Flash a Light Bulb, Win a Prize

How many geeks does it take to flash a lightbulb? Judging from the list of entries in the 2017 Flashing Light Prize, so far only seven. But we suspect Hackaday readers can add to that total.

The goal is almost as simple as possible: build something that can flash an incandescent light bulb for at least five minutes. The system actually has to power the bulb’s filament, so no mechanical shutters are allowed. Other than that, the sky is the limit — any voltage, any wattage, any frequency and duty cycle, and any circuit. Some of the obvious circuits, like an RC network on a relay, have been tried. But we assume there will be points for style, in which case this sculptural cascading relay flasher might have a chance. Rube Goldberg mechanical approaches are encouraged, as in this motor, thread, stick and switch contraption. But our fave thus far is the 1000-watt bulb with solar cell feedback by Hackaday regular [mikeselectricstuff].

Get your entry in before August 1st and you’ll be on your way to glory and riches — if your definition of rich is the £200 prize. What the heck, your chances are great right now, and it’s enough for a few pints with your mates. Just don’t let it distract you from working on your 2017 Hackaday Prize entry — we’re currently in the “Wheels, Wings, and Walkers” phase, so maybe there’ll be a little crossover that you can leverage for your flasher.

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Model Sputnik Finds its Voice After Decades of Silence

As we approach the 60th anniversary of the human race becoming a spacefaring species, Sputnik nostalgia will no doubt be on the rise. And rightly so — even though Sputnik was remarkably primitive compared to today’s satellites, its 1957 launch was an inflection point in history and a huge achievement for humanity.

The Soviets, understandably proud of their accomplishment, created a series of commemorative models of Earth’s first artificial moon as gifts to other countries. How one came into possession of the Royal Society isn’t clear, but [Fran Blanche] found out about it through a circuitous route detailed in the video below, and undertook to reproduce the original electronics from the model that made the distinctive Sputnik beeps.

The Royal Society’s version of the model no longer works, but luckily it came with a schematic of the solid-state circuit used to emulate the original’s vacuum-tube guts. Intent on building the circuit as close to vintage as possible and armed with a bag of germanium transistors from the 60s, [Fran] worked through the schematic, correcting a few issues here and there, and eventually brought the voice of Sputnik back to life.

If you think we’ve covered Sputnik’s rebirth before, you may be thinking about our article on how some hams rebuilt Sputnik’s guts from a recently uncovered Soviet-era schematic. [Fran]’s project just reproduces the sound of Sputnik — no license required!

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Ham Goes Nuts for Tiny Transmitter

What’s the minimal BOM for a working amateur radio transmitter? Looks like you can get away with seven parts, or eight if you include the walnut. You’ve got to have a walnut.

Some hams really love the challenge of QRP, or the deliberate use of low-power transmitters to provide a challenge to making long-distance contacts. We’ve covered the world of QRP before and noted that while QRP rigs don’t throw a lot of power, it doesn’t mean that they need to be simple. Some get quite complex and support many different modulation schemes, even digital modes. With only a single 2N3904 transistor,  [Jarno (PA3DMI)]’s tiny transmitter won’t do much more than send Morse using CW modulation, but given that it’s doing so from inside a walnut shell, we have no complaints. The two halves of the shell are hinged together and hold a scrap of perfboard for the simple quartz crystal oscillator. The prototype was tuned outside the shell,  and the 9-volt battery is obviously external, but aside from that it’s nothing but nuts.

We’d love to see [Jarno] add a spring to the hinge and contacts on the shell halves so no keyer is required. Who knows? Castanet-style keying might be all the rage with hams after that.

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Using a Lecher Line To Measure High Frequency

How do you test the oscillator circuit you just made that runs between 200MHz and 380MHz if all you have is a 100MHz oscilloscope, a few multimeters and a DC power supply? One answer is to put away the oscilloscope and use the rest along with a length of wire instead. Form the wire into a Lecher line.

That’s just what I did when I wanted to test my oscillator circuit based around the Mini-Circuits POS-400+ voltage controlled oscillator chip (PDF). I wasn’t going for precision, just verification that the chip works and that my circuit can adjust the frequency. And as you’ll see below, I got a fairly linear graph relating the control voltages to different frequencies.

What follows is a bit about Lecher lines, how I did it, and the results.

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Understanding The Quartz Crystal Resonator

Accurate timing is one of the most basic requirements for so much of the technology we take for granted, yet how many of us pause to consider the component that enables us to have it? The quartz crystal is our go-to standard when we need an affordable, known, and stable clock frequency for our microprocessors and other digital circuits. Perhaps it’s time we took a closer look at it.

The first electronic oscillators at radio frequencies relied on the electrical properties of tuned circuits featuring inductors and capacitors to keep them on-frequency. Tuned circuits are cheap and easy to produce, however their frequency stability is extremely affected by external factors such as temperature and vibration. Thus an RF oscillator using a tuned circuit can drift by many kHz over the period of its operation, and its timing can not be relied upon. Long before accurate timing was needed for computers, the radio transmitters of the 1920s and 1930s needed to stay on frequency, and considerable effort had to be maintained to keep a tuned-circuit transmitter on-target. The quartz crystal was waiting to swoop in and save us this effort.

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A Vintage Single Transistor LED Blinker

[Eric Wasatonic] had a box of SWB2433 transistors that he had very little information about. In order to discover their properties, he fired up his curve tracer to compare these transistors with more common ones. He noticed the SWB2433 exhibited negative resistance while the similar curves of a 2n3904 didn’t. Then he reverse-biased the two transistors: the negative resistance region on the 2n3904 was less than that of the SWB2433, but it was there, and a 2n2222 had a bigger region. Using this knowledge, he developed a relaxation oscillator circuit which uses a negatively biased transistor.

Using one transistor, one resistor and one capacitor, he describes the circuit and how the components affect the frequency of the sawtooth wave the oscillator creates. [Eric] uses the oscillator to build a simple LED blinker and shows what happens when he changes the transistor and adjusts the voltage or resistance. He also shows the circuit as a tone generator and adjusts the tone by replacing the resistor with a potentiometer. And then, for fun, he modifies the circuit to show the oscillator as an AM transmitter. Check out his video after the break.

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Soft Robot With Microfluidic Logic Circuit

Perhaps our future overlords won’t be made up of electrical circuits after all but will instead be soft-bodied like ourselves. However, their design will have its origins in electrical analogues, as with the Octobot.

The Octobot is the brainchild a team of Harvard University researchers who recently published an article about it in Nature. Its body is modeled on the octopus and is composed of all soft body parts that were made using a combination of 3D printing, molding and soft lithography. Two sets of arms on either side of the Octobot move, taking turns under the control of a soft oscillator circuit. You can see it in action in the video below.

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