Math, Optics, And CNC Combine To Hide Secret Images In Acrylic

August 23, 2021 by Dan Maloney 45 Comments

Magic mirrors, with an LCD panel hidden behind a partially reflectively mirror, are popular for a reason — they’re a good-looking way to display useful information. A “Magic Window,” however, is an entirely different thing — and from the look of it, a far cooler one.

If you’ve never seen a Magic Window before, don’t worry — it’s partially because you’re not supposed to see it. A Magic Window appears to be a clear piece of glass or plastic, one with a bit of a wave in it that causes some distortion when looking through it. But as [Matt Ferraro] explains, the distortion encodes a hidden image, visible only when light passes through the window. It looks a bit like a lithophane, but it’s projected rather than reflected, and it relies on an optical phenomenon known as caustics. If you’ve ever seen the bright and dark patches cast on the bottom of a swimming pool when sunlight hits the surface, you’ve seen caustics.

As for how to hide an image in a clear window, let’s just say it takes some doing. And some math; Snell’s Law, Fermat’s Theorem, Poisson’s Equation — all these and more are mentioned by [Matt] by way of explanation. The short story is that an image is morphed in software, normalized, and converted into a heightmap that’s used to generate a toolpath for a CNC router. The design is carved into a sheet of acrylic by the router and polished back to clarity with a succession of sandpaper grits. The wavy window is then ready to cast its hidden shadow.

Honestly, the results are amazing, and we marvel at the skills needed to pull this off. Or more correctly, that [Matt] was able to make the process simple enough for anyone to try.

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Re-Engineering An RC Helicopter Via Tinkercad

August 20, 2021 by Lewin Day 5 Comments

Radio control toys can be great fun to play with. However, at the bottom end of the market, sometimes you find you’ve bought something that just doesn’t work quite right. [saulemmetquinn] found that with a cheap RC helicopter, and set about re-engineering the design in Tinkercad.

The entire frame of the original helicopter was discarded, replaced with one made out of CAD-designed and 3D printed components. The end result is far lighter and less cumbersome than the original design, while also managing to look a lot more like an actual helicopter. It also served to correct some of the problems which [saulemmetquinn] stated made the original toy difficult to fly.

Assembling your own tiny helicopter motors and mechanisms would be quite difficult, and time consuming. [saulemmetquinn] was instead able to leverage the good parts of the original design, and build something better from that. It’s very much the essence of hacking, right there.

We’ve seen other toy helicopters hacked too, like the famous Syma S107G. If you’ve got your own tiny flying hacks, be sure to drop us a line.

Airdropping Live Fish Is A Thing And It Looks Magnificent

August 18, 2021 by Lewin Day 52 Comments

Utah is a place that features a wonderful and varied wilderness. Its mountainous terrain is home to many valleys, ponds, and streams. They’re a particular favorite of recreational anglers who visit the region for the great fishing. Oftentimes, however, these areas are fished out by visitors and need to be restocked. Other environmental factors also come into play in reducing populations, too.

A plane delivering live fish to the lakes of Utah via air drop. Source: Utah DWR

When this happens in some areas, it’s as simple as driving up a truck full of water and fish and dumping them into the lake. The problem is that many of these lakes and streams are difficult to access by foot or by road. Believe it or not, the most practical method found to deal with the problem thus far is dropping in live fish by air. Here’s how it all goes down.

Live Cargo

Typically, the fish dropped into these remote watercourses are quite young, and on the order of 1-3″ long. The fish are specifically raised to later be fished, and are also usually sterile, making it easier for Utah’s Division of Wildlife Resources to manage numbers. When it comes time to restock remote lakes, waterbombing planes are pumped full of water and loaded up with fish.

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Running Six VGA Projectors From A Single ESP32

August 18, 2021 by Lewin Day 6 Comments

Today’s microcontrollers are high-speed powerhouses that can do absolutely wonderous things. By virtue of fast clock speeds and special DMA hardware, it’s often possible to achieve great feats that seem almost ridiculous at face value. [Bitluni] decided to demonstrate just that, running six (6!) VGA displays from a single ESP32. (Video, embedded below.)

The ESP32 clocks in at 240 MHz at top speed. It also features some nifty DMA hardware along with GPIO mapping that makes it perfectly suited to this task. [Bitluni] was thus able to set it up to drive up to six VGA displays at one bit per pixel monochrome output. Alternatively, ganging up six output pins into two sets of three, he was able to run two VGA displays with 3-bit color. The resolution is an impressive 640 x 400 in both cases, and [Bitluni] demonstrated the hardware by driving six projectors with a starfield display.

