Make Your Own Microdot

July 3, 2020 by Jenny List 28 Comments

If you spent your youth watching James Bond or similar movies on rainy Saturday afternoons, then you may be familiar with a microdot as a top-secret piece of spy equipment, usually revealed as having been found attached to a seemingly innocuous possession of one of the bad guy’s henchmen, which when blown up on the screen delivers the cryptic yet vital clue to the location of the Evil Lair. Not something you give much thought in 2020 you might think, but that’s reckoning without [Sister HxA], who has worked out how to make them herself and detailed the process in a Twitter thread.

A microdot is a tiny scrap of photographic film, containing the image of some secret document or other, the idea being that it is small enough to conceal on something else. The example she gives is hiding it underneath a postage stamp. Because of their origins in clandestine work there is frustratingly little info on how to produce them, but she found a set of British instructions. Photographing a sheet such that its image occupies a small portion of her negative she makes a postage-stamp-sized one, and with care photographing that she manages to produce another of only a few millimetres in size. The smaller one isn’t very legible, but it’s still a fascinating process.

While we’re shopping at Q branch, how about an air-gun pen worthy of James Bond?

Watch Conway’s Game Of Life Flutter Across A Flip-Dot Display

July 2, 2020 by Donald Papp 21 Comments

Like many of us, [John Whittington] was saddened with the news that John Horton Conway passed away a little earlier this year, and in honor of his work, he added the Game of Life to a flip-dot display that he has been working on. The physicality of an electromechanical display seems particularly fitting for cellular automata.

Like what you see? If you’re curious about what makes it all tick, the display shown is an Alfa-Zeta XY5 28×14 but [John] is currently working on building them into a much larger 256 x 56 display. GitHub hosts the flip-dot simulator and driver software [John] is using, and the Game of Life functions are here.

If you’re new to the Game of Life and are not really sure what you’re looking at, [Elliot Williams] tells you all you need to know in his writeup celebrating its profound impact and lasting legacy. Watch the flip-dot display in action in the video embedded below.

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Reliving Heathkit’s Glory Days Through A Teardown And Rebuild

June 26, 2020 by Dan Maloney 10 Comments

In its heyday, the experience offered by the Heath Company was second to none. Every step of the way, from picking something out of the Heathkit catalog to unpacking all the parts to final assembly and testing, putting together a Heathkit project was as good as it got.

Sadly, those days are gone, and the few remaining unbuilt kits are firmly in the unobtanium realm. But that doesn’t mean you can’t tear down and completely rebuild a Heathkit project to get a little taste of what the original experience was like. [Paul Carbone] chose a T-3 Visual-Aural signal tracer, a common enough piece that’s easy to find on eBay at a price mere mortals can afford. His unit was in pretty good shape, especially for something that was probably built in the early 1960s. [Paul] decided that instead of the usual recapping, he’d go all the way and replace every component with fresh ones. That proved easier said than done; things have changed a lot in five decades, and resistors are a lot smaller than they used to be. Finding hookup wire to match the original was also challenging, as was disemboweling some of the electrolytic cans so they could be recapped. The finished product is beautiful, though — even the Magic Eye tube works — and [Paul] reports that the noise level is so low he wasn’t sure if turned it on at first.

We’ve covered the rise and fall of Heathkit, as well as their many attempted comebacks, including an inexplicable solder-free radio and the “world’s most reliable” clock. Looking at these offerings, we think [Paul] may be onto something here.

Decapsulating A Dual Triode

June 21, 2020 by Al Williams 8 Comments

We see quite a bit of work where people decapsulate ICs or other solid state devices to expose their inner workings. But how about hollow state? [Tomtektest] had a dual triode that has lost its vacuum integrity — gone to air, as he calls it — and decided to open it up to better expose its inner workings. (Video, embedded below.)

Of course, you can always see the innards through the glass, but it is interesting to have the envelope out of the way. Apparently, how you remove the glass is a bit tricky if you don’t want to damage the working bits as you remove it.

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Chasing A Long-Obsolete Tube

June 20, 2020 by Jenny List 12 Comments

Regular readers will know that here at Hackaday we have a penchant for poking fun at the more silly end of the audiophile world, with its dubious accessories and purple prose. It’s worth remembering though that this is not representative of the whole discipline of audio design, indeed the quest for perfect audio reproduction contains plenty of complex engineering problems.

