A wooden robot with a large fresnel lens in a sunny garden

Gardening Robot Uses Sunlight To Incinerate Weeds

June 30, 2023 by Robin Kearey 36 Comments

Removing weeds is a chore few gardeners enjoy, as it typically involves long sessions of kneeling in the dirt and digging around for anything you don’t remember planting. Herbicides also work, but spraying poison all over your garden comes with its own problems. Luckily, there’s now a third option: [NathanBuildsDIY] designed and built a robot to help him get rid of unwanted plants without getting his hands dirty.

Constructed mostly from scrap pieces of wood and riding on a pair of old bicycle wheels, the robot has a pretty low-tech look to it. But it is in fact a very advanced piece of engineering that uses multiple sensors and actuators while running on a sophisticated software platform. The heart of the system is a Raspberry Pi, which drives a pair of DC motors to move the whole system along [Nathan]’s garden while scanning the ground below through a camera.

The Pi runs the camera’s pictures through a TensorFlow Lite model that can identify weeds. [Nathan] built this model himself by taking hundreds of pictures of his garden and manually sorting them into categories like “soil”, “plant” and “weed”. Once a weed has been detected, the robot proceeds to destroy it by concentrating sunlight onto it through a large Fresnel lens. The lens is mounted in a frame that can be moved in three dimensions through a set of servos. A movable lens cover turns the incinerator beam on or off.

Sunlight is focused onto the weed through a simple but clever two-step procedure. First, the rough position of the lens relative to the sun is adjusted with the help of a sun tracker made from four light sensors arranged around a cross-shaped cardboard structure. Then, the shadow cast by the lens cover onto the ground is observed by the Pi’s camera and the lens is focused by adjusting its position in such a way that the image formed by four holes in the lens cover ends up right on top of the target.

Once the focus is correct, the lens cover is removed and the weed is burned to a crisp by the concentrated sunlight. It’s pretty neat to see how well this works, although [Nathan] recommends you keep an eye on the robot while it’s working and don’t let it near any flammable materials. He describes the build process in full detail in his video (embedded below), hopefully enabling other gardeners to make their own, improved weed burner robots. Agricultural engineers have long been working on automatic weed removal, often using similar machine vision systems with various extermination methods like lasers or flamethrowers.

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Hydroplaning Boat Skims Over Water

June 29, 2023 by Lewin Day 3 Comments

Regular hulled boats are all well and good for rowing and all, but if you wanna go fast, you’ve gotta cut your draft. [RCLifeOn] built a hydroplane design that skims on the very surface of the water, and thus travels very quickly as a result.

The build came about as [RCLifeOn] has an upcoming race which he wishes to win with speed and finesse. To that end, he 3D printed an RC hydroplane, using spray paint and spackle to waterproof the parts. It’s a trimaran design, with the large central hull connected to two pontoons via carbon fiber rods. Propulsion is via a triple-motor fan setup on the rear of the boat.

The outer motors were initially used to steer the boat via variable thrust, which comes with zero drag penalty compared to a conventional rudder. However, they proved ineffective, and a servo driven rudder was used instead. Eventually, all three motors were reconfigured for forward thrust.

The boat worked well when it was able to get up to speed and hydroplane over the surface of the water. However, it was difficult to film, as even the weight of a GoPro was enough to keep it stuck on the water’s surface. Instead [RCLifeOn] used his electric surfboard as a chase rig to film the boat — a neat trick itself. Continue reading “Hydroplaning Boat Skims Over Water” →

Spy Radio Setup Gets A Tiny Power Supply For Field Operations

June 29, 2023 by Dan Maloney 14 Comments

[Helge Fyske (LA6NCA)] may not be an actual spy — then again, he may be; if he’s good at it, we wouldn’t know — but he has built a couple of neat vacuum tube spy radios in the past. And there’s no better test for such equipment than to haul it out into the field and try to make some contacts. But how do you power such things away from the bench?

To answer that question, skip ahead to the 3:18 mark of the video below, where [Helge] shows off his whole retro rig, including the compact 250-volt power supply he built for his two-tube 80-m Altoids tin spy transceiver. In the shack, [Helge] powers it with a bench power supply of his own design to provide the high anode voltage needed for the tubes, as well as 12 volts for their heaters. Portable operations require a more compact solution, preferably one that can be run off a battery small enough to pack in.

By building his power supply in a tin, [Helge] keeps to his compact build philosophy. But the circuit is all solid state, which is an interesting departure for him. The switch-mode supply uses a 4047 astable multivibrator chip as a 50-kHz oscillator, which switches back and forth between a pair of MOSFETs to drive a transformer. This steps up the 12-volt input to 280 volts AC, which is then rectified, filtered, and regulated to 250 volts DC.

To round out his spy rig, [Helge] also designed a tiny Morse key, which appears to be 3D printed and fits in its own tin, and a compact dipole antenna. Despite picking what appears to be a challenging location — the bottom of a steep-sided fjord — [Helge] was easily able to make contacts over a distance of 400 km. His noise floor was remarkably low, a testament to the solid design of his power supply. Including the sealed lead acid battery, the whole kit is compact and efficient, and it’s a nice example of what vacuum tubes and solid state can accomplish together.

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Rubber Tracked Bicycle Is Horribly Inefficient

June 29, 2023 by Lewin Day 31 Comments

Wheeled bikes are efficient machines, and most cycling speed and distance records are held by them. However, [The Q] has a taste for weirder creations that amuse perhaps more than they serve as viable transportation. His latest experiments revolve around tracked propulsion methods.

