Grid overlayed onto a mason jar. Across the grid are high voltage purple coronas.

High Voltage For Extreme Ozone

May 21, 2025 by 3 Comments

Don’t you hate it when making your DIY X-ray machine you make an uncomfortable amount of ozone gas? No? Well [Hyperspace Pirate] did, which made him come up with an interesting idea. While creating a high voltage supply for his very own X-ray machine, the high voltage corona discharge produced a very large amount of ozone. However, normally ozone is produced using lower voltage, smaller gaps, and large surface areas. Naturally, this led [Hyperspace Pirate] to investigate if a higher voltage method is effective at producing ozone.

Using a custom 150kV converter, [Hyperspace Pirate] was able to test the large gap method compared to the lower voltage method (dielectric barrier discharge). An ammonia reaction with the ozone allowed our space buccaneer to test which method was able to produce more ozone, as well as some variations of the designs.

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[Austin Blake] sitting on line follower cart in garage

Honey, I Blew Up The Line Follower Robot

May 21, 2025 by 6 Comments

Some readers may recall building a line-following robot during their school days. Involving some IR LEDs, perhaps a bit of LEGO, and plenty of trial-and-error, it was fun on a tiny scale. Now imagine that—but rideable. That’s exactly what [Austin Blake] did, scaling up a classroom robotics staple into a full-size vehicle you can actually sit on.

The robot uses a whopping 32 IR sensors to follow a black line across a concrete workshop floor, adjusting its path using a steering motor salvaged from a power wheelchair. An Arduino Mega Pro Mini handles the logic, sending PWM signals to a DIY servo. The chassis consists of a modified Crazy Cart, selected for its absurdly tight turning radius. With each prototype iteration, [Blake] improved sensor precision and motor control, turning a bumpy ride into a smooth glide.

The IR sensor array, which on the palm-sized vehicle consisted of just a handful of components, evolved into a PCB-backed bar nearly 0.5 meters wide. Potentiometer tuning was a fiddly affair, but worth it. Crashes? Sure. But the kind that makes you grin like your teenage self. If it looks like fun, you could either build one yourself, or upgrade a similar LEGO project.
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Field Testing An Antenna, Using A Field

May 21, 2025 by 9 Comments

The ARRL used to have a requirement that any antenna advertised in their publications had to have real-world measurements accompanying it, to back up any claims of extravagant performance. I’m told that nowadays they will accept computer simulations instead, but it remains true that knowing what your antenna does rather than just thinking you know what it does gives you an advantage. I was reminded of this by a recent write-up in which the performance of a mylar sheet as a ground plane was tested at full power with a field strength meter, because about a decade ago I set out to characterise an antenna using real-world measurements and readily available equipment. I was in a sense field testing it, so of course the first step of the process was to find a field. A real one, with cows. Continue reading “Field Testing An Antenna, Using A Field” →

A New Mac Plus Motherboard, No Special Chips Required

May 21, 2025 by 29 Comments

The Macintosh Plus was Apple’s third version on the all-in-one Mac, and for its time it was a veritable powerhouse. If you don’t have one here in 2025 there are a variety of ways to emulate it, but should you wish for something closer to the silicon there’s now [max1zzz]’s all-new Mac Plus motherboard in a mini-ITX form factor to look forward to.

As with other retrocomputing communities, the classic Mac world has seen quite a few projects replacing custom parts with modern equivalents. Thus it has reverse engineered Apple PALs, a replacement for the Sony sound chip, an ATtiny based take on the Mac real-time clock, and a Pi Pico that does VGA conversion. It’s all surface mount save for the connectors and the 68000, purely because a socketed processor allows for one of the gold-and-ceramic packages to be used. The memory is soldered, but with 4 megabytes, this is well-specced for a Mac Plus.

At the moment it’s still in the prototype spin phase, but plenty of work is being done and it shows meaningful progress towards an eventual release to the world. We are impressed, and look forward to the modern takes on a Mac Plus which will inevitably come from it. While you’re waiting, amuse yourself with a lower-spec take on an early Mac.

Thanks [DosFox] for the tip.

Big Chemistry: Fuel Ethanol

May 21, 2025 by 73 Comments

If legend is to be believed, three disparate social forces in early 20th-century America – the temperance movement, the rise of car culture, and the Scots-Irish culture of the South – collided with unexpected results. The temperance movement managed to get Prohibition written into the Constitution, which rankled the rebellious spirit of the descendants of the Scots-Irish who settled the South. In response, some of them took to the backwoods with stills and sacks of corn, creating moonshine by the barrel for personal use and profit. And to avoid the consequences of this, they used their mechanical ingenuity to modify their Fords, Chevrolets, and Dodges to provide the speed needed to outrun the law.

Though that story may be somewhat apocryphal, at least one of those threads is still woven into the American story. The moonshiner’s hotrod morphed into NASCAR, one of the nation’s most-watched spectator sports, and informed much of the car culture of the 20th century in general. Unfortunately, that led in part to our current fossil fuel predicament and its attendant environmental consequences, which are now being addressed by replacing at least some of the gasoline we burn with the same “white lightning” those old moonshiners made. The cost-benefit analysis of ethanol as a fuel is open to debate, as is the wisdom of using food for motor fuel, but one thing’s for sure: turning corn into ethanol in industrially useful quantities isn’t easy, and it requires some Big Chemistry to get it done.
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A Look Inside A Lemon Of A Race Car

May 21, 2025 by 7 Comments

Automotive racing is a grueling endeavor, a test of one’s mental and physical prowess to push an engineered masterpiece to its limit. This is all the more true of 24 hour endurance races where teams tag team to get the most laps of a circuit in over a 24 hour period. The format pushes cars and drivers to the very limit. Doing so on a $500 budget as presented by the 24 hours of Lemons makes this all the more impressive!

Of course, racing on a $500 budget is difficult to say the least. All the expected Fédération Internationale de l’Automobile (FIA) safety requirements are still in place, including roll cage, seats and fire extinguisher. However, brakes, wheels, tires and safety equipment are not factored into the cost of the car, which is good because an FIA racing seat can run well in excess of the budget. Despite the name, most races are twelve to sixteen hours across two days, but 24 hour endurance races are run. The very limiting budget and amateur nature of the event has created a large amount of room for teams to get creative with car restorations and race car builds.

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