulled down to the earth by gravity creating an ambient pressure of about 14.7 psi. This ambient pressure is the force that crushes a plastic bottle when you lower the internal pressure by sucking out the air. [Prof Stokes] from Brigham Young University has used this powerful ambient air pressure as the power source of his ping pong ball cannon.

Instead of filling a reservoir tank with compressed air and using that to fire a projectile, this canon has the air removed from the barrel to create the pressure differential that propels the ping pong ball. The ball is put in one end of a 10 ft long tube. That end of the tube is then covered by a sheet of Mylar. The other end is covered with the bottom of a disposable plastic cup. A vacuum pump is then used to remove the air inside the tube and it is this pressure differential that keeps the plastic cup secured to the end of the tube. When it’s firing time, a knife is used to cut the Mylar at the ping-pong-ball-end of the tube. Air rushes in to fill the vacuum and in doing so accelerates the ping pong ball towards the other end. There is a large jar at the business-end of the cannon that catches the ping pong ball and contains the shrapnel created during the ball’s rapid deceleration!

Since this was a science experiment at a university, some math was in order. Based on the atmospheric pressure and ball cross sectional area, the calculated speed was 570 meters/second or about 1300 mph. The calculations didn’t take into account leakage between the ball and the tube or viscosity of the air so a couple of lasers were set up at the end of the cannon to measure the actual speed – 600 mph. Not too bad for just sucking the air out of a tube!

The Old Ping-Pong Ball Levitation Trick

pingpongLev

[Jacob] has put a slightly new twist on the levitating ball trick with his ping-pong ball levitation machine. We’ve all seen magnetic levitation systems before. Here on Hackaday, [Caleb] built a Portal gun which levitated a Companion Cube. Rather than go the magnetic route, [Jacob] levitated a ping-pong ball on a cushion of air.

Now, it would be possible to cheat here, anyone who’s seen a demonstration of Bernoulli’s principle knows that the ball will remain stable in a stream of air. [Jacob] proves that his system is actually working by levitating ping-pong balls with different weights.

A Parallax Ping style ultrasonic sensor measures the distance between the top of the rig and the levitating ball. If the ball gets above a set distance, [Jacob’s] chipKit based processor throttles down his fans. If the ball gets too low, the fans are throttled up. A software based Proportional Integral Derivative (PID) loop keeps the system under control. A graph of the ball distance vs fan speed is displayed on an Android tablet connected to the controller via USB.

When [Jacob] switches a heavy ball for a light one, the lighter ball is pushed beyond the pre-programmed height. The controller responds by reducing the fan speed and the ball falls back. Who said you can’t do anything good with a box of corn dogs?

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CNC ping pong printer uses simple construction

spherebot

This is one of the simplest CNC builds we’ve seen but it still functions quite well. It’s a clone of the EggBot, but is aimed at printing on spherical Ping Pong balls rather than oblong eggs. [Chad] calls it the Spherebot, but you should be careful not to confuse it with the morphing sphere robot which can walk around like a hexapod.

The project is both mechanically and electronically simple. The body of the printer is made up of three acrylic plates, which we’re sure were clamped together when drilling holes to guarantee proper alignment. Threaded rod and nuts are used to mount the plates to one another, as well as to hold the sphere in place while printing. One stepper motor turns the ball while the other pivots the pen mount. A servo motor is responsible for lifting the pen. The entire thing is driven by an Arduino along with two stepper motor driver boards. Don’t miss [Chad’s] presentation embedded after the break.

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