Fail Of The Week: The SMD Crystal Radio That Wasn’t

December 3, 2024 by Dan Maloney 18 Comments

The crystal radio is a time-honored build that sadly doesn’t get much traction anymore. Once a rite of passage for electronics hobbyists, the classic coil-on-an-oatmeal-carton and cat’s whisker design just isn’t that easy to pull off anymore, mainly because the BOM isn’t really something that you can just whistle up from DigiKey or Mouser.

Or is it? To push the crystal radio into the future a bit, [tsbrownie] tried to design a receiver around standard surface-mount inductors, and spoiler alert — it didn’t go so well. His starting point was a design using a hand-wound air-core coil, a germanium diode for a detector, and a variable capacitor that was probably scrapped from an old radio. The coil had three sections, so [tsbrownie] first estimated the inductance of each section and sourced some surface-mount inductors that were as close as possible to their values. This required putting standard value inductors in series and soldering taps into the correct places, but at best the SMD coil was only an approximation of the original air-core coil. Plugging the replacement coil into the crystal radio circuit was unsatisfying, to say the least. Only one AM station was heard, and then only barely. A few tweaks to the SMD coil improved the sensitivity of the receiver a bit, but still only brought in one very local station.

[tsbrownie] chalked up the failure to the lower efficiency of SMD inductors, but we’re not so sure about that. If memory serves, the windings in an SMD inductor are usually wrapped around a core that sits perpendicular to the PCB. If that’s true, then perhaps stacking the inductors rather than connecting them end-to-end would have worked better. We’d try that now if only we had one of those nice old variable caps. Still, hats off to [tsbrownie] for at least giving it a go.

Note: Right after we wrote this, a follow-up video popped up in our feed where [tsbrownie] tried exactly the modification we suggested, and it certainly improves performance, but in a weird way. The video is included below if you want to see the details.

Continue reading “Fail Of The Week: The SMD Crystal Radio That Wasn’t” →

A Brief History Of Calculator Watches

December 2, 2024 by Al Williams 32 Comments

When humans counted on their fingers, everyone had a state-of-the-art (at the time) calculator at all times. But as we got smarter about calculation, we missed that convenience. When slide rules were king, techies were known to carry them around like swords swinging from their belts. These were replaced with electronic calculators, some also swinging from belt loops, but no matter how small they were, they still were not that handy, no pun intended. That changed around 1975. The Time Computer Calculator company produced an amazing calculator watch for Pulsar. At the time, Pulsar was a brand of the Hamilton Watch Company.

A Pulsar calculator watch (photo: The Smithsonian)

There were a few problems. First, the watch was thick. Despite its size, it had tiny keys, so you had to use a little stylus to push the keys — not as handy as you might wish. On top of that, 1975 display technology used power-hungry LEDs. So, the display was prone to turning off quickly, and the batteries died quickly.

Unsurprisingly, Hamilton, in conjunction with Electro/Data, had earlier rolled out the first LED watch in 1972. With an 18-karat gold case, it went for a cool $2,100 — a whole lot of money in 1972. The first calculator watch was also gold and went for almost $4,000. Soon, though, they brought out a stainless and a gold-filled version that came in at under $500.

Continue reading “A Brief History Of Calculator Watches” →

Hackaday Podcast Episode 298: Forbidden USB-C, A Laser Glow-o-Scope, And The Epoch Super Cassette Vision

November 29, 2024 by Jenny List 5 Comments

This week’s Hackaday podcast has a European feel, as Elliot Williams is joined by Jenny List for a look at the week’s happenings in the world of cool hardware hacks. Starting with the week’s news, those Redbox vending machines continue to capture the attention of hackers everywhere, and in the race to snag one before they’re carted off for recycling someone has provided the missing hardware manual in the form of a wiki. Europeans can only look on wistfully. Then there’s the curious case of life on the asteroid sample, despite the best efforts of modern science those pesky earth bacteria managed to breach all their anti-contamination measures. Anyone who’s had a batch of homebrew go bad feels their pain.

