Rapid-Fire Hail Of Chopstick Arrows Makes Short Work Of Diminutive Foes

Many Hackaday readers may also be familiar with the Discworld series of fantasy novels from [Terry Pratchett], and thus might recognise a weapon referred to as the Piecemaker. A siege crossbow modified to launch a hail of supersonic arrows, it was the favoured sidearm of a troll police officer, and would frequently appear disintegrating large parts of the miscreants’ Evil Lairs to comedic effect.

Just as a non-police-officer walking the streets of Ank-Morpork with a Piecemaker might find swiftly themselves in the Patrician’s scorpion pit, we’re guessing ownership of such a fearsome weapon might earn you a free ride in a police car here on Roundworld. But those of you wishing for just a taste of the arrow-hail action needn’t give up hope, because [Turnah81] has made something close to it on a smaller scale. His array of twelve mousetrap-triggered catapults fires a volley of darts made from wooden kebab skewers in an entertaining fashion, and has enough force to penetrate a sheet of cardboard.

He refers to a previous project with a single dart, and this one is in many respects twelve of that project in an array. But in building it he solves some surprisingly tricky engineering problems, such as matching the power of multiple rubber bands, or creating a linkage capable of triggering twelve mousetraps (almost) in unison. His solution, a system of bent coat-hanger wires actuated by the falling bar of each trap, triggers each successive trap in a near-simultaneous crescendo of arrow firepower.

On one hand this is a project with more than a touch of frivolity about it. But the seriousness with which he approaches it and sorts out its teething troubles makes it an interesting watch, and his testing it as a labour-saving device for common household tasks made us laugh. Take a look, we’ve put the video below the break.

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Flagging Down Aliens With World’s Biggest Laser Pointer

As you’re no doubt aware, humans are a rather noisy species. Not just audibly, like in the case of somebody talking loudly when you’re in a movie theater, but also electromagnetically. All of our wireless transmissions since Marconi made his first spark gap broadcast in 1895 have radiated out into space, and anyone who’s got a sensitive enough ear pointed into our little corner of the Milky Way should have no trouble hearing us. Even if these extraterrestrial eavesdroppers wouldn’t be able to understand the content of our transmissions, the sheer volume of them would be enough to indicate that whatever is making all that noise on the third rock orbiting Sol can’t be a natural phenomena. In other words, one of the best ways to find intelligent life in the galaxy may just be to sit around and wait for them to hear us.

Of course, there’s some pesky physics involved that makes it a bit more complicated. Signals radiate from the Earth at the speed of light, which is like a brisk walk in interstellar terms. Depending on where these hypothetical listeners are located, the delay between when we broadcast something and when they receive it can be immense. For example, any intelligent beings that might be listening in on us from the closest known star, Proxima Centauri, are only just now being utterly disappointed by the finale for “How I Met Your Mother“. Comparatively, “Dallas” fans from Zeta Reticuli are still on the edge of their seats waiting to find out who shot J.R.

But rather than relying on our normal broadcasts to do the talking for us, a recent paper in The Astrophysical Journal makes the case that we should go one better. Written by James R. Clark and Kerri Cahoy,  “Optical Detection of Lasers with Near-term Technology at Interstellar Distances” makes the case that we could use current or near-term laser technology to broadcast a highly directional beacon to potentially life-harboring star systems. What’s more, it even theorizes it would be possible to establish direct communications with an alien intelligence simply by modulating the beam.

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[Ben Krasnow] Gasses MEMS Chips, For Science

Why in the world does helium kill iPhones and other members of the Apple ecosystem? Enquiring minds want to know, and [Ben Krasnow] has obliged with an investigation of the culprit: the MEMS oscillator. (YouTube, embedded below.)

When we first heard about this, courtesy in part via a Hackaday post on MRI-killed iPhones, we couldn’t imagine how poisoning a micro-electromechanical system (MEMS) part could kill a phone. We’d always associated MEMS with accelerometers and gyros, important sensors in the smartphone suite, but hardly essential. It turns out there’s another MEMS component in many Apple products: an SiT 1532 oscillator, a tiny replacement for quartz crystal oscillators.

[Ben] got a few from DigiKey and put them through some tests in a DIY gas chamber. He found that a partial pressure of helium as low as 2 kPa, or just 2% of atmospheric pressure, can kill the oscillator. To understand why, and because [Ben] has a scanning electron microscope, he lapped down some spare MEMS oscillators to expose their intricate innards. His SEM images are stunning but perplexing, raising questions about how such things could be made which he also addresses.

