My Most Obsolete Skill: Delta-Gun Convergence

April 4, 2016 by Jenny List 92 Comments

In a lifetime of working with electronics we see a lot of technologies arrive, become mighty, then disappear as though they had never been. The germanium transistor for instance, thermionic valves (“tubes”), helical-scan video tape, or the CRT display. Along the way we pick up a trove of general knowledge and special skills associated with working on the devices, which become redundant once the world has moved on, and are suitable only reminiscing about times gone by.

When I think about my now-redundant special skills, there is one that comes to the fore through both the complexity and skill required, and its complete irrelevance today. I’m talking about convergence of the delta-gun shadow mask colour CRTs that were the height of television technology until the 1970s, and which were still readily available for tinkering purposes by a teenager in the 1980s.
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DVB-S From A Raspberry Pi With No Extra Hardware

April 3, 2016 by Jenny List 19 Comments

An exciting aspect of the trend in single board computers towards ever faster processors has been the clever use of their digital I/O with DSP software to synthesize complex signals in the analogue and RF domains that would previously have required specialist hardware. When we use a Raspberry Pi to poll a sensor or flash an LED it’s easy to forget just how much raw processing power we have at our fingertips.

One of the more recent seemingly impossible feats of signal synthesis on a Raspberry Pi comes from [Evariste Courjaud, F5OEO]. He’s created a DVB-S digital TV transmitter that produces a usable output direct from a GPIO pin, with none of the external modulators that were a feature of previous efforts required. (It is worth pointing out though that for legal transmission a filter would be necessary.)

DVB is a collection of digital TV standards used in most of the world except China and the Americas. DVB-S is the satellite version of DVB, and differs from its terrestrial counterpart in the modulation scheme it employs. [Evariste] is using it because it has found favor as a digital mode in amateur radio.

This isn’t the first piece of [F5OEO] software creating useful radio modes from a GPIO pin. He’s also generated SSB, AM, and SSTV from his Pi, something which a lot of us in the amateur radio community have found very useful indeed.

We’ve covered digital TV creation quite a few times in the past on these pages, from the first achievement using a PC VGA card almost a decade ago to more recent Raspberry Pi transmitters using a USB dongle and a home-built modulator on the GPIO pins. Clever signal trickery from digital I/O doesn’t stop there though, we recently featured an astoundingly clever wired Ethernet hack on an ESP8266, and we’ve seen several VHF NTSC transmitters on platforms ranging from the ESP to even an ATtiny85.

Thanks [SopaXorzTaker] for the nudge to finally feature this one.

Raspberry Pi As Speed Camera

April 3, 2016 by Jenny List 110 Comments

Wherever you stand on the topics of road safety and vehicle speed limits it’s probably fair to say that speed cameras are not a universally popular sight on our roads. If you want a heated argument in the pub, throw that one into the mix.

But what if you live in a suburban street used as a so-called “rat run” through route, with drivers regularly flouting the speed limit by a significant margin. Suddenly the issue becomes one of personal safety, and all those arguments from the pub mean very little.

[Gregtinkers]’ brother-in-law posted a message on Facebook outlining just that problem, and sadly the local police department lacked the resources to enforce the limit. This set [Gregtinkers] on a path to document the scale of the problem and lend justification to police action, which led him to use OpenCV and the Raspberry Pi camera to make his own speed camera.

The theory of operation is straightforward, the software tracks moving objects along the road in the camera’s field of view, times their traversal, and calculates the resulting speed. The area of the image containing the road is defined by a bounding box, to stop spurious readings from birds or neighbours straying into view.

He provides installation and dependency instructions and a run-down of the software’s operation in his blog post, and the software itself is available on his GitHub account.

We’ve had a lot of OpenCV-based projects but haven’t featured a speed camera before here on Hackaday. But we have had a couple of dubious countermeasures, like that humorous attempt at an SQL injection attack, or a flash-based countermeasure.

