Most one-handed keyboards rely on modifier keys or chording (pressing multiple keys in patterns) to stretch the functionality of a single hand’s worth of buttons. [Dylan Turner]’s PS-OHK takes an entirely different approach, instead putting 75 individual keys within reach of a single hand, with a layout designed to be practical as well as easy to get used to.
We can’t help but notice Backspace isn’t obvious in the prototype, but it’s also a work in progress.
The main use case of the PS-OHK is for one hand to comfortably rest at the keyboard while the other hand manipulates a mouse in equal comfort. There is a full complement of familiar special keys (Home, End, Insert, Delete, PgUp, PgDn) as well as function keys F1 to F12 which helps keep things familiar.
As for the rest of the layout, we like the way that [Dylan] clearly aimed to maintain some of the spatial relationship of “landmark” keys such as ESC, which is positioned at the top-left corner of its group. Similarly, arrow keys are grouped together in the expected pattern.
One-handed keyboards usually rely on modifier keys or multi-key chording and it’s interesting to see work put into a different approach that doesn’t require memorizing strange layouts or input patterns.
Want to make your own? The GitHub repository has everything you need. Accommodating the 75 physical keys requires a large PCB, but it’s a fairly straightforward shape and doesn’t have any oddball manufacturing requirements, which means getting it made should be a snap.
High-tech movie guides on CD-ROM; clearly the future had arrived in 1994.
In the innocent days of the early 90s the future of personal computing still seemed to be wide open, with pundits making various statements regarding tis potential trajectories. To many, the internet and especially the World Wide Web didn’t seem to be of any major significance, as it didn’t have the reach or bandwidth for the Hot New Thingtm in the world of PCs: multimedia. Enter the CD-ROM, which since its introduction in 1985 had brought the tantalizing feature of seemingly near-infinite storage within reach, and became cheap enough for many in the early 90s. In a recent article by [Harry McCracken] he reflects on this era, and how before long it became clear that it was merely a bubble.
Of course, there was a lot of good in CD-ROMs, especially when considering having access to something like Encarta before Wikipedia and broadband internet was a thing. It also enabled software titles to be distributed without the restrictions of floppy disks. We fondly remember installing Windows 95 (without Internet Explorer) off 13 1.44 MB floppies, followed by a few buckets of Microsoft Office floppies. All pray to the computer gods for no sudden unreadable floppy.
Inevitably, there was a lot of shovelware on CD-ROMs, and after the usefulness of getting free AOL floppies (which you could rewrite), the read-only CD-ROMs you got in every magazine and spam mailing were a big disappointment. Although CD-ROMs and DVDs still serve a purpose today, it’s clear that along with the collapse of the Internet Bubble of the late 90s, early 2000s, optical media has found a much happier place. It’s still hard to beat the sheer value of using CD-R(W)s and DVD-/+R(W)s (and BD-Rs) for offline backups, even if for games and multimedia they do not appear to be relevant any more.
There is perhaps no more important time to have a business card than when you’re in college, especially near the end when you’re applying for internships and such. And it’s vital that you stand out from the crowd somehow. To that end, Electrical & Computer Engineer [Ryan Chan] designed a tidy card that plays tic-tac-toe.
Instead of X and O, the players are indicated by blue and red LEDs. Rather than having a button at every position, there is one big control button that gets pressed repeatedly until your LED is in the desired position, and then you press and hold to set it and switch control to the other player. In addition to two-player mode, the recipient of your card can also play alone against the ATMega.
The brains of this operation is an ATMega328P-AU with the Arduino UNO bootloader for ease of programming. Schematic and code are available if you want to make your own, but we suggest implementing some type of changes to make it your own. Speaking of, [Ryan] has several next steps in mind, including charlieplexing the LEDs, using either USB-C or a coin cell for power, upgrading the AI, and replacing the control button with a capacitive pad or two. Be sure to check it out in action in the two videos after the break.
Displays are crucial to modern life; they are literally everywhere. But modern flat-panel LCDs and cheap 7-segment LED displays are, well, a bit boring. When we hackers want to display the progress of time, we want something more interesting, hence the plethora of projects using Nixie tubes and various incantations of edge-lit segmented units. Here is [upir] with their take on the simple edge-lit acrylic 7-segment design, with a great video explanation of all the steps involved.
