Manual Supports For 3D Printing

April 21, 2024 by 11 Comments

[MakerSpace] wanted to 3D print an RFID card holder. On one side is a slot for a card and on the other side has recesses for the RFID antenna. They used these to control access to machines and were milling them out using a CNC machine. Since there were no flat surfaces, he had to turn on supports in the slicer, right? No. He does use supports, but not in the way you might imagine.

Inspired by creating cast iron using sand casting, he decided to first 3D print a reusable “core” using PETG. This core will support future prints that use PLA. When printing the actual item, the printer lays down the first few layers and pauses. This allows you to stick the core in and resume the print. After the print completes, you can remove the core, and the results look great, as you can see in the video below.

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Radio Frequency Burns, Flying A Kite, And You

April 21, 2024 by 20 Comments

Most hams can tell you that it’s possible to get a nasty RF burn if you accidentally touch an antenna while it’s transmitting. However, you can also cop a nasty surprise on the receiving end if you’re not careful, as explained in a video from [Grants Pass TV Repair].

It’s hard to see in a still image, but the RF burns from the kite antenna actually generate a little puff of smoke on contact.

An experiment was used to demonstrate this fact involving a kite and a local AM broadcaster. A simple calculation revealed that an antenna 368 feet and 6 inches long would be resonant with the KAJO Radio signal at 1.270 MHz. At half the signal’s wavelength, an antenna that long would capture plenty of energy from the nearby broadcast antenna.

Enter the kite, which served as a skyhook to loft an antenna that long. With the wire in the air picking up a strong signal from the AM radio tower, it was possible to get a noticable RF burn simply by touching the end of the antenna.

The video explains that this is a risky experiment, but not only because of the risk of RF burn itself. It’s also easy to accidentally get a kite tangled in power lines, or to see it struck by lightning, both of which would create far greater injuries than the mild RF burn seen in the video. In any case, even if you know what you’re doing, you have to be careful when you’re going out of your way to do something dangerous in the first place.

AM radio towers aren’t to be messed with; they’ve got big power flowing. Video after the break.

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From Z80 To EZ80: Porting 8-bit Sonic 2 To The TI-84+ CE

April 21, 2024 by 4 Comments

An unwritten rule is that if two systems runs even roughly the same CPU, you are obligated to port software between them, or at least give it a fair shake. This led [grubbycoder] down the path of porting Sonic 2 for the Sega Master System (to the eZ80-based Ti 84+ CE. Selecting this particular graphing calculator came down to the raw specs matching up the best, as although the eZ80 in the Ti 84+ runs at 48 MHz, it’s got wait states that cripple its actual performance. Since the calculator also lacks the Video Display Processor (VDP) and a few other bits of hardware, those extra cycles are crucial to compensate.

Sonic 2 on the Ti 84+ CE, courtesy of [grubbycoder]
Sonic 2 on the Ti 84+ CE, courtesy of [grubbycoder]
Getting the disassembled version of the game was easy enough, as the [Sonic Retro] team has already done the heavy lifting there. The only snag there was that this was in WLA-DX assembler format, which is great if you just want to create a ROM for a Z80 system, but for the eZ80 you need a different assembler. Here SPASM-ng came to the rescue, as it targets both Z80 and eZ80-based Ti calculators in particular.

With those ducks aligned, the next task was to address the hardware differences. The calculator has no sound, so those routines had to go, and the color palettes of the Master System had to be mapped to that of the calculator. Since it’s a calculator, there were plenty of buttons for input, but ROM banking – which isn’t a thing on the Ti calculator – and the background and sprite rendering posed some issues. With that sorted, anyone with this calculator can now rejoice at having something better to play on their calculators than Snake in between heavy linear algebra sessions.

An Open-Source Gaming Mouse

April 21, 2024 by 10 Comments

It’s a shame, that peripherals sold as of higher performance for gaming so often deliver little but aggressive styling. [Wareya] became frustrated with the fragile switches on his choice of gaming mouse, so decided to design his own. In the video that he’s placed below the break, he takes us through all the many choices and pitfalls inherent to these devices

After quite a few iterations he arrived upon a design featuring an RP2040 and an optical sensor easily found in relatively inexpensive mice. The whole design is open source and can be found in a GitHub repository, but for us perhaps the most interesting part of the explanation lies in the use of a three-contact switch, and how the third contact is used to aid in debouncing. In an application in which latency is of paramount importance this is a key design feature of a gaming mouse.

Perhaps it’s a mark of how good computer mice are in general that we see so relatively few projects building them from scratch rather than modifying exiting ones, but despite that a few have made it to these pages. Continue reading “An Open-Source Gaming Mouse” →

The experimental setup – a Commodore 64 is connected to a monitor through a composite video to HDMI converter, with the code cartridge inserted into the expansion port.

