Arcade Track-Mouse

[Evan] always wanted a trackball for his arcade cabinet. It’s hard to play Missile Command with anything else, and Centipede with any other controller is just stupid. So he bought one, jury-rigged a mounting bracket for it, and then fried it by plugging the wiring harness in backwards. Doh!

But proving Edison’s famous statement that innovation is 1% inspiration and 99% having the right stuff in your junk bin, [Evan] dug deep and came out with one of twenty (!) old ball mice that he had purchased for just such an occasion. (Yeah, right.) Since a ball mouse is essentially an upside-down trackball, all that remained for him to do was reverse-engineer the mouse and swap its controller in for the busted trackball.

A simple hack, born of necessity, and well done. If you’re stuck with a crate of optical mice instead, consider turning them instead into optical laser rangefinders.

Capacitors Made Easy The Hackaday Way

If you build electronic circuits on a regular basis the chances are you will have used capacitors many times. They are a standard component along with the resistor whose values are lifted off the shelf without a second thought. We use them for power supply smoothing and decoupling, DC blocking, timing circuits, and many more applications.

Different capacitor applications. By Elcap (Own work) [CC0], via Wikimedia Commons
Different capacitor applications. By Elcap (Own work) [CC0], via Wikimedia Commons
A capacitor though is not simply a blob with two wires emerging from it and a couple of parameters: working voltage and capacitance. There is a huge array of capacitor technologies and materials with different properties. And while almost any capacitor with the right value can do the job in most cases, you’ll find that knowing more about these different devices can help you make something that doesn’t just do the job, but does the best possible job. If you’ve ever had to chase a thermal stability problem or seek out the source of those extra dBs of noise for example you will appreciate this.

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Hands-On With The BBC Micro:Bit

It’s been a long wait, but our latest single board computer for review is finally here! The BBC micro:bit, given free to every seventh-grade British child, has landed at Hackaday courtesy of a friend in the world of education. It’s been a year of false starts and delays for the project, but schools started receiving shipments just before the Easter holidays, pupils should begin lessons with them any time now, and you might even be able to buy one for yourself by the time this article goes to press.

The micro:bit top view
The micro:bit top view

It’s a rather odd proposition, to give an ARM based single board computer to coder-newbie children in the hope that they might learn something about how computers work, after all if you are used to other similar boards you might expect the learning curve involved to be rather steep. But the aim has been to position it as more of a toy than the kind of development board we might be used to, so it bears some investigation to see how much of a success that has been.

Opening the package, the micro:bit kit is rather minimalist. The board itself, a short USB lead, a battery box and a pair of AAA cells, an instruction leaflet, and the board itself.  Everything is child-sized, the micro:bit is a curved-corner PCB about 50mm by 40mm. The top of the board has a 5 by 5 square LED matrix and a pair of tactile switches, while the bottom has the surface-mount processor and other components, the micro-USB and power connectors, and a reset button. Along the bottom edge of the board is a multi-way card-edge connector for the I/O lines with an ENIG finish. On the card edge connector several contacts are brought out to wide pads for crocodile clips with through-plated holes to take 4mm banana plugs, these are the ground and 3V power lines, and 3 of the I/O lines.

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Hackaday Prize Entry: You Know, For Kids

Like the fictitious invention of the Hula Hoop in Hudsucker Proxy, [David Spinden]’s big idea is small and obvious once you’ve seen it. And we’re not saying that’s a bad thing at all. What he’s done is to make a new kind of prototyping connector; one that hooks into a through-plated hole like a pogo pin, but in the horizontal direction.

9092981463539177581This means that your test-points can do double duty as header connectors, when you need to make something more permanent, or vice-versa. That’s a lot of flexibility for a little wire, and it takes one more (mildly annoying) step out of prototyping — populating headers.

[David] makes them out of readily available header pins that already have the desired spring-like profile, and simply cuts them out and connects them to a standard Dupont-style hookup wire. Great stuff.

When we opened up the “Anything Goes” category for the Hackaday Prize, we meant it. We’re excited to see people entering large and small ideas that improve the world, even if it’s just the world of hackers.

