Author: Dan Maloney

3312 Articles

Classic LED Bubble Displays Ride Again

November 17, 2024 by 17 Comments

Hewlett-Packard used to make some pretty cool LED displays, many of which appeared in their iconic pocket calculators back in the 1970s and 1980s. [Upir] tracked down some of these classic bubble displays and used them with a microcontroller. We love the results!

The displays featured here, the HPDL-1414, aren’t quite what would have been found in an HP-35, of course. These displays have 16 segments for reasonably legible approximations of most of the ASCII character set. Also, these aren’t just the displays; rather, a pair of the bubble-topped displays, each with four characters, is mounted to a module that provides a serial interface. [Upir] found these modules online, but despite the HP logo on the PCB silkscreen, it’s not really clear who made them. The documentation was a bit thin, to say the least, but with a little translation help from Google, he figured out the serial parameters and the character encoding. The video below shows him putting these modules through their paces.

Unusually for [upir], who has made a name for himself hacking displays to do things they weren’t designed to do, he stuck with the stock character set baked into this module. We think it would be fun to get one of these modules and hack the firmware to provide alternative character sets or even get a few of the naked displays and build a custom interface. Sounds like a fun rainy-day project.

This reminded us of another HP display project we saw a while back. Or, roll your own displays.

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Homebrew PH Meter Uses Antimony Electrode

November 15, 2024 by 11 Comments

Understanding the nature of pH has bedeviled beginning (and not-so-beginning) chemistry students for nearly as long as chemistry has had students. It all seems so arbitrary, being the base-10 log of the inverse of hydrogen ion concentration and with a measurement range of 0 to 14. Add to that the electrochemical reactions needed to measure pH electronically, and it’s enough to make your head spin.

Difficulties aside, [Markus Bindhammer] decided to tackle the topic and came up with this interesting digital pH meter as a result. Measuring pH electronically is all about the electrode, or rather a pair of electrodes, one of which is a reference electrode. The potential difference between the electrodes when dipped into the solution under test correlates to the pH of the solution. [Markus] created his electrode by drawing molten antimony into a length of borosilicate glass tubing containing a solid copper wire as a terminal. The reference electrode was made from another piece of glass tubing, also with a copper terminal but filled with a saturated solution of copper(II) sulfate and plugged with a wooden skewer soaked in potassium nitrate.

In theory, this electrode system should result in a linear correlation between the pH of the test solution and the potential difference between the electrodes, easily measured with a multimeter. [Marb]’s results were a little different, though, leading him to use a microcontroller to scale the electrode output and display the pH on an OLED.

The relaxing video below shows the build process and more detail on the electrochemistry involved. It might be worth getting your head around this, since liquid metal batteries based on antimony are becoming a thing.

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Desert Island Acetylene From Seashells And Driftwood

November 15, 2024 by 35 Comments

[MacGyver] would be proud of [Hyperspace Pirate]’s rough and ready method of producing acetylene gas from seashells and driftwood.

Acetylene, made by decomposing calcium carbide with water, is a vitally important industrial gas. Not only as a precursor in many chemical processes, but also as the fuel for the famous “blue wrench,” a tool without which auto mechanics working in the Rust Belt would be reduced to tears. To avoid this, [Hyperspace Pirate] started by beachcombing for the raw materials: shells to make calcium oxide and wood to make charcoal. Charcoal is pretty easy; you just cook chunks of wood in a reducing environment to drive off everything but the carbon. Making calcium oxide from the calcium carbonate in the shells isn’t much harder, with ground seashells heated in a propane-fired furnace to release carbon dioxide.

With the raw ingredients in hand, things get a little tricky. Making calcium carbide requires a lot of heat, far more than a simple propane burner can provide. [Hyperspace Pirate] decided to go with an electric arc furnace, to which end he cannibalized a 120 V to 240 V step-up converter for its toroidal transformer, which with a few extra windings provided the needed current to run an arc through carbon electrodes. This generated the needed heat, and then some, as the ceramic firebrick he was using to contain the inferno melted. After rewinding the melted secondary windings on his makeshift transformer and switching to a stainless steel crucible, he was able to make enough calcium carbide to generate an impressive amount of acetylene. The video below documents the process and the sooty results, as well as details a little of the excitement that metal acetylides offer.

For more about acetylene and its many uses, [This Old Tony] has you covered.

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Retro Calculator Build Proves The Space Age Isn’t What It Used To Be

November 14, 2024 by 20 Comments

The common wisdom these days is that even if we wanted to get back to the Moon the way we did in the 1960s, we’d never be able to do it. Most of the blame for that usually falls on the loss of institutional knowledge thanks to skilled minds and hands that have been stilled by the passage of time, but the real kicker would be finding replacements for all the parts that we used back then that just aren’t made anymore. A similar problem exists for those seeking to recreate the circuits that graced the pages of the many magazines that catered to electronics hobbyists back in the day.

Take this “Space Age Decimal Computer” reproduction that [Bob Alexander] undertook. Smitten with the circuit after seeing our story about a 1966 article detailing its construction, he decided to roll one of his own. That proved to be far harder than he thought it would be. The original circuit, really little more than an adding machine using a rotary telephone dial as an input device, used neon lamp ring buffers for counting, The trouble is, while NE-2 neon lamps are still made, they aren’t made very precisely. That makes it difficult to build a working ring buffer, which relies on precise on and off voltages. That was even a problem back then; the author suggested buying 100 lamps and carefully characterizing them after aging them in to get the 60 lamps needed.

