We are all familiar enough by now with the succession of boards that have come from Raspberry Pi in Cambridge over the years, and when a new one comes out we’ve got a pretty good idea what to expect. The “classic” Pi model B+ form factor has been copied widely by other manufacturers as has their current Compute Module. If you buy the real Raspberry Pi you know you’ll get a solid board with exceptionally good software support.
Every now and then though, they surprise us, with a board that follows a completely different path, which brings us to the one on our bench today. The Compute Module Zero packs the same quad-core RP3 system-on-chip (SoC) and Wi-Fi module as the Pi Zero 2 W with 512 MB of SDRAM onto a tiny 39 mm by 33 mm postage-stamp module. It’s a Pi, but not as you know it, so what is it useful for? Continue reading “Hands On WIth The Raspberry Pi Compute Module Zero”→
A friend of mine and I both have a similar project in mind, the manufacture of custom footwear with our hackerspace’s shiny new multi-material 3D printer. It seems like a match made in heaven, a machine that can seamlessly integrate components made with widely differing materials into a complex three-dimensional structure. As is so often the case though, there are limits to what can be done with the tool in hand, and here I’ve met one of them.
I can’t get a good range of footwear for my significantly oversized feet, and I want a set of extra grippy soles for a particular sporting application. For that the best material is a rubber, yet the types of rubber that are best for the job can unfortunately not be 3D printed. In understanding why that is the case I’ve followed a fascinating path which has taught me stuff about 3D printing that I certainly didn’t know.
Newton strikes back, and I can’t force rubber through this thing.
A friend of mine from way back is a petrochemist, so I asked him about the melting points of various rubbers to see if I could find an appropriate filament His answer, predictably, was that it’s not that simple, because rubbers don’t behave in the same way as the polymers I am used to. With a conventional 3D printer filament, as the polymer is fed into the extruder and heated up, it turns to liquid and flows out of the nozzle to the print. It ‘s then hot enough to fuse with the layer below as it solidifies, which is how our 3D prints retain their shape. This property is where we get the term “plastic” from, which loosely means “Able to be moulded”.
My problem is that rubber doesn’t behave that way. As any casual glance at a motor vehicle will tell you, rubber can be moulded, but it doesn’t neatly liquefy and flow in the way my PLA or PET does. It’s a non-Newtonian fluid, a term which I was familiar with from such things as non-drip paint, tomato ketchup, or oobleck, but had never as an electronic engineer directly encountered in something I am working on. Continue reading “Why Can’t I 3D Print With Rubber?”→
The USB port which first appeared on our computers some time in the mid-1990s has made interfacing peripherals an easy task, save for the occasional upside down connector. But in the days before USB there were a plethora of plugs and sockets for peripherals, often requiring their own expansion card. Among these were mice, and [Robert Smallshire] is here with a potted history of the many incompatible standards which confuse the retrocomputing enthusiast to this day.
The first widely available mice in the 1980s used a quadrature interface, in which the output from mechanical encoders coupled to the mouse ball is fed directly to the computer interface which contains some form of hardware or microcontroller decoder. These were gradually superseded by serial mice that used an RS-232 port, then PS/2 mice, and finally the USB variant you probably use today.
Among those quadrature mice — or bus mice, as early Microsoft marketing referred to them — were an annoying variety of interfaces. Microsoft, Commodore, and Atari mice are similar electrically and have the same 9-pin D connector, yet remain incompatible with each other. The write-up takes a dive into the interface cards, where we find the familiar 8255 I/O port at play. We’d quite like to have heard about the Sun optical mice with their special mouse pad too, but perhaps their omission illustrates the breadth of the bus mouse world.
This piece has certainly broadened our knowledge of quadrature mice, and we used a few of them back in the day. If you only have a USB mouse and your computer expects one of these rarities, don’t worry, there’s an adapter for that.
A friend of mine is producing a series of HOWTO videos for an open source project, and discovered that he needed a better microphone than the one built into his laptop. Upon searching, he was faced with a bewildering array of peripherals aimed at would-be podcasters, influencers, and content creators, many of which appeared to be well-packaged versions of very cheap genericised items such as you can find on AliExpress.
If an experienced electronic engineer finds himself baffled when buying a microphone, what chance does a less-informed member of the public have! It’s time to shed some light on the matter, and to move for the first time in this series from the playback into the recording half of the audio world. Let’s consider the microphone.
Background, History, and Principles
A microphone is simply a device for converting the pressure variations in the air created by sounds, into electrical impulses that can be recorded. They will always be accompanied by some kind of signal conditioning preamplifier, but in this instance we’re considering the physical microphone itself. There are a variety of different types of microphone in use, and after a short look at microphone history and a discussion of what makes a good microphone, we’ll consider a few of them in detail. Continue reading “Know Audio: Microphone Basics”→
Back in the 2000s, Nokia owned the mobile phone space. They had a smartphone OS, even if they didn’t understand app distribution, they had the best cameras, screens, antennas, the lot. They threw it all away with inept management that made late-stage Commodore look competent. Apple and Android came along, and now a Nokia is a rarity. Out of this mess came one good thing, though: the N900 was a Linux-based smartphone that became the go-to hacker mobile for a few years.
First up with this N900 is the long-dead battery. He makes a fake battery with a set of supercapacitors and resistors to simulate the temperature sensor, and is then able to power it from an external PSU. This is refined to a better fake battery using the connector from the original. The device also receives a USB-C port, though due to space constraints, not the PD identifiers, making it (almost) modern.
Because it was a popular hacker device, it’s possible to upgrade the software on an N900. He’s given it U-Boot, and now it boots Linux from an SD card and functions as an online radio device.
For people who build their own model trains there are a range of manufacturers from whom a power bogie containing the motor and drive can be sourced. But as [Le petit train du Berry] shows us in a video, it’s possible to make one yourself and it’s easier than you might think (French language video with truly awful YouTube auto-translation).
At the heart of the design is a coreless motor driving a worm gear at each end that engages with a gear on each axle. The wheelsets and power pickups are off-the-shelf items. The chassis meanwhile is 3D printed, and since this is an ongoing project we see two versions in the video. The V5 model adds a bearing, which its predecessor lacked.
The result is a pretty good power bogie, but it’s not without its faults. The gear ratio used is on the high side in order to save height under a model train body, and in the version without a bearing a hard-wearing filament is required because PLA will wear easily. We’re guessing this isn’t the last we’ll see of this project, so we hope those are addressed in future versions.
We like this project and we think you will too after you’ve watched the video below the break. For more home-made model railway power, how about a linear motor?
There’s an interesting cultural observation to be made as a writer based in Europe, that we like our sans-serif fonts, while our American friends seem to prefer a font with a serif. It’s something that was particularly noticeable in the days of print advertising, and it becomes very obvious when looking at government documents.
