Laser Tachometer Knows How Fast You Were Spinning Back There

Does your drill go as fast as the manufacturer says it will? Well, you’d need a tachometer to figure that out. They’re not that expensive to buy, but as [Elite Worm] shows, they’re not that expensive to make, either — about $10 total if you get your parts from the right places. Lucky for you, he has links to everything.

Really, the links are just the tip of the iceberg here as far as the gifts that [Elite Worm] bestows upon those who choose to undertake this project. The build video (after the break, as usual; our favor to you) is fantastic, and would be perfect for a beginner because of the entrancing speed at which he builds it. The video is straight up relaxing to watch, whether you want to build one or not.

It’s a fairly simple circuit — just push the momentary switch, and the laser diode and sensor pair count the revolutions over one second. The Arduino Nano multiplies this number by 60 and displays the RPM on the OLED screen. What we absolutely love about this build is the care that taken in designing the case. There’s a designated spot for each component, and the ones without their own special holder are kept in place with printed crossbar pieces. [Elite Worm] says this has a higher refresh rate than his store-bought tacho, and we say it looks way cooler, too.

Still don’t want to make one yourself? Well, okay. Before you buy one, try using your phone to calculate RPM.

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A Laser Drawing Machine For Flashes Of Creativity

Ahh, midterms. Some students blow off steam between study sessions by playing video games or just zoning out. While those kids were all distracted, [Justinwong777] and his buddy [Brett] found a bunch of scrap wood and built this laser drawing machine in their school’s makerspace. You operate it as you might an Etch-a-Sketch, except your drawings are as fleeting as sparkler art on the 4th of July, if they made Tron-colored sparklers.

Though you work it like an Etch-a-Sketch, the business end operates like a laser cutter. Inside that plywood enclosure is an Arduino Uno and a pair of motors. These motors turn a series of custom gears, which move a small mirror angled at 45° in the xy-plane.  There’s a 30mW laser mounted parallel with the base, pointed at the mirror, and it reflects the beam toward a canvas panel coated with phosphorescent paint. We dig the printed ergonomic case for the joystick, which gives control of both x and y. Put on some eye protection and check it out after the break.

If you want to draw with lasers, but aren’t much of an artist, do something unexpected: build a laser turret not to kill, but to draw the weather on the wall.

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Laser Etches Solar Absorbing Material

Having a laser cutter these days isn’t a big deal. But [Chunlei Guo], a professor at the University of Rochester, has a powerful femto-second pulse laser and used it to create what might be the perfect solar absorber. You can see a video about the work, below.

It stands to reason that white materials reflect most light and therefore absorb less energy than black materials — this is part of what makes a radiometer work. Tungsten, in particular, is a good metal for absorbing solar power, but this new laser treatment — which builds nanostructures on the surface of the metal — increases efficiency by 130% compared to untreated tungsten.

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Custom Laser Tag Rifle Packs A Sonic Punch

Laser tag is rarely (if ever) referred to as “The Sport of Kings”, but is a fun pastime nonetheless. While some are content to play with off-the-shelf toys, others prefer to make their own gear to suit their needs. [Heine Nielsen] is just one such builder, creating a fully-featured laser rifle loaded with features.

As far as hardware goes, [Heine]’s laser rifle is packed to the gills. There are two ESP32s running the show, along with a meaty 6S lithium battery to provide plenty of juice for long combat sessions. A 40W audio amp is hooked up to a speaker mounted in a faux-grenade launcher, aping the design of the M203 – and is able to deliver ear-splitting sound for that realistic touch.

Knowing the popularity of modern FPS games, [Heine] cribbed a lot from titles like PUBG and CS:GO. Grabbing sound effects from various weapons was just one step, with the ultimate goal being to replicate advanced game modes from these games. To help keep the player aware of the game state, there’s even a HUD on the gun, thanks to a 2.8″ TFT screen tucked into the scope.

It’s a serious build for playing serious laser tag, and we’d love to head out to the field for a match with gear like this. We’ve seen other hyper-realistic builds before too, like this one that uses actual blanks. Video after the break.

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Burning Things With Big Lasers In The Name Of Security

Several fields of quantum research have made their transition from research labs into commercial products, accompanied by grandiose claims. Are they as good as they say? We need people like Dr. Sarah Kaiser to independently test those claims, looking for flaws in implementation. At the 2019 Hackaday Superconference she shared her research on attacking commercially available quantum key distribution (QKD) hardware.