A Keypad Joypad For Your Retro Gaming

April 1, 2016 by Jenny List 15 Comments

[TK] is a retro computer enthusiast who’s had some difficulty locating a joystick for his trusty Amiga 500. New ‘sticks are expensive, and battered survivors from the 80s go for more than they should.

Happily these old controllers were simple devices, having only five control lines for the four directions and a fire button which were active low. [TK] therefore cast around the available components and decided to craft his own controller from a numerical keypad.

Numerical keypads may be ubiquitous, but they’re not the perfect choice for a joypad. Instead of individual switches, they are wired as a matrix. [TK]’s controller works within that constraint without butchering the keypad PCB, though his layout has the left and right buttons below the up and down buttons. Looking at the schematic we wonder whether the 4-5-6 and 7-8-9 rows could be transposed , though joypad layout is probably a matter of personal choice.

Making the controller was a simple case of wiring the pad to a 9-pin D socket in the correct order, and plugging it into the Commodore. He reports that it’s comfortable to use and better than some of the lower-quality joysticks that were on the market back in the day. Veterans of Amiga gaming will understand that sentiment, there were some truly shocking offerings to be had at the time.

Quite a few home-made game controllers have made it onto these pages over the years. There is this one using tactile switches and a ballpoint pen, and a stick made from the idler wheel from a surplus VCR, but the ultimate crown of junkbox joysticks should go to this joystick made from clothes pins. If we take one thing away from all this home-made controller ingenuity, it is that what really matters is not the hardware but the gameplay.

Co-Exist With Your Coax: Choose The Right Connector For The Job

March 31, 2016 by Jenny List 66 Comments

Just a selection from the author's unholy assortment of adaptors. — Just a selection from the author’s unholy assortment of adaptors.

If you do any work with analogue signals at frequencies above the most basic audio, it’s probable that somewhere you’ll have a box of coax adaptors. You’ll need them, because the chances are your bench will feature instruments, devices, and modules with a bewildering variety of connectors. In making all these disparate devices talk to each other you probably have a guilty past: at some time you will have created an unholy monster of a coax interface by tying several adaptors together to achieve your desired combination of input and output connector. Don’t worry, your secret is safe with me.

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Intel Ups The Dev Board Ante With The Quark D2000

March 31, 2016 by Jenny List 74 Comments

Intel have a developer board that is new to the market, based on their Quark (formerly “Mint Valley”) D2000 low-power x86 microcontroller. This is a micropower 32-bit processor running at 32MHz, and with 32kB of Flash and 8kB of RAM. It’s roughly equivalent to a Pentium-class processor without the x87 FPU, and it has the usual impressive array of built-in microcontroller peripherals and I/O choices.

The board has an Arduino-compatible shield footprint, an FTDI chip for USB connectivity, a compass, acceleration, and temperature sensor chip, and a coin cell holder with micropower switching regulator. Intel provide their own System Studio For Microcontrollers dev environment, based around the familiar Eclipse IDE.

Best of all is the price, under $15 from an assortment of the usual large electronics wholesalers.

This board joins a throng of others in the low-cost microcontroller development board space, each of which will have attributes that its manufacturers will hope make it stand out. Facing such competition the Intel board will have to be something rather special to achieve that aim, so why should it excite your interest? We would point to the low price, the x86 code if that is your flavour of choice, and the relatively tiny power consumption.

Stepping back from the dev board for a moment, consider this processor as an illustration of technological progress in semiconductor fabrication. Over twenty years ago this chip’s Pentium ancestor ran on 5 volts and got so hot you could fry an egg on it, here is a Pentium that can run on a few milliwatts from a coin cell. Fortunately you won’t be running Windows 95 on it though.

We’re sure we’ll see plenty of projects here in the future using the Quark. Intel’s previous effort in this space, the Edison, has made several appearances. We’ve covered its launch in 2014, looked at someone running Doom on it, and examined its use with audio effects.

Thanks [Nolan M] for the tip.

A Ridiculous Way To Light An LED: Candle-power

March 30, 2016 by Jenny List 32 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.