The build is a wheelless bike that relies on long thin tracks mounted to a mountain bike frame. The tracks carriers are fabricated using steel box section fitted with cogged rollers. The tracks themselves are made using a pair of bicycle chains joined with welded steel bars. They’re fitted with slices of rubber cut out of traditional bike tires for grip. The rear track is driven from the bike’s pedals, while the front is merely left to run freely.

By virtue of its wide, flat tracks, the bike actually stands up on its own. It’s capable of riding in a straight line at slow speed, albeit relatively noisily. Steering is limited by virtue of the flat tracks, which don’t operate well at an angle to the ground. Since the tracks only contact the ground at a point, too, the bike has very high ground pressure, which would make it likely to sink into anything less solid than asphalt.

The build is relatively similar to [The Q]’s previous efforts to build a supposedly square-wheeled bike. What we’d really love to see at this point is a tracked bicycle that actually made the best of the technology – by being both swift and capable of crossing soft, marshy terrain. Video after the break.

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Build A DIY Space Mouse For A More Efficient CAD Workflow

June 29, 2023 by Lewin Day 21 Comments

When you find yourself doing a lot of work in 3D modelling, you occasionally wish for something more capable than the humble two-dimensional mouse. A space mouse is a great tool in this regard, and [Salim Benbouziyane] was inspired to build his own.

[Salim] started his work with research, by watching a teardown of a Connexion Space Navigator 3D mouse. This informed him of the basic functionality and the workings inside. The commercial product appears to use an optical sensor setup, but [Salim] decided to go with a magnetic sensor setup instead due to the parts he had on hand. Namely, a 3-axis magnetometer which seemed perfect for the task.

The build uses a motion platform mounted on six springs which translates and rotates in three dimensions as required. The magnetometer is mounted on the platform above a stationary set of neodymium magnets. Thus, when the platform, and thus sensor, moves, the magnetometer’s output can be used to determine the motion of the platform and translate that into useful viewport commands for CAD software. A RP2040 is charged with reading the magnetometer and acting as a USB HID device. It’s all wrapped up in a neat 3D-printed housing.

For now, it’s a little simpler in its operation than a full 6 DOF Spacemouse, but it nonetheless has helped [Salim]’s workflow improve. A good peripheral like this can be a real boon on the desktop; we’ve seen a few DIY projects in this realm for just that reason. Video after the break.

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Sci Fi UI Made Easy With Arwes

June 29, 2023 by Lewin Day 18 Comments

Many of us grew up watching Star Trek, marvelling at the beautiful colorful interfaces on the computers that ran the Starship Enterprise. Today’s computer interfaces have certainly grown fancier since the Windows 3.1 and Mac System 7 days, but they’re still nowhere near that gorgeous. The Arwes framework aims to change that, at least where web apps are concerned.

The framework is inspired by the cyberprep and synthwave aesthetics, while drawing from media like TRON: Legacy and Halo. You can get a peek at what it can do on the Arwes website, or look at how it runs on sites like SoulExtract or the Cyber Movie Database. It’s very much about glowing lines, 1980s computer sounds, and screens with animated text fills.

It’s still in an alpha release, and likely isn’t yet ready for business-critical production use. It currently consists of a set of basic components that can be assembled into a functional futuristic website design, but you’ll need some experience to use the tools at hand. There’s a sandbox for experimenting that should help in that regard.

You might just find that it’s the perfect tool to create an interface for your very own cyberdeck, or you might put it to work on your next website design. Either way, if you create something fantastic, don’t hesitate to drop us a line.

VCF’s Swap Meet Experiment Helps Support Expansion

June 29, 2023 by Tom Nardi 13 Comments

There was a time when those looking for tech bargains had to either try their luck at the local flea market, or make the pilgrimage out to a dedicated swap meet. But with the rise of websites like eBay and Craigslist these parking lot meetups started to fall out of favor, to the point that they became all but extinct over the last couple decades.

So there was some risk involved when the Vintage Computer Federation decided to dust off the concept as a way of sidestepping New Jersey’s COVID-era limitations on indoor meetups. But as VCF Vice President [Jeffrey Brace] explained during our visit earlier this month, the experiment has more than paid off. Each swap meet has brought in buyers and sellers from all over the Mid–Atlantic region, helping to not only raise money for the VCF’s ongoing preservation efforts, but spread awareness of the organization and their goals.

The VCF hopes to expand their existing museum.

During our chat, [Jeffrey] goes over the origins and growth of the VCF swap meet, and how it compares to their annual Vintage Computer Festival. He also speaks about the Federation’s desire to expand their already impressive museum space into a far larger climate-controlled area that will allow for even more classic computer hardware to be put on display.

We visited the VCF swap meet back in 2021, and came away with the distinct impression that [Jeffrey] and the rest of the team had a winning idea on their hands. We’re happy to report that as of 2023 the areas where we saw room for improvement — namely the lack of on-site refreshment and a somewhat overly narrow focus on vintage hardware — have both been addressed. In its current form, this is truly a must-see event for anyone with an interest in computers, radio, or even just general electronics who happens to live within driving distance of the Jersey shore.

While eBay certainly makes it easy to bid on a piece of gear, you’re unlikely to make a new friend while doing so. Events like this are more than just a way to buy and sell hardware, but provide a chance for like-minded individuals to connect and build a community. We’re glad to see the event grow larger each year, and hope it inspires similar revivals elsewhere.

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