In the end, [Bob] settled for modifying the circuit while making the build look as close as possible to the original. He managed to track down the exact model of enclosure used in the original. The front panel is populated with a rotary dial just like the original, and the same neon lamps are used too, but as indicators rather than in ring buffers. Behind the scenes, [Bob] relied on 7400-series counters and decoders to make it all work — kudos for sticking with 1970s tech and not taking the easy way out with an Arduino.

The video below goes into more detail on the build and the somewhat kludgy operation of the machine, with a few excellent [Tom Lehrer] references and a nice Cybertruck dunk to boot.

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Bluetooth Dongle Gives Up Its Secrets With Quick Snooping Hack

November 14, 2024 by 5 Comments

There’s a lot going on in our wireless world, and the number of packets whizzing back and forth between our devices is staggering. All this information can be a rich vein to mine for IoT hackers, but how do you zero in on the information that matters? That depends, of course, but if your application involves Bluetooth, you might be able to snoop in on the conversation relatively easily.

By way of explanation, we turn to [Mark Hughes] and his Boondock Echo, a device we’ve featured in these pages before. [Mark] needed to know how long the Echo would operate when powered by a battery bank, as well as specifics about the power draw over time. He had one of those Fnirsi USB power meter dongles, the kind that talks to a smartphone app over Bluetooth. To tap into the conversation, he enabled Host Control Interface logging on his phone and let the dongle and the app talk for a bit. The captured log file was then filtered through WireShark, leaving behind a list of all the Bluetooth packets to and from the dongle’s address.

That’s when the fun began. Using a little wetware pattern recognition, [Mark] was able to figure out the basic structure of each frame. Knowing the voltage range of USB power delivery helped him find the bytes representing voltage and current, which allowed him to throw together a Python program to talk to the dongle in real-time and get the critical numbers.

It’s not likely that all BLE-connected devices will be as amenable to reverse engineering as this dongle was, but this is still a great technique to keep in mind. We’ve got a couple of applications for this in mind already, in fact.

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Retrotechtacular: The TV Bombs Of WWII

November 14, 2024 by 41 Comments

Anyone who was around for the various wars and conflicts of the early 2000s probably recalls the video clips showing guided bombs finding their targets. The black-and-white clips came from TV cameras mounted in the nose of the bomb, and were used by bombardiers to visually guide the warhead to the target — often providing for a level of precision amounting to a choice of “this window or that window?” It was scary stuff, especially when you thought about what was on the other side of the window.

Surprisingly, television-guide munitions aren’t exactly new, as this video on TV-guided glide bombs in WWII indicates. According to [WWII US Bombers], research on TV guidance by the US Army Air Force started in 1943, and consisted of a plywood airframe built around a standard 2000-pound class gravity bomb. The airframe had stubby wings for lift and steerable rudders and elevators for pitch and yaw control. Underneath the warhead was a boxy fairing containing a television camera based on an iconoscope or image orthicon, while all the radio gear rode behind the warhead in the empennage. A B-17 bomber could carry two GB-4s on external hardpoints, with a bulky TV receiver provided for the bombardier to watch the bomb’s terminal glide and make fine adjustments with a joystick.

In testing, the GB-4 performed remarkably well. In an era when a good bombardier was expected to drop a bomb in a circle with a radius of about 1,200′ (365 meters) from the aim point, GB-4 operators were hitting within 200′ (60 meters). With results like that, the USAAF had high hopes for the GB-4, and ordered it into production. Sadly, though, the testing results were not replicated in combat. The USAAF’s 388th Bomber Group dropped a total of six GB-4s against four targets in the European Theater in 1944 with terrible results. The main problem reported was not being able to see the target due to reception problems, leaving the bombardiers to fly blind. In other cases, the bomb’s camera returned a picture but the contrast in the picture was so poor that steering the weapon to the target was impossible. On one unfortunate attack on a steel factory in Duren, Germany, the only building with enough contrast to serve as an aiming point was a church six miles from the target.

The GB-4’s battlefield service was short and inglorious, with most of the 1,200 packages delivered never being used. TV-guided bombs would have to wait for another war, and ironically it would be the postwar boom in consumer electronics and the explosion of TV into popular culture would move the technology along enough to make it possible.

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Landscape Motif Makes This E-Ink Weather Display Easy To Understand

November 13, 2024 by 11 Comments

True weather geeks will disagree, but there might be a better way to know how to dress for the day than divining what the weather will likely be from the current readings for temperature, pressure, humidity, and wind. Sure, the data will give you a good idea of where the weather is heading, but perhaps a quick visual summary such as the one offered by this pictorial landscape weather display is a better way to get out the door in the morning.

While many consumer weather stations incorporate some kind of graphical forecast for quick reference, [lds133] took a slightly different approach to forecasting. A cartoon landscape represents the day ahead, with various elements representing the coming weather scrolling across the display as time progresses. Trees are used to indicate wind direction and speed, with palm trees indicating south wind and pine trees winds from the north, and the taller the trees, the stronger the wind. The forest floor rises and falls with the expected temperature, the sun and moon appear at the proper time to indicate sunrise and sunset, and cloud icons are added when needed to show the degree of cloud cover. And because into each life a little rain must fall, animations show when you can expect rain or snow.

As for the electronics, if you think this would be a perfect application for an E-ink module, [lds133] agrees. The 296×128 pixel Waveshare display is the perfect aspect ratio for the job and provides nice, crisp icons. The display is updated every 15 minutes from the OpenWeather API by a Python program running on an ESP32 behind the scenes.

We’ve seen similar graphical forecast displays before, but we get it if that’s not your thing. Perhaps a more data-driven weather forecast will suit you better?