An RC Tank Chassis That’s Not Messing About

It’s not uncommon to see a tracked robot build on these pages, but it’s fair to say that many of them are somewhat on the small side. That was where [iforce2d] started, but the idea of making a more capable version just wouldn’t go away. Thus, he’s come back and made what looks to be a very promising, fully capable outdoor RC tank chassis, one that, within reason, we think should eventually be able to go anywhere.

For plenty of power, he’s using a pair of hoverboard motors with a chain reduction drive and in turn, a couple of shafts to the tracks. The chassis is a TIG-welded aluminium affair, while the tracks are an early incarnation with machined MDF drive wheels and a homemade tread. The suspension is a work of machined-aluminium art, though, and while there are teething troubles as he takes it for a spin, we can see plenty of potential as its deficiencies are ironed out.  Take a look at it in the video below the break.

If large-size R/C tanks are your thing, we have another for you to look at.

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A RISC-V Security Key

The TKey is a RISC-V-based security key that plugs into a USB port. The device has a number of features, including a device-specific serial number, RAM scrambling, and a monitor that kills the CPU in the event of access to protected memory. There is also an FPGA that, on the end-user version, is locked down. This prevents you from changing the core features and the unique ID number for the device.

As part of the start-up code, the device calculates a hash of the application and merges it with the device ID and, potentially, a user-defined secret. If this number matches a previous calculation, it is reasonably certain that nothing has changed between the times of the calculations.

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It’s Switch Mode, But Not As You Know It

The switch-mode power supply has displaced traditional supplies almost completely over the last few decades, being smaller, lighter, and more efficient. But that’s not to say that it’s a new idea, and on the way to today’s high-frequency devices there have been quite a few steps. An earlier one is the subject of a teardown video from [Thomas Scherrer OZ2CPU], as he takes a look at a 1960s HP power supply with a slightly different approach to regulation for the day. Instead of a linear regulator on its conventional transformer and rectifier circuit, it has a pair of SCRs in the mains supply that chop at mains frequency. It’s a switch mode supply, but not quite as you’re used to.

In fact, these circuits using an SCR or a triac weren’t quite as uncommon as you might expect, and could at one point be found in almost every domestic TV set or light dimmer. Sometimes referred to as “chopper” supplies, they represented a relatively cheap way to derive a regulated DC voltage from an AC mains source in the days before anyone cared too much about RF emissions, and though few were as high quality as the HP shown in the video below, they were pretty reliable.

If older switchers interest you, this is not the first one we’ve shown you from that era.

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Restoring The DC Bias

If you have a signal that passes through a capacitor or transformer, you will lose the DC portion of the signal. What do you do? If you need it, you can restore the DC bias using various techniques, as [Sam Ben-Yaakov] shows in a recent video.

These types of circuits were common in analog TVs, and, in fact, [Sam] shows the schematic of a TV to explain the need for the DC level. In that case, a vacuum tube diode does the work, but a solid state one will do the same job.

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China’s Nuclear-Powered Containership: A Fluke Or The Future Of Shipping?

Since China State Shipbuilding Corporation (CSSC) unveiled its KUN-24AP containership at the Marintec China Expo in Shanghai in early December of 2023, the internet has been abuzz about it. Not just because it’s the world’s largest container ship at a massive 24,000 TEU, but primarily because of the power source that will power this behemoth: a molten salt reactor of Chinese design that is said to use a thorium fuel cycle. Not only would this provide the immense amount of electrical power needed to propel the ship, it would eliminate harmful emissions and allow the ship to travel much faster than other containerships.

Meanwhile the Norwegian classification society, DNV, has already issued an approval-in-principle to CSSC Jiangnan Shipbuilding shipyard, which would be a clear sign that we may see the first of this kind of ship being launched. Although the shipping industry is currently struggling with falling demand and too many conventionally-powered ships that it had built when demand surged in 2020, this kind of new container ship might be just the game changer it needs to meet today’s economic reality.

That said, although a lot about the KUN-24AP is not public information, we can glean some information about the molten salt reactor design that will be used, along with how this fits into the whole picture of nuclear marine propulsion.

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An exploded view render of a red 3D printed case with a green PCB is inside with visible USB-A connectors with a mouse and keyboard graphic above each and "A" and "B" labels above USB-C connectors on the other side.

Building A Better Keyboard And Mouse Switch

Switching inputs between desktops seems like something that should be simple but can prove to be a pain in reality. [Hrvoje Cavrak] decided to take matters into his own hands and build a better keyboard and mouse switch.

DeskHop is built from two Raspberry Pi Pico boards connected via UART and separated by an Analog Devices ADuM1201 dual-channel digital isolator. Through the magic of Pico-PIO-USB these RP2040s can be both host and device. To keep things simple, the PCB is single-sided, and the BOM only has five distinct components.

Once hooked up to your Windows, Mac, or Linux device, your mouse pointer “magically” goes from one screen to the other when dragged across the screen edge. Keyboard LEDs can be reprogrammed to indicate which device is active, and the real beauty of the device is that since it’s a hardware solution, you don’t have to install any software on a computer you might not have admin access to.

If you want to see some more ideas for keyboard and mouse switching, check out this Pi KVM with ATX signaling, this USB triplexer, or this Pi KVM on a PCIe card.

Game Graphics: Rasterization

Last time, I talked about racing the beam, a type of graphics used when memory was scarce. Now it’s time to step into the future with more memory and talk about what modern 2D games still do to this day: rasterization.

Just in time Memory

Continuing the trend set by racing the beam, rasterized graphics are also on a grid, just a much tinier one. Though not unique to rasterized, the “frame buffer” is the logical conclusion of bitmap mode fidelity: enough memory is allocated so that every pixel can have its own color. What’s different about a frame buffer is that everything is drawn before it is shown and, crucially, this doesn’t have to happen in the same order as the pixels are displayed. Rasterization draws entire shapes — triangles, lines and rectangles — into the frame buffer and the screen is typically updated all at once. Continue reading “Game Graphics: Rasterization”