A Ridiculous Way To Light An LED: Candle-power

March 30, 2016 by Jenny List 31 Comments

If you have ever entertained yourself by reading comprehensive electronic-theory textbooks you’ll have seen references to technologies that sound really interesting but which you will rarely hold in your hand. They may be dead-ends that have been superseded by more recent innovations, or they may be technologies that have found uses but in other fields from those in which they originally showed promise. What if you could take these crazy parts and actually build something?

[Fedetft] has an interesting project that combines two of those intriguing textbook references, he’s created a thermopile that lights an LED through an inverter whose oscillator is a tunnel diode. Dig out the textbook.

If you’ve used a thermocouple thermometer or a semiconductor thermoelectric generator then you’ll have encountered the thermoelectric effect. Perhaps you’ve even operated a Peltier cooling element in this mode. When a circuit is made with two junctions between different types of conductor with a temperature difference between the two junctions, a current will flow in the circuit which is dependent on both the scale of the temperature difference and the properties of the conductors.

A thermopile is a collection of these thermoelectric junction circuits between metal conductors, arranged in series to increase the voltage. [Fedetft]’s thermopile uses chromel and alumel wires taken from a K-type thermocouple. He’s made six sets of junctions, and supported them with small pieces of mica sheet. Using the heat from a candle he found he could generate about 200mV with it, at about 3.7mW.

Such a tiny source of electricity would be of little use to light an LED directly, so he needed to build an inverter. And that’s where the tunnel diode comes in. Tunnel diodes have a negative-resistance region that can be used to amplify and oscillate at extremely high frequencies in extremely simple circuits, yet they’re not exactly a device you’d encounter very often in 2016. [Fedetft] has a Russian tunnel diode, and he’s used it with a toroidal transformer in an inverter circuit he found in an RCA tunnel diode manual from 1963. It’s a two-component Joule Thief. The RCA manual is a good read in itself for those curious about tunnel diodes.

The resulting circuit produces a 15kHz oscillation with 4.5v peaks, and has just enough power to light an LED.

While it might seem pointless to barely light an LED from a brightly lit candle, the important part of [Fedetft]’s project is to gain some understanding of two of those technological backwaters from the textbooks. And we applaud that.

It’s the mark of a truly esoteric technology that it features rarely on Hackaday, and neither of these two disappoint. We’ve only mentioned tunnel diode in passing when looking at diodes in general, and we’ve tended to use “thermopile” in another sense to refer to thermal imaging cameras.

An Excellent Primer For Sketching Mechanical Drawings

March 30, 2016 by James Hobson 38 Comments

Mechanical drawings are an excellent way to convey design information, and while sophisticated 3D modeling is slowly taking over, with some companies accepting files over drawings, the mechanical drawing remains the written contract so to speak for complex parts with tolerances and non-modeled features.

But if you didn’t take a technical drawing class (typically Engineering Drawings 101), how do you learn? Well, if you have 15 minutes, this is an excellent video, which speaking from experience, covers the basics from the 101 course.

The lesson covers all the basics, from 2D projection, multi-view drawings, isometric projection, cross sectioning, linear dimensioning, basic tolerancing and alternate views.

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Windows And Ubuntu: “Cygwin Can Suck It”

March 30, 2016 by Brian Benchoff 229 Comments

For the last ten years or so, computing has been divided into two camps: Windows, and everything else with a *nix suffix. Want a computing paradigm where everything is a file? That’s Linux. Want easy shell scripting that makes the command line easy? Linux. Want a baroque registry with random percent signs and dollar symbols? That would be Windows. Want to run the most professional productivity apps for design and engineering? Sadly, that’s Windows as well.

*nix runs nearly the entire Internet, the top 500 supercomputers in the world, and is the build environment for every non-Windows developer. Yet Windows is the most popular operating system. The divide between Windows and *nix isn’t so much a rivalry, as much as people who still spell Microsoft with a dollar sign would tell you. It’s just the way personal computing evolved by way of legacy apps and IT directors.