The week provided plenty of hacks, with the team being wowed by [Bitluni]’s CRT-like laser projector, then the many ingenious ways to 3D-print a hinge, and perhaps one of the most unforgiving environments in the home for a piece of robotics. Meanwhile our appetite for cool stuff was sated by an entire family of Japanese games consoles we’d never heard of, and the little voltage reference whose data sheet also had an audio amplifier circuit. Finishing up, our colleague Arya has many unorthodox uses for a USB-C cable, and we have a frank exchange of views about Linux audio.

Give it a listen below and check out all the links, and by all means, give us a roasting in the comments!

Continue reading “Hackaday Podcast Episode 298: Forbidden USB-C, A Laser Glow-o-Scope, And The Epoch Super Cassette Vision” →

FLOSS Weekly Episode 811: Elixir & Nerves – Real Embedded Linux

November 27, 2024 by Jonathan Bennett 1 Comment

This week, Jonathan Bennett and Lars Wikman chat about Elixir and Nerves — a modern language that’s a take on Erlang, and an embedded Linux approach for running Elixir code on devices.

Subscribe to catch the show live, and come to Hackaday for the rest of the story!

Continue reading “FLOSS Weekly Episode 811: Elixir & Nerves – Real Embedded Linux” →

Could Nuclear Be The Way To Produce Synthetic Fuel On The Cheap?

November 27, 2024 by Lewin Day 127 Comments

Fossil fuels can be a bit fussy to access, and geopolitics tends to make prices volatile. Burning them also takes carbon out of the ground and puts it into the atmosphere, with undesirable climate implications. The hunt for a solution has been on for quite some time.

Various synthetic fuels have been proposed as a solution, wherein carbon dioxide is captured from the air and chemically processed into useful fuel. Done properly, this could solve the climate issue where any fuel burned has its carbon later captured to make more fuel. The problem, though, is that this process is very energy intensive. Given the demands, it’s no surprise that some are looking towards nuclear reactors for the answer.

Continue reading “Could Nuclear Be The Way To Produce Synthetic Fuel On The Cheap?” →

Retrotechtacular: The Deadly Shipmate

November 27, 2024 by Dan Maloney 33 Comments

During World War II, shipboard life in the United States Navy was a gamble. No matter which theater of operations you found yourself in, the enemy was all around on land, sea, and air, ready to deliver a fatal blow and send your ship to the bottom. Fast forward a couple of decades and Navy life was just as hazardous but in a different way, as this Navy training film on the shipboard hazards of low-voltage electricity makes amply clear.

With the suitably scary title “115 Volts: A Deadly Shipmate,” the 1960 film details the many and various ways sailors could meet an untimely end, most of which seemed to circle back to attempts to make shipboard life a little more tolerable. The film centers not on the risks of a ship’s high-voltage installations, but rather the more familiar AC sockets used for appliances and lighting around most ships. The “familiarity breeds contempt” argument rings a touch hollow; given that most of these sailors appear to be in their 20s and 30s and rural electrification in the US was still only partially complete through the 1970s, chances are good that at least some of these sailors came from farms that still used kerosene lamps. But the point stands that plugging an unauthorized appliance into an outlet on a metal ship in a saltwater environment is a recipe for being the subject of a telegram back home.

The film shows just how dangerous mains voltage can be through a series of vignettes, many of which seem contrived but which were probably all too real to sailors in 1960. Many of the scenarios are service-specific, but a few bear keeping in mind around the house. Of particular note is drilling through a bulkhead and into a conduit; we’ve come perilously close to meeting the same end as the hapless Electrician’s Mate in the film doing much the same thing at home. As for up-cycling a discarded electric fan, all we can say is even brand new, that thing looks remarkably deadly.

The fact that they kept killing the same fellow over and over for each of these demonstrations doesn’t detract much from the central message: follow orders and you’ll probably stay alive. In an environment like that, it’s probably not bad advice.

Continue reading “Retrotechtacular: The Deadly Shipmate” →