A new display wedged into a car-based fridge

New Brains Save 12 V Fridge From The Scrap Heap

March 14, 2024 by 17 Comments

Recently [nibbler]’s Evakool 55L vehicle fridge started to act strangely, reporting crazy temperature errors and had no chance of regulating. The determination was that the NTC thermistor was toast, and rather than trying to extricate and replace this part, it was a lot easier to add a new one at a suitable location

Bog-standard fridge internals

A straight swap would have been boring, so this was a perfect excuse for an overboard hack. Reverse engineering the controller wouldn’t be easy, as the data wasn’t available, as is often the case for many products of this nature.

While doing a brain transplant, the hacker way, we can go overboard and add the basics of an IoT control and monitoring system. To that end, [nibbler] learned as much as possible about the off-the-shelf ZH25G compressor and the associated compressor control board. The aim was to junk the original user interface/control board and replace that with a Raspberry Pi Pico W running CircuitPython.

For the display, they used one of the ubiquitous SH1106 monochrome OLED units that can be had for less than the cost of a McDonald’s cheeseburger at the usual purveyors of cheap Chinese electronics.  A brief distraction was trying to use a DS18B20 waterproof thermometer probe, which they discovered didn’t function, so they reverted to tried and trusted tech — a simple NTC thermistor.

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Retrotechtacular: Air Mail For The Birds

March 14, 2024 by 9 Comments

Today, if you want to send a message to a distant location, you’ll probably send an e-mail or a text message. But it hasn’t always been that easy. Military commanders, in particular, have always needed ways to send messages and were early adopters of radio and, prior to that, schemes like semaphores, drums, horns, Aldis lamps, and even barrels of water to communicate over distances.

One of the most reliable ways to pass messages, even during the last world war, was by carrier pigeon.  Since the U.S. Army Signal Corps handled anything that included messages, it makes sense that the War Department issued TM 11-410 about how to use and care for pigeons. Think of it as the network operations guide of 1945. The practice, though, is much older. There is evidence that the Persians used pigeons in the 6th century BC, and Julius Caesar’s army also used the system.

You wouldn’t imagine that drawing an assignment in the Signal Corps might involve learning about breeding pigeons, training them, and providing them with medical attention, but that’s what some Signal Corps personnel did. The Army started experimenting with pigeons in 1878, but the Navy was the main user of the birds until World War I, when the U.S. Pigeon Intelligence Service was formed. In World War II, they saw use in situations where radio silence was important, like the D-Day invasion.

The Navy also disbanded its earlier Pigeon Messenger Service. It then returned to avian communications during the World Wars, using them to allow aviators to send messages back to base without radio traffic. The Navy had its own version of the pigeon manual.

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Dev Board Watch Takes Path Of Least Resistance

March 14, 2024 by 9 Comments

Building your own watch or clock is kind of a maker’s rite of passage. Once upon a time, if you went with a wrist watch, you’d typically work on producing your own compact PCB with everything crammed into a typical watch form factor, maybe relying on a simple binary output for compactness and simplicity. Times have changed, however, and [Arnov]’s design is altogether different in its construction.

The build relies on a XIAO ESP32-C3 microcontroller board as the brains of the operation. It’s paired with the XIAO expansion board. It’s designed as a carrier for the ESP32-C3, giving it a bunch of IO that’s accessible over readily-accessible connectors. It also features a display, a real-time clock, and a battery — pretty much the three main things you’d need to add to an ESP32 to turn it into a watch.

Thus, with the electronics pretty much done, it was simply up to [Arnov] to turn the device into a watch. He achieved this by screwing the frame and strap of an old Casio watch to a 3D printed carrier for the XIAO expansion board. With that done, it was simply a matter of writing the code to show the time from the RTC on the display. There’s no connectivity features, no smart stuff going on — just the time and date for your perusal.

Some might decry the project for simply slapping a watch band on a devboard. Or, you could look at how this indicates just how fast and easy development can be these days. Once upon a time, you could spend weeks trying to find a cheap display and then further weeks trying to get it working with your microcontroller. Now you can spend $20, get the parts in a few days, and get your project blasting along minutes later.

If you’ve done an altogether more ornate watch build of your own, we’d love to see that, too. Show us on the tipsline!

Lithium-Ion Batteries Power Your Devboards Easily

March 14, 2024 by 25 Comments

Last summer, I was hanging out with a friend from Netherlands for a week, and in the middle of that week, we decided to go on a 20 km bike trip to a nearby beach. Problem? We wanted to chat throughout the trip, but the wind noise was loud, and screaming at each other while cycling wouldn’t have been fun. I had some walkie-talkie software in mind, but only a single battery-powered Pi in my possession. So, I went into my workshop room, and half an hour later, walked out with a Pi Zero wrapped in a few cables.