Now, this great divide in the world of computing is slowly closing. At Microsoft’s Build 2016 developer’s conference, Microsoft and Canonical, Ubuntu’s parent company, announced a partnership that will allow Ubuntu to run using native Windows libraries.

In short, this announcement means bash and the Linux command line is coming to Windows 10. The command line is great, but userland is where it’s at, and here this partnership really shines. Unlike Cygwin, the current way to get *nix stuff running in a Windows environment, Windows’ bash will allow unmodified Linux programs to run unmodified on Windows 10.

It is not an understatement to say this is the most important development in operating systems in the last 10 years. For the last decade, every developer who is not purely a Windows developer has picked up a MacBook for the sole reason of having BSD under the hood. If you’re looking for a reason Apple is popular with devs, it’s *nix under the hood. This announcement changes all of that.

Lazy Bluetooth: Build With BLE, Don’t Reinvent It

March 30, 2016 by Al Williams 21 Comments

It is a good bet that you have at least one Bluetooth device hanging around. Headsets, mice, keyboards, and speakers have become increasingly common. Bluetooth forms a short range wireless network and can also perform file transfers and create virtual serial ports.

If you have ever had to stop listening to music to recharge a Bluetooth headphone, you know Bluetooth won’t run long on batteries. In 2006, Nokia introduced Wibree, which would later become Bluetooth Low Energy (or BLE). These days it’s used in everything and it’s well worth your time to gather a basic understanding of this technology.

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Peering Inside The GPU Black Box

March 30, 2016 by Elliot Williams 27 Comments

Researchers at Binghamton University have built their own graphics processor unit (GPU) that can be flashed into an FGPA. While “graphics” is in the name, this GPU design aims to provide a general-purpose computing peripheral, a GPGPU testbed. Of course, that doesn’t mean that you can’t play Quake (slowly) on it.

The Binghamton crew’s design is not only open, but easily modifiable. It’s a GPGPU where you not only know what’s going on inside the silicon, but also have open-source drivers and interfaces. As Prof. [Timothy Miller] says,

It was bad for the open-source community that GPU manufacturers had all decided to keep their chip specifications secret. That prevented open source developers from writing software that could utilize that hardware. With contributions from the ‘open hardware’ community, we can incorporate more creative ideas and produce an increasingly better tool.

That’s where you come in. [Jeff Bush], a member of the team, has a great blog with a detailed walk-through of a known GPU design. All of the Verilog and C++ code is up on [Jeff]’s GitHub, including documentation.

If you’re interested in the deep magic that goes on inside GPUs, here’s a great way to peek inside the black box.

FBI Vs Apple: A Postmortem

March 30, 2016 by Elliot Williams 92 Comments

By now you’ve doubtless heard that the FBI has broken the encryption on Syed Farook — the suicide terrorist who killed fourteen and then himself in San Bernardino. Consequently, they won’t be requiring Apple’s (compelled) services any more.

A number of people have written in and asked what we knew about the hack, and the frank answer is “not a heck of a lot”. And it’s not just us, because the FBI has classified the technique. What we do know is that they paid Cellebrite, an Israeli security firm, at least $218,004.85 to get the job done for them. Why would we want to know more? Because, broadly, it matters a lot if it was a hardware attack or a software attack.

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Rotary Subwoofer Combines A Speaker Coil W/ A Fan

March 30, 2016 by James Hobson 55 Comments

What happens when you combine a fan with a sub-woofer? Apparently, you get a high-efficiency ultra low hertz (3-5hz) rotary subwoofer!

First thing’s first, believe it or not, these things really do exist. [Chris] got the idea to build his own after seeing the TRW-17, a commercial offering of a rotary subwoofer.

The concept is pretty simple. If you use a giant subwoofer, you can get low frequency response, but it uses an immense amount of power to move a giant speaker coil. So what if you put something on a smaller speaker coil to increase airflow? Like, a fan or something?

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