Weaponizing Elementary Science Experiments

November 22, 2016 by Gerrit Coetzee 31 Comments

[austiwawa] was playing around with one of those simple linear motors people build as friendly little science experiments. There’s an AA battery in the middle of a set of magnets. When you put it inside of a spring it zips around inside until you run out of spring or magic pixies in the battery.

Of course, the natural question arose, “How do I make it go fast!? Like fast!” After making explosion and woosh noises for a bit (like any good hacker would) he settled down and asked a more specific question. If I made the coil the barrel of an air gun, and then shot the battery out… would it go faster?

So, he built an air cannon. It took some ingenuity and duct tape, but he managed to line the barrel with a copper coil. After that he built an experimental set-up, because making something dangerous is only okay if it’s science. That’s the difference between sensible adults and children.

He shot three “dead” rounds through the cannon, and got a baseline result. These dead rounds were made so by placing the magnets at the improper polarity to forego the motion-boosting properties. Then he shot three live ones through. It went measurably faster! Neat!

What’s the silliest thing you’ve ever seen properly characterized? Let us know in the comments below.

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3D Printed Door Latch Has One Moving Part – Itself!

September 14, 2016 by Donald Papp 31 Comments

A group at the Hasso-Plattner Institute in Germany explored a curious idea: using 3D printed material not just as a material – but as a machine in itself. What does this mean? The clearest example is the one-piece door handle and latch, 3D printed on an Ultimaker 2 with pink Ninjaflex. It is fully functional but has no moving parts (besides itself) and has no assemblies. In other words, the material itself is also the mechanism.

The video (embedded below) showcases some similar concept pieces: door hinges, a pair of pliers, a pair of walker legs, and a pantograph round out the bunch. Clearly the objects aren’t designed with durability or practicality in mind – the “pliers” in particular seem a little absurd – but they do demonstrate different takes on the idea of using a one-piece item’s material properties as a functional machine in itself.

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Diodes With Hats: Zener And Schottky

September 12, 2016 by Gerrit Coetzee 14 Comments

For beginners, diode types can sometimes be a bit of mental gymnastics. If all it does is act like a magic pixie check valve, why are there so many kinds? Schottky diodes are typically hard to mentally set apart from the standard when described by a data sheet. Zener diodes can be downright baffling for beginners, especially when mistakenly thrown in a circuit in place of a regular 1N4001. [Afrotechmods] put together a great video explaining their difference and use cases.

In both videos he does an excellent job of describing the pros and cons while setting up experiments to exhibit each. For the Schottky it’s the faster switching and lower voltage drop. For Zener it’s less about the cons and more about exploiting its strange configuration for voltage clamps, regulators, and making expensive guitars sound bad with audio distortion circuits.

He finishes both videos with good design tips for selecting and using the parts as a burgeoning circuit designer. Diode data sheets should be less of a mystery afterwards.

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Stop Buying Expensive Circular Saw Blades, Use Paper Instead

August 28, 2016 by Gerrit Coetzee 54 Comments

[John Heisz] was contemplating the secrets of the universe when an errant thought led him to wonder, could I use a sheet of paper as the blade in my table saw?

He takes a sheet of regular printer paper, draws a circle on it the same diameter as his regular blades, and cuts it out. He then bolts it into place on the spindle, slots in the table saw insert for really really thin kerf blades, and fires it up.

The blade is surprisingly dangerous. One would maybe expect a paper blade to be minimally damaging to a finger at best, but it quickly shows itself to be capable of tearing through paper and cutting through wood at a reasonable clip. Since the paper is minimally conductive, a SawStop couldn’t save someone from a lack of caution.

The blade finally meets its match half way through a half-inch thick piece of wood scrap. Wood and paper dust explode outward as the experiment ends. Video after the break.

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Google Unveils Their Experimental Plan For Wireless Broadband Service

August 15, 2016 by Brian Benchoff 19 Comments

Two years ago, the FCC, with interested parties in Microsoft, Google, and many startups, created the Citizens Band Radio Service (CBRS), a rule that would open up the 3550-3650 MHz band to anyone, or any company, to create their own wireless backbone between WiFi access points. It is the wireless solution to the last-mile problem, and last year the FCC enthusiastically endorsed the creation of the CBRS.

In a recently released FCC filing, Google has announced their experimental protocol for testing the new CBRS. This isn’t fast Internet to a lamp pole on the corner of the street yet, but it lays the groundwork for how the CBRS will function, and how well it will perform.

Google will be testing the propagation and interference of transmissions in the 3.5 GHz band in places around the US. Most of the Bay Area will be covered in the tests, as well as Boulder, CO, Kansas City, Omaha, Raleigh, NC, Provo, UT, and Reston, VA. Tests will consist of a simple CW tone broadcast in the 3.5 GHz band.

The 3.5 GHz band is already allocated to shipborne navigation and military radar systems, posing an obvious problem to any wireless broadband system using this spectrum. To this end, the FCC is proposing a novel solution to the problem of coexistence between the CBRS and the military. Instead of simply banning transmissions in the spectrum, FCC Chairman Wheeler proposes, “computer systems can act like spectrum traffic cops.” A computer is able to direct the wireless traffic much more effectively than a blanket ban, and will allow better utilization of limited spectrum.

Google’s FCC filing is just for testing propagation and interference, and we have yet to hear anything about how a network built on 3.5 GHz spectrum will be laid out. One thing is for certain, though: you will not have a 3.5 GHz USB networking dongle for the same reason you don’t have a Google Fiber input on your desktop.

Hand-Cranked Cyclotron

October 14, 2015 by Mike Szczys 10 Comments

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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Measuring The Lifespan Of Nixie Tubes

November 24, 2013 by Brian Benchoff 28 Comments

nixie

Nixie tubes have two things going for them: they’re awesome, and they’re out of production. If you’re building a clock – by far the most popular Nixie application, you’re probably wondering what the lifespan of these tubes are. Datasheets from the manufacturers sometimes claim a lifetime as low as 1000 hours, or a month and a half if you’re using a tube for a clock. Obviously some experimentation is in order to determine the true lifetime of these tubes.

Finding an empirical value for the lifetime of Nixies means setting up an experiment and waiting a very, very long time. Luckily, the folks over at SALTechips already have a year’s worth of data.

Their experimental setup consists of an IN-13 bargraph display driven with a constant current sink. The light given off by this Nixie goes to a precision photometer to log the visual output. Logging takes place once a week, and the experiment has been running for 57 weeks so far.

All the data from this experiment is available on the project page, along with a video stream of the time elapsed and current voltage. So far, there’s nothing to report yet, but we suppose that’s a good thing.