Compact Sensor Keeps You Safe By Watching CO2 Levels

August 24, 2021 by Dan Maloney 21 Comments

Remember when work meetings were just a bunch of people filling up a small, poorly ventilated room with their exhaled breath? Back in the good old days, all you had to worry about was being lulled to sleep by a combination of the endless slide deck and the accumulation of carbon dioxide. Now? Well, the stakes may just be a little bit higher.

In either situation, knowing the CO₂ level in a room could be a handy data point, which is where a portable CO₂ sensor like this one could be useful. Or at least that’s [KaRMaN]’s justification for SYPHCOM, the “simple yet powerful handheld carbon dioxide meter.” The guts of the sensor are pretty much what you’d expect — an Arduino Pro Micro, a SenseAir S8 CO₂ sensor board, and the necessary battery and charging circuits. But the build does break the mold in a couple of interesting places. One is in the choice of display — a 1980s-era LED matrix display. The HDSP2000 looks like it belongs in a nice bench meter, and is surprisingly legible without a filter. It looks like it flickers a bit in the video below, but chances are that’s just a camera artifact.

The other nice part of this build is the obvious care [KaRMaN] put into making it as small as possible. The layout of boards and components is very clever, making this a solid, compact package, even without an enclosure. We’ve seen CO₂ sensors with more features, but for a quick check on air quality, SYPHCOM looks like a great tool.

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Fail Of The Week: Learning How Not To Silver Solder

August 24, 2021 by Dan Maloney 26 Comments

Sure, there are subtleties, but by and large it’s pretty easy to pick up soldering skills with a little practice. But wait! Not all soldering is created equal, and as [Quinn Dunki] learned, silver soldering is far harder to get right.

Granted, the job [Quinn] is working on is much more demanding than tacking some components to a PCB. She has been building a model steam engine, a task fit to put anyone’s machining skills to the test. And a steam engine needs a boiler, which is where the silver soldering comes in. As she explains in the video below, silver soldering, or “hard” soldering, uses solder that melts at a much higher temperature than “soft” solders like we’re used to in electronics. That’s a big advantage in the heat and pressure of a boiler, but it does pose some problems, many of which [Quinn] managed to discover as she tried to assemble her copper beast.

It turns out that heating a big hunk of copper evenly without burning off the flux actually isn’t that easy, though you can’t say she didn’t give it the old college try. In the process, she managed to share a number of tidbits that were really interesting, like the fact that drawing acetylene from a tank too fast can be dangerous, or that model steam boilers have to be certified by qualified inspectors. In the end, her boiler couldn’t be salvaged, and was put to the saw to determine the problem, which seems to be her initial choice of heating with oxyacetylene; after that initial failure, there was little she could do to save the boiler.

As [Quinn] says, “Failure is only failure if you don’t learn from it.” And so it may be a bit unfair to hang “Fail of the Week” on this one, but still — she has to go back to the beginning on the boiler. And we already know that model steam engines aren’t easy.

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Wooden Monowheel Build Is Simplicity Itself

August 23, 2021 by Dave Rowntree 9 Comments

Monowheels are nothing new, first being patented in the middle of the 19th century, but never really went mainstream due to, well, quite a lot of obvious issues. We’ve got problems with forward visibility, stability, steering, especially at speed, and the hilariously-named ‘gerbiling’ where the rider can spin around inside the wheel akin to a gerbil in a wheel. Fun times! But obviously that didn’t stop [The Q] from adding to the monowheel corpus by building one out of wood.

Sometimes people take on these projects simply for a laugh, like this bright orange one we covered a while back. Sometimes they’re powered by a motor, be it electric or internal combustion. Some are hand-cranked, some are pedal-powered, its all been tried.

[The Q] is no stranger to interesting wooden builds, and this video from a year ago shows him building a very simple direct-pedal-drive monowheel. The vast majority of the structure is wood, glued and screwed the old-fashioned way, with a bit of metalwork where necessary. We particularly like the simple counterweight solution which doubles up as a parking brake. It may look a little ungainly, but we can’t think of a simpler solution that would make much sense.

The build video after the break is six and half minutes of well executed videography for your viewing pleasure.

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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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