Author: Al Williams

4505 Articles

Drum On A Chip–Not That Kind Of Chip

November 3, 2016 by 5 Comments

Comedian Mitch Hedberg had a theory about Pringles potato chips. His theory is the company formed to make tennis balls. But instead of a truckload of rubber, someone accidentally sent them potatoes, so they made the best of it. Certainly the Pringles can is an iconic brand all by itself. The cans also have a lot of hacker history, since they are commonly used for WiFi cantennas (even though it might not be the best choice of cans). People also use them to build pinhole cameras, macro lenses, and a variety of cannon-like devices.

[Ian H] uses the short Pringles cans to build a drum kit. Clearly, the little cans aren’t going to make very much sound on their own, but with a piezo speaker element used in reverse, the cans become touch sensors that feed an Arduino and drive a MIDI device. You can see a video of the result, below.

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Minimal Arduino Clock

November 2, 2016 by 19 Comments

Making a clock with a common microcontroller like an Arduino isn’t very difficult. However, if you’ve tried it, you probably discovered that keeping track of wall time is difficult without some external hardware. [Barzok] has a very minimal clock build. It takes a handful of LED arrays with an integrated driver, an Arduino Nano, a real-time clock module, and a voltage regulator.

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Machine Learning: Foundations

November 2, 2016 by 33 Comments

When you want a person to do something, you train them. When you want a computer to do something, you program it. However, there are ways to make computers learn, at least in some situations. One technique that makes this possible is the perceptron learning algorithm. A perceptron is a computer simulation of a nerve, and there are various ways to change the perceptron’s behavior based on either example data or a method to determine how good (or bad) some outcome is.

What’s a Perceptron?

I’m no biologist, but apparently a neuron has a bunch of inputs and if the level of those inputs gets to a certain level, the neuron “fires” which means it stimulates the input of another neuron further down the line. Not all inputs are created equally: in the mathematical model of them, they have different weighting. Input A might be on a hair trigger, while it might take inputs B and C on together to wake up the neuron in question.
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Mastering Ball Screws

November 2, 2016 by 32 Comments

Most inexpensive 3D printers use a type of lead screw to move some part of the printer in the vertical direction. A motor turns a threaded rod and that causes a nut to go up or down. The printer part rides on the nut. This works well, but it is slower than other drive mechanisms (which is why you don’t often see them on the horizontal parts of a printer). Some cheap printers use common threaded rod, which is convenient, but prone to bad behavior since the rods are not always straight, the threads are subject to backlash, and the tolerances are not always the best.

More sophisticated printers use ACME threaded rod or trapezoidal threaded rods. These are made for this type of service and have thread designs that minimize things like backlash. They typically are made to more exacting standards, too. Making the nut softer than the rod (for example, brass or Delrin) is another common optimization.

However, when lead screws aren’t good enough, mechanical designers turn to ball screws. In principle, these are very similar to lead screws but instead of a nut, there is a race containing ball bearings that moves up and down the screw. The ball bearings lead to less friction.

Misumi recently posted a few blog articles about ball screws. Some of the information is basic, but it also covers preloading and friction. Plus they are promising future articles to expand on the topic. If you prefer to watch a video, you might enjoy the one below.

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Surf’s Up! Virtually

November 1, 2016 by No comments

While it may or may not be true that if everybody had an ocean they’d be surfing like California, it is true that with a water pump, some copper tape, and a few scraps you can make a surfing simulator that sprays you if you don’t keep your balance.

You can see the simple device in operation in the video below. We presume [Adi_10] actually surfs, but we can’t comment on the realism of the simulator. There’s no computer. Just a switch made from the base and the balance board.

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New Lithium Battery Technology Takes Guts

November 1, 2016 by 14 Comments

Researchers have built a prototype lithium-sulphur battery that — when perfected — could have up to five times the energy density of current lithium-ion devices. Researchers in the UK and China drew inspiration from intestines to overcome problems in the battery construction.

In your intestine, small hair-like structures called villi increase the surface area that your body uses to absorb nutrients from food. In the new lithium-sulphur battery, researchers used tiny zinc oxide wires to form a layer of material with a villi-like structure. These villi cover one electrode and can trap fragments of the active material when they break off, allowing them to continue participating in the electrochemical reaction that produces electricity.

Lithium-sulphur batteries aren’t new (in fact, they were used in 2008 in a solar-powered plane that broke several records), but this new technique may make them more practical. You can see a video about ordinary lithium-sulphur batteries below along with more on how this research improves the state of the art.

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SSH Enters The Mosh Pit

November 1, 2016 by 8 Comments

With so many systems depending on Linux, the secure shell SSH has become a staple for many developers. If you are connected to your Raspberry Pi via a cable or a wireless router a few feet away, SSH can provide you with an encrypted connection straight to the box. However, if you have a system out in a swamp somewhere with intermittent slow network access, SSH can be a real pain. When your IP address can change (for example, roaming on a cellular network), SSH has problems, too.

To combat these and other problems, you might consider an open source program called Mosh (mobile shell). There’s two parts to Mosh. One part works as a server while the other is the client application. Neither of these require root access. You can see a video about Mosh below.

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