Review: Testdriving LibrePCB Shows That It’s Growing Up Fast

There are a host of PCB CAD tools at the disposal of the electronic designer from entry-level to multi-thousand-dollar workstation software. It’s a field in which most of the players are commercial, and for the open-source devotee there have traditionally been only two choices. Both KiCad and gEDA are venerable packages with legions of devoted fans, but it is fair to say that they both present a steep learning curve for newcomers. There is however another contender in the world of open-source PCB CAD, in the form of the up-and-coming LibrePCB.

This GPL-licensed package has only been in development for a few years. LibrePCB brought out its first official release a little over a year ago, and now stands at version 0.1.3 with builds for GNU/Linux, Windows, MacOS, and FreeBSD. It’s time to download it and run it through its paces, to see whether it’s ready to serve its purpose.

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A Kill Cord To End Laptop Skulduggery

In our community it is common for ancient laptops to be used way beyond their usual service life, held together by stickers and lovingly upgraded to their maximum capabilities. We hope it’s unusual for such a venerable machine to be stolen, but it seems that grab-and-run thefts are very much a thing for owners of much shinier hardware. [Michael Altfield] has a solution to this problem, in the form of a kill cord that when broken by the crook making off with the loot, triggers a set of scripts that can wipe the device or otherwise make it useless.

Hardware-wise it’s simple enough, a USB magnetic breakaway adapter and a USB extension cable to a drive clipped to the laptop owner’s belt. On the software side it’s as straightforward as a udev rule to launch the disaster script of your choice. Perhaps you could link it to something like a glitter bomb and fart spray. But we can’t help worrying that it might be too easy to get up and accidentally detach yourself from the laptop, making it deploy whatever anti-theft measure you’d installed in error. If this goes some way to reducing theft though, it has to be worth a second look.

Thanks [bluewraith] for the tip.

A Strange Display Gives Up Its Secrets

Providing a display for a project in 2020 is something of a done deal. Standard interfaces and off-the-shelf libraries for easily available and cheap modules mean that the hardest choice you’ll have to make about a display will probably relate to its colour. Three decades ago though this was not such a straightforward matter though, and having a display that was in any way complex would in varying proportion take a significant proportion of your processing time , and cost a fortune. [AnubisTTP] has an unusual display from that era, a four-digit LED dot matrix module, and the take of its reverse engineering makes for a fascinating read.

The LITEF 104267 was made in 1986, and is a hybrid circuit in a metal can with four clear windows , one positioned over each LED matrix. Inside are seven un-encapsulated chips alongside the LED matrices on a golf plated hybrid substrate. The chips themselves are not of a particularly high-density process, so some high-resolution photography was able to provide a good guess at their purpose. A set of shift registers drive the columns through buffers, while the rows are brought out to a set of parallel lines. Thus each column can be illuminated sequentially with data presented on the rows. It’s something that would have saved a designer of the day a few extra 74-series chips, though we are guessing at some significant cost.

This display may seem antiquated to us today, but it wasn’t the only option for 1980s designers. There’s one display driver from back then that’s very much still with us today.

Car Alternators Make Great Electric Motors; Here’s How

The humble automotive alternator hides an interesting secret. Known as the part that converts power from internal combustion into the electricity needed to run everything else, they can also themselves be used as an electric motor.

The schematic of a simple automotive alternator, from US patent 3329841A filed in 1963 for Robert Bosch GmbH .
The schematic of a simple automotive alternator, from US patent 3329841A filed in 1963 for Robert Bosch GmbH.

These devices almost always take the form of a 3-phase alternator with the magnetic component supplied by an electromagnet on the rotor, and come with a rectifier and regulator pack to convert the higher AC voltage to 12V for the car electrical systems. Internally they have three connections to the stator coils which appear to be universally wired in a delta configuration, and a pair of connections to a set of brushes supplying the rotor coils through a set of slip rings. They have a surprisingly high capacity, and estimates put their capabilities as motors in the several horsepower. Best of all they are readily available second-hand and also surprisingly cheap, the Ford Focus unit shown here came from an eBay car breaker and cost only £15 (about $20).

We already hear you shouting “Why?!” at your magical internet device as you read this. Let’s jump into that.

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One ESP8266, One Battery, One Year… And Counting.

There are times when a sensor is required that does its job without the need for human attention over a long period, and for those applications a minimal power drain is a must. [Dave Davenport] had an EPS8266-based moisture sensor, and became disappointed in having to replace its AA batteries every few months. With an 18650 Li-ion cell and a bunch of power-saving tricks that time has been extended so far to over a year and still going, so he’s written a blog post detailing how he did it.

Some of his techniques such as turning off the sensor or using a better LDO regulator than the stock Wemos one are straightforward. Others though are unexpected, such as using the memory associated with the on-board RTC to store the WiFi connection info and channel number during sleep. The normal ESP8266 connection sequence involves a network scan, by hanging onto what it found last time the extra time and thus power expended by it can be avoided. Similarly switching from a DHCP lease to a fixed IP address cuts the time the device waits for a lease and thus the time it has to stay awake.

We might not all have ESP8266 moisture sensors to build, but we’re many of us on a quest to sip less power in our projects. Let us help you with a previous sojourn into that arena.

ESP8266 image: connorgoodwolf [CC BY-SA 4.0].

A Vintage Phone In 2020

When we make a telephone call in 2020 it is most likely to be made using a smartphone over a cellular or IP-based connection rather than a traditional instrument on a pair of copper wires to an exchange. As we move inexorably towards a wireless world in which the telephone line serves only as a vehicle for broadband Internet, it’s easy to forget the last hundred years or more of telephone technology that led up to the present.

The iconic British telephone of the 1960s and 1970s, the GPO model 746. Mine is from 1971.
The iconic British telephone of the 1960s and 1970s, the GPO model 746. Mine is from 1971. (That isn’t my phone number)

In a manner of speaking though, your telephone wall socket hasn’t forgotten. If you like old phones, you can still have one, and picture yourself in a 1950s movie as you twirl the handset cord round your finger while you speak. Continue reading “A Vintage Phone In 2020”

Awakening A Dragon From Its Slumber

For all the retrocomputing fun and games we encounter in our community, there are a few classic microcomputers that rarely receive any attention. Usually this is because they didn’t sell well and not many have survived, or were simply underwhelming machines that haven’t gathered a huge following today. One that arguably falls within both camps is the Dragon 32, a machine best known in those pre-Raspberry Pi days for being the only home computer manufactured in Wales, and for being nearly compatible with the Tandy Color Computer due to both machines’ designs coming from the same Motorola data sheet. Repeat restorer of retrocomputers, [Drygol], has given a Dragon 32 the full restoration and upgrade treatment, offering us a rare chance to take a look at this computer.

The Dragon arrived with a pile of contemporary books and software, but no power supply. A significant modification was made to the internal PSU board then to allow it to work with an Amiga unit, and the black-on-green Dragon text came up on the TV screen. Recapping and a replacement for a faulty op-amp fixed poor video quality, then it was time for a 64K memory upgrade with some neatly done bodge-wiring. Finally there’s a repair to the very period-looking analogue joystick, and a home-made interface for the more common Atari/Amiga style sticks.

The Dragon may be only a footnote in the history of 8-bit home computing, but with its good expandability and decent quality keyboard it perhaps deserved to reach more homes than it did. This appears to be the first time a Dragon has featured here, though its Tandy CoCo cousin has made it into a few stories.