Plastics took off in the 20th century, with the new class of materials finding all manner of applications that metal, wood and paper simply couldn’t deliver on. Every field from electronics to the packaging of food found that plastics could play a role.
Now, over 150 years since the development of Parkesine in 1867, we’re now realizing that plastics come with more than a few drawbacks. They don’t break down well in nature, and now microplastics are beginning to appear all over the Earth, even in places where humans rarely tread. It seems they may even spread via the air, so let’s take a look at this growing problem and what can be done about it.
Some of the coolest sounds come from wild instruments like orchestra strings, fretless basses, and theremins — instruments that aren’t tied down by the constraints of frets and other kinds of note boundaries. [XenonJohn]’s air harp is definitely among this class of music makers, all of which require a certain level of manual finesse to play well.
Although inspired by Jean-Michel Jarre’s laser harp, there are no lasers here. This is a MIDI aetherharp, aka an air harp, and it is played by interrupting the signals from a set of eight infrared distance sensors. These sensors can be played at three different heights for a total of 24 notes, plus there’s a little joystick for doing pitch bends.
Inside the wooden enclosure of this aetherharp is a Teensy 3.5 and eight infrared distance sensors with particularly long ranges. On top is a layer of red acrylic that doesn’t affect the playability, except in bright sunlight. Although you could use most any MIDI software to produce the actual sounds, [XenonJohn] chose VMPK (Virtual MIDI Piano Keyboard). Be sure to check it out in action after the break.
Air cannons are fun, and became a part of mainstream culture with the popular Airzooka toy. Of course, cocking and firing the Airzooka gets tiring after a while, and they’re kind of a little small. This build from [1alembic] delivers on both those counts.
Cool, huh?
The result is a bigger air cannon that repeatedly fires all by itself. The cannon itself is built out of a trash can with the bottom cut out. It’s then fitted with a diaphragm made out of a heavy-duty trash bag covered in duct tape for added strength. Latex hose is then installed inside the trash can, attached to the diaphragm. Thus, the diaphragm can be pulled back, and when released, it’s pulled forward, creating a rush of air through the trash can which generates a vortex ring just like the smaller Airzooka.
The automation of the cannon is beautifully simple. A string is attached to the back of the diaphragm, and wrapped around a rod so it can be wound up. This allows a wiper motor to turn the rod via a set of gears, pulling the diaphragm back.
However, the drive gear on the wiper motor has half its teeth missing. The system is then set up so that once the diaphragm is pulled right back, the drive gear gets to the missing teeth, allowing the winder rod to spin back freely as the diaphragm shoots forward, firing the air cannon. The cycle then repeats as the drive gear re-engages the winding mechanism.
Paired with a smoke machine, the air cannon will whirr away, firing beautiful smoke rings at regular intervals until it’s switched off. It’s an elegant thing that we’d love to leave set up at a party to add some atmosphere. We’ve seen other air cannons built with some real fire-power, too. Video after the break.
For some reason, wildfire seasons in Australia, North America, and other places around the world seem to happen more and more frequently and with greater and greater fervor. Living in these areas requires special precautions, even for those who live far away from the fires. If you’re not sure if the wildfires are impacting your area or not, one of the tools you can build on your own is an air quality meter like [Costas Vav] shows us in this latest build.
The air quality indicator is based around an Adafruit Feather RP2040 which is in turn based on the 32-bit Cortex M0+ dual core processor. This makes for a quite capable processor in a small package, and helps accomplish one of the design goals of a rapid startup time. Another design goal was to use off-the-shelf components so that anyone could easily build one for themselves, so while the Feather is easily obtained the PMS5003 PM2.5 air quality sensor needed to be as well. From there, all of the components are wrapped up in an easily-printed enclosure and given a small (and also readily-available) OLED screen.
[Costas Vav] has made all of the files needed to build one of these available, from the bill of materials to the software running on the Pi-compatible board to the case designs. It’s a valuable piece of technology to have around even if you don’t live in fire-prone areas. Not only can wildfire smoke travel across entire continents but simple household activities such as cooking (especially with natural gas or propane) can decimate indoor air quality. You can see that for yourself with an army of ESP32-based air quality sensors.
I’m always amazed that technology can totally wipe out industries. Sure, some people make a living making horseshoes, for example, but the demand for them is way down compared to what it would have been when horses were the normal mode of transportation. But even so, people still make horseshoes. But think about the ice harvesting business. Never heard of it? Turns out, before refrigeration, there was a huge business of moving ice from where it naturally occurred to other places and storing it, usually underground with a lot of insulation. As far as I know, that business — including the neighborhood ice man — is totally gone now except for some historical exhibitions. We take refrigeration and air conditioning for granted, but it hasn’t been that long ago that ice was a luxury and your own reprieve from the heat was a fan.
Early Cooling
The story starts a little earlier than you might expect. In the 1840s, physician John Gorrie was concerned about “the evils of high temperature.” His hospital in Florida imported ice using the aforementioned ice trade and it wasn’t cheap nor was it very effective.
Undeterred, he developed a machine that used a horse, a waterwheel, steam, or wind power to drive a compressor to create ice. He got a patent in 1851 but it failed to catch on before his financial backer died. In fact, Oliver Evans had the idea in 1805 but never built a working machine. Jacob Perkins patented the first compression cooler in 1834, again with little practical use.
When U.S. President Garfield was shot, Navy engineers built a cooling box using cloths soaked in ice water to cool the president’s hospital room by 20 degrees. Since the mortally wounded president survived 80 days after the shooting, we presume he appreciated the comfort.
If there’s one this we electronics engineers are precious about, it’s our test gear. The instruments themselves can be obscenely expensive, since all that R&D effort needs to be paid back over a much smaller user base compared to say a DVD player. The test probes themselves can often come with an eye-watering price tag as well. Take the oscilloscope probe, pretty much everyone who tinkers with hardware will be familiar with. It’s great for poking around, looking desperately for inspiration when you’re getting stuck in with some debug, but you’ve only got two hands, and that doesn’t leave any spare for button pushing.
Hands-free probing solutions exist, but they can be pricey, flimsy or just a pain to use. Sometimes you just want to solder a wire and leave the probe attached, hoping the grounding lead doesn’t fall off and short something. We’ve seen many solutions to this, so here’s yet another one you can 3D print yourself, so it’s almost free to make.
The two-part 3D printed assembly embeds a pair of wires with a Molex 0008500113 sprung terminal on one end, which can be terminated with your choice of pins, headers or just a pair of plain ‘ol wires. Once you’ve dropped your wiring of choice inside, simply glue the halves with a little cyanoacrylate and you’re good to go. Designed around the Siglent 200MHz PP215 specifically, it is likely compatible with many other brands. Thingiverse only has STL files (sigh!) so it may be tricky to adapt it to your exact probe dimensions, but the idea is good at least.
We always get excited when we buy a new tablet. But after a few months, it usually winds up at the bottom of a pile of papers on the credenza, a victim of not being as powerful as our desktop computers and not being as convenient as our phones. However, if you don’t mind a thick tablet, you can get the RasPad enclosure to fit around your own Raspberry Pi so it can be used as a tablet. Honestly, we weren’t that impressed until we saw [RTL-SDR] add an SDR dongle inside the case, making it a very portable Raspberry Pi SDR platform.
The box is a little interesting by itself, although be warned it costs over $200. For that price you get an LCD and driver board, a battery system, speakers, and an SD extension slot with some control buttons for volume and brightness. There’s a video of the whole setup (in German) below.