Is it useful? Perhaps not yet, but there’s certainly a few applications we could think of. Share your own ideas in the comments. In the meantime, check out [Bitluni]’s other great works for the ESP32.

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Solving Ultra High Vacuum Leaks Has An Elementary Solution

August 16, 2021 by Ryan Flowers 34 Comments

When we think of a vacuum leak we generally think of a car that just doesn’t want to run quite right. Most normally aspirated internal combustion engines rely on the vacuum created by the pistons to draw in the air fuel mixture that’s produced by the carburetor or fuel injection system. Identifying the leak usually involves spraying something combustible around common trouble areas while the engine is running. Changes to the engine speed indicate when the combustible gas enters the intake manifold and the leak can be found.

What if your vacuum leak is in a highly specialized piece of scientific equipment where the pressures are about 12 ~~times~~ orders of magnitude lower than atmospheric pressure, and the leak is so small it’s only letting a few atoms into the vacuum chamber at a time? [AlphaPhoenix] takes dives deep into this very subject in his video “Air-tight vs. Vacuum-tight.” which you can watch below the break.

Not only does [AlphaPhoenix] discuss how a perfect pressure vessel is sealed, he also explains the specialized troubleshooting methods used which turn out not to be all that different from troubleshooting an automotive vacuum leak- only in this case, several magnitudes more complex and elemental in nature.

We also enjoyed the comments section, where [AlphaPhoenix] addresses some of the most common questions surrounding the video: Torque patterns, the scarcity of the gasses used, and leaving well enough alone.

Does talking about vacuums get you pumped? Perhaps you’d enjoy such vacuum hacks as putting the toothpaste back in the tube in your homemade vacuum chamber.

Thank you [Morgan] for sending this one in. Be sure to send in your own hacks, projects, and fantastic finds through the Tip Line!

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Light Painting With An 19th Century Inspired Plotter

August 15, 2021 by Lewin Day 9 Comments

The geometric chuck was a device that stacked up multiple rotating wheels that could vary their speed and their offset to a central shaft, in order to machine ornate designs using a lathe. It’s this piece of machining obscura from the 19th century that inspired this light painting build from [Ted Kinsman].

Rather than the complicated gears and wheels used in the distant past, [Ted] instead elected to use stepper motors. Three stepper motors are stacked on top of each other, each one able to rotate at an independent rate. The design only implements three steppers as the slip rings needed to send power and control signals to each stepper are prohibitively expensive.

An Arduino is programmed to run the show, changing the speed of each motor and thus the patterns the system generates. Put LEDs on the spinning plates, or install a pen to mark a piece of paper, and it’s possible to generate all manner of beautiful spirograph-like patterns. Vary the motor speeds or the positioning of the lights, and the patterns vary in turn.

It’s a fun build for light painting, with some great visuals produced. We also appreciate the use of the Arduino which makes varying the parameters far easier than having to change out gearsets in classical designs.

If you miss the old school spirograph, you can always build one out of Lego. Else, consider experimenting with other light painting techniques. If you’ve built a fancy rig of your own, be sure to let us know!

[Thanks to zit for the tip!]

Materials For Self Learners

August 11, 2021 by Chris Lott 13 Comments

[João Nuno Carvalho] is a passionate learner. Software engineer by day, he studies all different branches of science and engineering in his spare time. He has organized an impressive list of study / reference materials on a wide variety of subjects that interest him, from aeronautical engineering to quantum mechanics and dozens more in between. In fact, his study lists themselves became so numerous that he collected them into a list of lists, which can be found here on his GitHub repository. These include categories on “How to learn…”

Modern Electronics
Modern Linux
Modern Embedded Systems
Mathematics from the ground up
Physics from the ground up
Modern Compressive Sensing
Modern [C, C++, Rust, Python]
Modern Machine Learning
Modern Aeronautics and Astronautics
Guitar on a budget

Another interesting thing we found in his repo was a list of common electrical components. If you can’t remember off the top of your head the part number of common 100 V PNP bipolar transistor, [João]’s list will point you towards a BD136.

It’s quite an impressive list of resources, and we can’t help but wonder how large [Joã0]’s personal library is if it contains even half of the materials from these lists. Check these out if you want to brush up on a topic — they include not only text books and reference volumes, but forums, blogs, YouTube links, etc. On the topic of learning, we wrote a piece back in 2017 on how learning differs between hobbyists and students. Do you have a favorite list-of-lists that you turn to when you want to brush up or learn about a new subject? Let us know in the comments below.