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Making Springs At Home

[This Old Tony] teaches us how to make springs on a lathein this video done in the style of How It’s Made. Mixed in with snark, in his usual style, is a lot of useful information.

The Machinery’s Handbook certainly has all the information one would need to design the basic spring shapes, but it’s not always necessary. [Tony] points out that cheating is entirely acceptable. For example, if you need a spring that’s close to the dimensions of a standard spring, simply copy over the values from the standard spring. He explains all the terminology needed to decrypt the pages in your engineering tome of choice.

He shows the basics of winding a spring on a mandrel (or that round metal thing, if you want to use the industry term). First wind the inactive coils, then set your lathe to the desired spring pitch. Engage it as if threading, then disengage and wind the final inactive coils. A quick trip to the sander squares the ends of a standard coil spring. However, the tools can also be used to make torsion springs, or even exotic combination springs.

For a good… educational laugh, watch the whole video after the break.

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Dragging Teletypes Into The 21st Century

If you are of a certain age you may have worked in an office in the days before the computer revolution, and the chances are that in the corner of your office there would have been a teletype machine. Like a very chunky typewriter with a phone attached, this was an electromechanical serial terminal and modem, and machines like it would have formed the backbone of international commerce in the days before fax, and then email.

Teletypes may have disappeared from the world of trade, but there are a surprising number still in private hands. Enthusiasts collect and restore them, and radio amateurs still use digital modes based on their output. The problem facing today’s teletype owner though is that they are becoming increasingly difficult to interface to a modern computer. The serial port, itself an interface with its early history in the electromechanical world, is now an increasingly rare sight.

[Eric] has a project which addresses the teletype owner’s interfacing woes, he’s created a board with all the necessary level shifters and an Atmega32u2 microcontroller to translate the teletype’s output to USB.

In his design he’s had to solve a few problems related to such an aged interface. Teletypes have a serial output, but it’s not the TTL or RS232 we may be used to. Instead it’s a high-voltage current loop designed to operate electromagnets, so his board has to incorporate an optocoupler to safely isolate the delicate computer circuitry. And once he had the teletype’s output at a safe level he then had to translate its content, teletypes speak 5-bit ITA2 code rather than our slightly newer 7-bit ASCII.

The result though is a successful interface between teletype and computer. The former sees another teletype, while the latter sees a serial terminal. If you have a teletype and wish to try it for yourself, he’s released the source code in a GitHub repository.

Teletypes have featured a few times here at Hackaday over the years. We’ve had one as an SMS client, another that monitors a Twitter feed, and while it’s not strictly a teletype, a close examination of an Olivetti mechanical serial terminal.

Arduino Motion Detection With A Bit Of Wire

It is likely that many of us will at some time have experimented with motion detectors. Our Arduinos, Raspberry Pis, Beaglebones or whatever will have been hooked up to ultrasonic or PIR boards which will have been queried for their view of what is in front of them.

[Connornishijima] has stumbled on a different way to detect motion with an Arduino, he’s polling an ADC pin with a simple length of twisted pair hooked up to it and earth, and reliably generating readings indicating when he (or his cat) is in its vicinity. He’s calling the effect “Capacitive turbulence”, and he’s open to suggestions as to its mechanism. He can only make it work on the Arduino, other boards with ADCs don’t cut it.

Frequent Hackaday featuree [Mitxela] may have also discovered something similar, and we’ve hesitated to write about it because we didn’t understand it, but now it’s becoming unavoidable.

It’s always dangerous in these situations to confidently state your opinion as “It must be…” without experimental investigation of your own. Those of us who initially scoffed at the idea of the Raspberry Pi 2 being light sensitive and later had to eat their words have particular cause to remember this. But this is an interesting effect that bears understanding. We would guess that the Arduino’s fairly high input impedance might make it sensitive to mains hum, if you did the same thing to an audio amplifier with a phono input you might well hear significant hum in the speaker as your hand approached the wire. It would be interesting to try the experiment at an off-grid cabin in the woods, in the absence of mains hum.

If you’d like to give his experiment a try, he’s posted his sketch on Pastebin. And he’s put up the video below the break demonstrating the effect in action, complete with cats.

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