We’re indebted to [macsimski] then for sending us a link to a page from Phaedrus Audio from a year or two ago, in which they discuss the history of an unusual pentode tube used as an impedance converter in a series of legendary post-war microphones. It’s unlikely that you’ll have a Neumann U47 or U48 broadcast microphone on your bench, but even so the story behind their design is one that should fascinate anyone.

It takes us back to the period immediately following the Second World War, when German electricity supplies were varied and unreliable, and radio receivers designed for them required new tubes from the manufacturers. Among these was the VF14, with an unusual high-voltage heater designed such that two of them could be connected in series across the supply. This and its compact shape prompted its selection for the professional microphones, even though its performance was so poor that only a third of the production passed the performance test.

Since it passed out of production in the early 1950s the remaining components are extremely rare, and the majority of those surviving do not meet the performance characteristics of the microphone. The Phaedrus write-up goes into significant technical detail which should be of note to anyone with an interest in tubes, and ends up with their reason for it all, a plug-in hardware simulation of the original tube’s properties. Vintage capacitor microphones may be out of the ordinary for Hackaday, but it’s still a good read.

For a bit more on capacitor microphones it’s worth a look at our dive into electrets.

Header image: JacoTen / CC BY-SA 3.0

Fail Of The Week: How Not To Watercool A PC

June 17, 2020 by Dan Maloney 50 Comments

To those who choose to overclock their PCs, it’s often a “no expense spared” deal. Fancy heat sinks, complicated liquid cooling setups, and cool clear cases to show off all the expensive guts are all part of the charm. But not everyone’s pockets are deep enough for off-the-shelf parts, so experimentation with cheaper, alternatives, like using an automotive fuel pump to move the cooling liquid, seems like a good idea. In practice — not so much.

The first thing we thought of when we saw the title of [BoltzBrain]’s video was a long-ago warning from a mechanic to never run out of gas in a fuel-injected car. It turns out that the gasoline acts as a coolant and lubricant for the electric pump, and running the tank dry with the power still applied to the pump quickly burns it out. So while [BoltzBrain] expected to see corrosion on the brushes from his use of water as a working fluid, we expected to see seized bearings as the root cause failure. Looks like we were wrong: at about the 6:30 mark, you can see clear signs of corrosion on the copper wires connecting to the brushes. It almost looks like the Dremel tool cut the wire, but that green copper oxide is the giveaway. We suspect the bearings aren’t in great shape, either, but that’s probably secondary to the wires corroding.

Whatever the root cause, it’s an interesting tour inside a common part, and the level of engineering needed to build a brushed motor that runs bathed in a highly flammable fluid is pretty impressive. We liked the axial arrangement of the brushes and commutator especially. We wonder if fuel pumps could still serve as a PC cooler — perhaps changing to a dielectric fluid would do the trick.

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Overclocking And Watercooling The TI-84, Just Cause

June 16, 2020 by Lewin Day 23 Comments

The TI-84 is an enduring classic – the calculator that took many through high school, college and beyond. A hacker’s favorite, it’s been pushed to the limits in all sorts of ways. The crew at [Linus Tech Tips] decided to join in the fun, overclocking a TI-84 Plus and adding water cooling to boot.

The TI-84 uses a simple resistor capacitor circuit to generate its clock, making it overclocking it a cinch. By changing the resistor value in the circuit, the clock can be made to run faster. The team have some issues with pads delaminating from the PCB, but manage to sub in a trimpot which lets the clock be changed on the fly. A boost of 10MHz over stock gets the calculator operating at 26MHz, with notably quicker performance in the TI port of Doom 2. Without accurate measurement of CPU temps, it’s hard to say whether watercooling the calculator is justified. However, the team do a great job of entirely overengineering the solution, with a custom-made cooling block hooked up to a massive spherical reservoir.

With the stability issues inherent in overclocking, and the unwieldy watercooling tubes, it’s not a good hack in the practicality sense. It is, however, quite amusing, and that’s always worth something. TI calculators have long been targets for hackers, and you can even get them online if you so desire. Video after the break.

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