Don’t be scared away when you see the term “quantum” in the title. Her talk is very easy to follow along, requiring almost no prior knowledge of quantum research terminology. In fact, that’s the point. Dr. Kaiser’s personal ambition is to make quantum computing an inviting and accessible topic for everyone, not just elite cliques of researchers in ivory towers. You should hear her out in the video below, and by following along with the presentation slide deck (.PPTX).

Quantum Key Distribution

So why is QKD is so enticing? Unlike existing methods, the theoretical foundation is secure against any attacker constrained by the speed of light and the laws of physics.

Generally speaking, if your attacker is not bound by those things, we have a much bigger problem.

But as we know well, there’s always a difference between the theoretical foundation and the actual implementation of cryptography. That difference is where exploits like side-channel attacks thrive, so she started investigating components of a laser QKD system.

As a self-professed “Crazy Laser Lady”, part of this investigation examined how components held up to big lasers delivering power far outside normal operating range. This turned up exciting effects like a fiber fuse (~17:30 in the video) which is actually a plasma fire propagating through the fiber optic. It looks cool, but it’s destructive and useless for covert attacks. More productive results came when lasers were used to carefully degrade select components to make the system vulnerable.

If you want to learn more from Dr. Kaiser about quantum key distribution, she has a book chapter on the topic. (Free online access available, but with limitations.) This is not the first attempt to hack quantum key distribution, and we doubt it would be the last. Every generation of products will improve tolerance to attacks, and we’ll need researchers like our Crazy Laser Lady to find the reality behind advertised claims.

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Node-RED Laser Shooting Gallery Goes Anywhere

When you think of a shooting gallery, you might envision a line of tin cans set up along a split-rail fence, or a few rows of ducks or bottles lined up at a carnival. But what do these have in common? You, standing in one spot, and shooting in the same general direction. You’re exposed! If those targets could shoot back, you’d be dead within seconds. Wouldn’t it be more fun if the targets were all around you in 360°? We think so, too.

So how could you possibly set up a shooting gallery this way? [Another Maker] already solved that problem for you with ESP32s and Node-RED (YouTube). Each target has an ESP32, a laser sensor, and an LED that lights up when the target is ready, and turns off once it’s been hit. They all make an enticing ‘shoot me’ sound that goes with their graphics, and a second mp3 plays upon direct hit.

The PVC gun houses an ESP8266, a laser module at the end of the barrel, and runs on a cylindrical USB battery slipped down in the secondary grip. [Another Maker] can spread the targets out far and wide, as long as they all stay in range of the localized WiFi access point.

The best part is that the Node-RED system is target-agnostic — it doesn’t care how many you have or how they’re made, and it can juggle up to 250 of them. Because of the way the target objects are programmed, it would be quite easy to add actuators that make them drop down or fall backward when hit. You could also implement [Another Maker]’s fantastic suggestion of hitting arcade buttons with NERF darts instead. Charge those lasers and fire at the break button to see the demo and walk-through video.

If you plan to knock the targets down or over in your implementation, you’ll want an easy way to reset them. Here’s a scrap-built shooting gallery that uses a windshield wiper motor to set ’em back up.

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Word Clock Does The Job With Laser-Etched Acrylic

As far as telling the time, word clocks go out of their way to spell it out for you. As long as you know the language, they’re a stylish and effective way to get the message across. [Simon] built an elegant, stripped-back word clock of his own, with a laser cutter helping to get the job done.

The core of the build is an Arduino Nano, hooked up to a string of 22 WS2812B LEDs, driven via the FastLED library. An NXP PCF8563T serves as the real-time clock, to ensure stable and accurate timekeeping. The electronics are all housed inside an enclosure that appears to be constructed from PCBs, with instructions on operating the clock printed on the base.

The actual display is via laser-cut and laser-etched acrylic. The display piece slides into the top of the clock, with the LEDs edge lighting various segments to display the relevant words that make up the current time. The clock is designed in such a way that these display slides can be easily switched out to change the look of the clock, with different fonts and designs.

It’s a quick and clean take on the popular word clock design, and one any makerspace could whip up in a weekend. As far as word clocks go, however, the sky really is the limit when it comes to complexity. Video after the break.

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