Engraving the acrylic sheets by hand using 3D printed stencils
The idea behind this concept is not new. Older displays of this type used tiny tungsten filament bulbs and complex light paths to direct light to the front of the display. The modern version, however, uses edge-lit panels with a grid of small LEDs beneath each segment, which are concealed within a casing. This design relies on the principle of total internal reflection, created by the contrast in refractive indices of acrylic and air. Light entering the panel from below at an angle greater than 42 degrees from normal is entirely reflected inside the panel. Fortunately, tiny LEDs have a wide dispersion angle, so if they are positioned close enough to the edge, they can guide sufficient light into the panel. Once this setup is in place, the surface can be etched or engraved using a CNC machine or a laser cutter. A rough surface texture is vital for this process, as it disrupts some of the light paths, scattering and directing some of it sideways to the viewer. Finally, to create your display, design enough parallel-stacked sheets for each segment of the display—seven in this case, but you could add more, such as an eighth for a decimal point.
How you arrange your lighting is up to you, but [upir] uses an off-the-shelf ESP32-S3 addressable LED array. This design has a few shortcomings, but it is a great start—if a little overkill for a single digit! Using some straightforward Arduino code, one display row is set to white to guide light into a single-segment sheet. To form a complete digital, you illuminate the appropriate combination of sheets. To engrave the sheets, [upir] wanted to use a laser cutter but was put off by the cost. A CNC 3018 was considered, but the choice was bewildering, so they just went with a hand-engraving pick, using a couple of 3D printed stencils as a guide. A sheet holder and light masking arrangement were created in Fusion 360, which was extended into a box to enclose the LED array, which could then be 3D printed.
[Luizão] wanted to create some hardware to honour the memory of the technology used to put man on the moon and chose the literal core of the project, that of the hardware used to store the software that provided the guidance. We’re talking about the magnetic core rope memory used in the Colossus and Luminary guidance computers. [Luizão] didn’t go totally all out and make a direct copy but instead produced a scaled-down but supersized demo board with just eight cores, each with twelve addressable lines, producing a memory with 96 bits.
The components chosen are all big honking through-hole parts, reminiscent of those available at the time, nicely laid out in an educational context. You could easily show someone how to re-code the memory with only a screwdriver to hand; no microscope is required for this memory. The board was designed in EasyEDA, and is about as simple as possible. Being an AC system, this operates in a continuous wave fashion rather than a pulsed operation mode, as a practical memory would. A clock input drives a large buffer transistor, which pushes current through one of the address wires via a 12-way rotary switch. The cores then act as transformers. If the address wire passes through the core, the signal is passed to the secondary coil, which feeds a simple rectifying amplifier and lights the corresponding LED. Eight such circuits operate in parallel, one per bit. Extending this would be easy.
[Ken Shirriff] likes to take chips apart and this time his target is an NFC chip used in Montreal transit system tickets. As you might expect, the tickets are tiny, cheap, and don’t have any batteries. So how does it work?
The chip itself is tiny at 570 µm × 485 µm. [Ken] compares it to a grain of salt. The ticket has a thin plastic core with a comparatively giant antenna onboard.
It is funny how sometimes things you think are bad turn out to be good in retrospect. Like many of us, when I was a kid, I was fascinated by science of all kinds. As I got older, I focused a bit more, but that would come later. Living in a small town, there weren’t many recent science and technology books, so you tended to read through the same ones over and over. One day, my library got a copy of the relatively recent book “The Amateur Scientist,” which was a collection of [C. L. Stong’s] Scientific American columns of the same name. [Stong] was an electrical engineer with wide interests, and those columns were amazing. The book only had a snapshot of projects, but they were awesome. The magazine, of course, had even more projects, most of which were outside my budget and even more of them outside my skill set at the time.
If you clicked on the links, you probably went down a very deep rabbit hole, so… welcome back. The book was published in 1960, but the projects were mostly from the 1950s. The 57 projects ranged from building a telescope — the original topic of the column before [Stong] took it over — to using a bathtub to study aerodynamics of model airplanes.
X-Rays
[Harry’s] first radiograph. Not bad!However, there were two projects that fascinated me and — lucky for me — I never got even close to completing. One was for building an X-ray machine. An amateur named [Harry Simmons] had described his setup complaining that in 23 years he’d never met anyone else who had X-rays as a hobby. Oddly, in those days, it wasn’t a problem that the magazine published his home address.
You needed a few items. An Oudin coil, sort of like a Tesla coil in an autotransformer configuration, generated the necessary high voltage. In fact, it was the Ouidn coil that started the whole thing. [Harry] was using it to power a UV light to test minerals for flourescence. Out of idle curiosity, he replaced the UV bulb with an 01 radio tube. These old tubes had a magnesium coating — a getter — that absorbs stray gas left inside the tube.