I wish I could tell you that it worked out wonders. The Zero didn’t have enough CPU power, I only had single-core ones spare, and the software I had in mind would start to badly stutter every time we tried to run it in bidirectional mode. But the battery power solution was fantastic. If you need your hack to go mobile, read on.

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High-Voltage Fun With An Inexpensive Power Supply

March 14, 2024 by 25 Comments

It used to be that nearly every home had at least one decent high-voltage power supply. Of course, it was dedicated to accelerating electrons and slamming them into phosphors so we could bathe ourselves in X-rays (not really) while watching Howdy Doody. These days the trusty tube has been replaced with LEDs and liquid crystals, which is a shame because there’s so much fun to be had with tens of thousands of volts at your disposal.

That’s the impetus behind this inexpensive high-voltage power supply by [Sebastian] over at Baltic Labs. The heavy lifting for this build is done by a commercially available power supply for a 50-watt CO2 laser tube, manufactured — or at least branded — by VEVOR, a company that seems intent on becoming the “Harbor Freight of everything.” It’s a bold choice given the brand’s somewhat questionable reputation for quality, but the build quality on the supply seems decent, at least from the outside. [Sebastian] mounted the supply inside a rack-mount case, as one does, and provided some basic controls, including the obligatory scary-looking toggle switch with safety cover. A pair of ammeters show current and voltage, the latter with the help of a high-voltage resistor rated at 1 gigaohm (!). The high-voltage feedthrough on the front panel is a little dodgy — a simple rubber grommet — but along with the insulation on the high-voltage output lead, it seems to be enough.

The power supply’s 30 kV output is plenty for [Sebastian]’s current needs, which from the video below appear to mainly include spark gap experiments. He does mention that 50 kV commercial supplies are available too, but it would be tough to do that for the $150 or so he spent on this one. There are other ways to go, of course — [Niklas] over at Advanced Tinkering recently shared his design for a more scratch-built high-voltage supply that’s pretty cool too. Whatever you do, though, be careful; we’ve been bitten by a 50 kV flyback supply before and it’s no joke.

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A Compact SCARA Arm Plotter

March 14, 2024 by 4 Comments

If you’re unfamiliar with SCARA robots, the acronym stands for Selective Compliance Assembly Robot Arm. This refers to the fact that the arms are rigid in the Z axis but somewhat compliant in the X and Y axes, and that they’re often used for assembly tasks. In any case, you can spend a great deal of money equipping your factory with these robots, or you can build your own for the fun of it. If you’re not endowed with a seven-figure investment for opening a production plant, consider exploring [tuenhidiy’s] project instead.

The build enlists an Arduino Mega as the brains of the operation. It’s paired with a RAMPS controller for running a pair of NEMA 17 stepper motors that actually move the arm in the X-Y plane. Additionally, a tray eject mechanism from a CD/DVD drive is enlisted to act as the Z axis. The frame is assembled from PVC plumbing components and a small amount of aluminium T-slot profile.

The resulting arm isn’t fast in the video we see of the build, but it works as a basic plotter without too much complaint. The benefit of the Z-axis in this case is obvious, as it allows the pen to be lifted off the page where necessary.

We’ve seen plenty of good plotter designs around these parts before, too. Video after the break.

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Two ICL PERQ 1 workstation computers, Department of Computer Science, North Machine Hall, James Clerk Maxwell Building, University of Edinburgh. (Credit: J. Gordon Hughes)

The Flex Computer System: UK’s Forgotten Capability Computer Architecture

March 13, 2024 by 20 Comments

During the 1970s many different computer architectures were being developed, many of them focused on making computer systems easier and more effective to use. The Flex Machine developed at the UK Ministry of Defence’s Royal Signals and Radar Establishment (RSRE) was one of them, falling in the category of Capability Architectures. These architectures required hardware with programmable microcode, which required either custom hardware, or computer systems like the Xerox Alto-inspired ICL PERQ (pictured). What’s interesting about Flex is that it didn’t just remain in the 1980s as a quaint footnote, but as detailed by [Martin C. Atkins] – who worked on the system – evolved into the Ten15 system, which later got renamed to TenDRA.

Capability architectures have a long history – including the Intel iAPX 432 and more recent implementations – but they all have in common is that they effectively implement an object-based memory architecture, rather than the low-level, flat memory space that we usually see with computer systems. These object-based capabilities, as they were termed, provides a level of memory protection and security that would be hard to implement otherwise. The book Capability-Based Computer Systems by [Henry M. Levy] forms a good introduction here.

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