Trolling IBM’s Quantum Processor Advantage With A Commodore 64

April 20, 2024 by 8 Comments
The memory map ofthe implementation, as set within the address space of the Commodore 64 - about 15kB of the accessible 64kB RAM is used. 8kB of this is reserved for code, although most of this is unused. Each of the two bitstrings for each Pauli string is stored separately (labeled as Pauli String X/Z) for more efficient addressing.
The memory map of
the implementation, as set within the address space of the Commodore 64 – about 15kB of the accessible 64kB RAM is used.

There’s been a lot of fuss about the ‘quantum advantage’ that would arise from the use of quantum processors and quantum systems in general. Yet in this high-noise, high-uncertainty era of quantum computing it seems fair to say that the advantage part is a bit of a stretch. Most recently an anonymous paper (PDF, starts at page 199) takes IBM’s claims with its 127-bit Eagle quantum processor to its ludicrous conclusion by running the same Trotterized Ising model on the ~1 MHz MOS 6510 processor in a Commodore 64. (Worth noting: this paper was submitted to Sigbovik, the conference of the Association for Computational Heresy.)

We previously covered the same claims by IBM already getting walloped by another group of researchers (Tindall et al., 2024) using a tensor network on a classical computer. The anonymous submitter of the Sigbovik paper based their experiment on a January 2024 research paper by [Tomislav Begušić] and colleagues as published in Science Advances. These researchers also used a classical tensor network to run the IBM experiment many times faster and more accurately, which the anonymous researcher(s) took as the basis for a version that runs on the C64 in a mere 15 kB of RAM, with the code put on an Atmel AT28C256 ROM inside a cartridge which the C64 then ran from.

The same sparse Pauli dynamics algorithm was used as by [Tomislav Begušić] et al., with some limitations due to the limited amount of RAM, implementing it in 6502 assembly. Although the C64 is ~300,000x slower per datapoint than a modern laptop, it does this much more efficiently than the quantum processor, and without the high error rate. Yes, that means that a compute cluster of Commodore 64s can likely outperform a ‘please call us for a quote’ quantum system depending on which linear algebra problem you’re trying to solve. Quantum computers may yet have their application, but this isn’t it, yet.

Thanks to [Stephen Walters] and [Pio] for the tip.

AM Radio Broadcast Uses Phasor To Let Eight Towers Spray One Big Signal

April 20, 2024 by 6 Comments

If you’re in the commercial AM radio business, you want to send your signal as far and wide as possible. More listeners means you can make more ad revenue, after all. [Jeff Geerling] recently visited a tower site for WSDZ-AM, which uses a full eight towers to broadcast its 20kW AM signal. To do that, it needs a phasor to keep everything in tune. Or, uh… phase.

The phasor uses a bunch of variable inductors and capacitors to manage the phase of the signal fed to each tower. Basically, by varying the phase of the AM signal going to each of the 8 transmitter towers, it’s possible to tune the directionality of the tower array. This allows the station to ensure it’s only broadcasting to the area it’s legally licensed to do so.

The tower array is also configured to broadcast slightly differently during the day and at night to account for the differences in propagation that occur. A certain subset of the 8 towers are used for the day propagation pattern, while a different subset is used to shape the pattern for the night shift. AM signals can go far farther at night, so it’s important for stations to vary their output to avoid swamping neighbouring stations when the sun goes down.

[Jeff’s] video is a great tour of a working AM broadcast transmitter. If you’ve ever wondered about the hardware running your local commercial station, this is the insight you’re looking for. AM radio may be old-school, but it continues to fascinate us to this day. Video after the break.

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Solar Panel Keeps Cheap Digital Calipers Powered Up

April 20, 2024 by 36 Comments

There’s no doubt that cheap digital calipers are useful, especially when designing 3D-printed parts. Unfortunately, cheap digital calipers are also cheap, and tend to burn through batteries quickly. Sure, you can remove the battery when you’re done using them, but that’s for suckers — winners turn to solar power to keep their calipers always at the ready.

[Johan]’s solar upgrade begins with, unsurprisingly, a solar cell, one that just fits on the back of his digital calipers. Like most of these cheap calipers, this one is powered by a single 1.5 V LR44 button cell, while the polycrystalline solar cell is rated for 5 V, so [Johan] used a red LED as a crude voltage regulator. He also added a stack of fourteen 100 μF SMD capacitors soldered together in parallel. The 1206 devices form a 1,400 μF block that’s smaller than the original button cell so that everything fits in the vacated battery compartment. It’s pretty slick.

Given their agreeable price point, digital calipers are a tempting target for hacking. We’ve seen a ton of them, from accessibility add-ons to WiFi connectivity and even repurposing them for use as DROs. Ever wonder how these things work? We’ve looked at that, too.