Radio Frequency Burns, Flying A Kite, And You

April 21, 2024 by Lewin Day 22 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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AM Radio Broadcast Uses Phasor To Let Eight Towers Spray One Big Signal

April 20, 2024 by Lewin Day 8 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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Bad Experiences With A Cheap Wind Turbine

April 20, 2024 by Lewin Day 44 Comments

If you’ve got a property with some outdoor space and plenty of wind, you might consider throwing up a windmill to generate some electricity. Indeed, [The Broject List] did just that. Only, his experience was a negative one, having purchased a cheap windmill online. He’s warning off others from suffering the same way by explaining what was so bad about the product he bought.

The windmill in question was described as a “VEVOR Windturbine”, which set him back around 100 euros, and claimed to be capable of producing 600 watts at 12 volts. He starts by showing how similar turbines pop up for sale all over the Internet, with wildly inflated specs that have no relation to reality. Some sellers even charge over 500 euros for the same basic device.

He then demonstrates the turbine operating at wind speeds of approximately 50 km/h. The output is dismal, a finding also shared by a number of other YouTube channels out there. Examining the construction of the wind turbine’s actual generator, he determines that it’s nowhere near capable of generating 600 watts. He notes the poorly-manufactured rotor and aluminium coils as particular disappointments. He concludes it could maybe generate 5 watts at most.

Sadly, it’s easy to fall into this trap when buying online. That’s where it pays to do your research before laying down your hard-earned cash. Continue reading “Bad Experiences With A Cheap Wind Turbine” →

Building A Giant Boardgame Isn’t Easy

April 19, 2024 by Lewin Day 8 Comments

[Stevenson Streeper] is a maker, and was recently charged with a serious mission. He had to prototype, design, and build a board game. A software-controlled board game, that is, and one that was 400 square-feet in size. As you might imagine, this ended up being a tall order, and he’s been kind enough to share his tale on his blog.

His client’s idea was for a giant interactive game board akin to the glowing disco floors of old. It had to play a game approximating the rules of “The Floor Is Lava.” It had to handle up to 20 players at a time, too.

[Stevenson] runs a company that delivers “Activations”—basically big showpieces for customers willing to pay. This wasn’t his first attempt at building an immersive attraction, but it was a big job, and a challenging one at that. He explains the difficulties that came about from a limited crew, limited timeline, and a number of difficult missteps. Hurdles included surprise unusable off-the-shelf hardware and the difficulty of hand-sanding 144 tiles of polycarbonate. One weeps for the project’s plight early on – if only the AliExpress tiles were documented.

He may have bitten off more than he could chew, and yet—the project was finished and to a decent degree of functionality success. That’s to be applauded, and [Stevenson] learned a ton along the way. Big projects can be daunting and can put you in a bind. As this story demonstrates, though, perseverance often gets you somewhere okay in the end. Video after the break.

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Roboticizing An Etch-a-Sketch

April 19, 2024 by Lewin Day 7 Comments

The Etch-a-Sketch was a popular toy, but a polarizing one. You were either one of those kids that had the knack, or one of the kids that didn’t. [Micah] was pretty firmly in the latter group, so decided to roboticize the Etch-a-Sketch so a computer could draw for him instead.

The build uses a pair of stepper motors attached to the Etch-a-Sketch’s knobs via 3D-printed adapters. It took [Micah] a few revisions to get the right design and the right motors for the job, but it all came together. A Raspberry Pi is charged with driving the motors to draw the desired picture.

Beyond the mechanics, [Micah] also does a great job of explaining the challenges around drawing and the drive software. Namely, the Etch-a-Sketch has a major limitation in that there’s no way to move the stylus without drawing a line. He accounts for this in his code for converting and drawing images.

The robot draws slowly but surely. The final result is incredibly impressive, and far exceeds what most of us could achieve on by hand. We’ve seen some similar builds in the past, too. Video after the break.

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Ultra-Tiny Wii Uses Custom Parts And Looks Amazing

April 19, 2024 by Lewin Day 17 Comments

The Nintendo Wii was never a large console. Indeed, it was smaller than both the Xbox 360, PlayStation 3, and most consoles of previous generations, too. That’s not to say it couldn’t be smaller, though. [loopj] has built what is perhaps the smallest Wii yet, which measures roughly the same size as a deck of cards. The best bit? The housing is even to scale!

There’s no emulation jiggery-pokery here. This build uses an original Wii motherboard that’s been cut down to the bare basics. Measuring just 62 mm by 62 mm, it features the CPU, GPU, RAM, and flash memory, while most of the extraneous hardware has been eliminated. Power and data is provided to the board from a special Wii Power Strip PCB, while the Periphlex flex PCB handles breaking out controller interfaces. Indeed, the build is nicknamed Short Stack as it’s built from a number of specialist PCBs for builds like this one. It also uses two boards designed by [YveltalGriffin] — the fujiflex for HDMI video output and the nandFlex to handle the Wii’s NAND memory chip.

[loopj] also had to design two further PCBs specifically for this build. One handles power, the micro SD card, HDMI connector, and controller ports. Meanwhile, the second handles the power, reset, and sync buttons along with status LEDs. Another neat hack of [loopj]’s own devising is using TRRS connectors in place of the original bulky GameCube controller ports.

Ultimately, it’s volume is just 7.4% that of an original Nintendo Wii. It’s probably possible to go smaller, too, says [loopj], so don’t expect things to end here. We’ve seen some other great Wii mods before, too, like this excellent handheld design.

Build Your Own RGB Fill Light For Photography

April 19, 2024 by Lewin Day 12 Comments

Photography is all about light, and capturing it for posterity. As any experienced photographer will tell you, getting the right lighting is key to getting a good shot. To help in that regard, you might like to have a fill light. If you follow [tobychui]’s example, you can build your own!

The build relies on addressable WS2812B LEDs as the core of the design. While they’re not necessarily the fanciest LEDs for balanced light output, they are RGB LEDs, so they can put out a ton of different colors for different stylistic effects. The LEDs are under the command of a Wemos D1, which provides a WiFI connection for wireless control of the light.

[tobychui] did a nice job of building a PCB for the project, including heatsinking to keep the array of 49 LEDs nice and cool. The whole assembly is all put together inside a 3D printed housing to keep it neat and tidy. Control is either via onboard buttons or over the WiFi connection.

Files are on GitHub if you’re seeking inspiration or want to duplicate the build for yourself. We’ve seen some other similar builds before, too. Meanwhile, if you’re cooking up your own rad photography hacks, don’t hesitate to let us know!