The bottom line: helium poisons MEMS oscillators in low enough concentrations that the original MRI story is plausible. As a bonus, we now understand MEMS devices a bit better, and have one more reason never to own an iPhone.

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The Electric Imp Sniffs Out California Wildfires

The wildfires in California are now officially the largest the state has ever seen. Over 50,000 people have been displaced from their homes, hundreds are missing, and the cost in property damage will surely be measured in the billions of dollars when all is said and done. With a disaster of this scale just the immediate effects are difficult to conceptualize, to say nothing of the collateral damage.

While not suggesting their situation is comparable to those who’ve lost their homes or families, Electric Imp CEO [Hugo Fiennes] has recently made a post on their blog calling attention to the air quality issues they’re seeing at their offices in Los Altos. To quantify the problem so that employees with respiratory issues would know the conditions before they came into work, they quickly hacked together a method for displaying particulate counts in their Slack server.

The key to the system is one of the laser particle sensors that we’re starting to see more of thanks to a fairly recent price drop on the technology. A small fan pulls air to be tested into the device, where a very sensitive optical sensor detects the light reflected by particles as they pass through the laser beam. The device reports not only how many particles are passing through it, but how large they are. The version of the sensor [Hugo] links to in his blog post includes an adapter board to make it easier to connect to your favorite microcontroller, but we’ve previously seen DIY builds which accomplish the same goal.

[Hugo] then goes on to provide firmware for the Electric Imp board that reads the current particulate counts from the sensor and creates a simple web page that can be viewed from anywhere in the world to see real-time conditions at the office. From there, this data can be plugged into a Slack webhook which will provide an instantaneous air quality reading anytime a user types “air” into the channel.

We’ve covered a number of air quality sensors over the years, and it doesn’t look like they’re going to become any less prevalent as time goes on. If anything, we’re seeing a trend towards networks of distributed pollution sensors so that citizens can collect their own data on their air they’re breathing.

[Thanks to DillonMCU for the tip.]

DIY Mini Helical Antennas From Salvaged Co-ax Cable

[Mare] has a visual guide and simple instructions for making DIY mini helical 868 MHz antennas for LoRa applications. 868 MHz is a license-free band in Europe, and this method yields a perfectly serviceable antenna that’s useful where space is constrained.

A metric 5 mm drill bit makes a convenient core.

The process is simple and well-documented, but as usual with antenna design it requires attention to detail. Wire for the antenna is silver-plated copper, salvaged from the core of RG214U coaxial cable. After straightening, the wire is wound tightly around a 5 mm core. 7 turns are each carefully spaced 2 mm apart. After that, it’s just a matter of measuring and bending the end for soldering to the wireless device in question. [Mare] has used this method for wireless LoRa sensors in space-constrained designs, and it also has the benefit of lowering part costs since it can be made and tested in-house.

Antennas have of course been made from far stranger things than salvaged wire; one of our favorites is this Yagi antenna made from segments of measuring tape.

A Candle Powered Guitar Pedal

When it comes to guitar effects pedals, the industry looks both back and forward in time. Back to the 50’s and 60’s when vacuum tubes and germanium transistors started to define the sound of the modern guitar, and forward as the expense and rarity of parts from decades ago becomes too expensive, to digital reproductions and effects. Rarely does an effects company look back to the turn of the 19th century for its technological innovations, but Zvex Effects’ “Mad Scientist,” [Zachary Vex], did just that when he created the Candela Vibrophase.

At the heart of the Candela is the lowly tea light. Available for next to nothing in bags of a hundred at your local Scandinavian furniture store, the tea light powers the Zvex pedal in three ways: First, the light from the candle powers the circuit by way of solar cells, second, the heat from the candle powers a Stirling engine, a heat engine which powers a rotating disk. This disc has a pattern on it which, when rotated, modifies the amount of light that reaches the third part of the engine – photoelectric cells. These modulate the input signal to create the effects that give the pedal its name, vibrato and phase.

Controls on the engine adjust the amount of the each effect. At one end, the effect is full phasor, at the other, full vibrato. In between a blend of the two. A ball magnet on a pivot is used to control the speed of the rotating disk by slowing the Stirling engine’s flywheel as it is moved closer.

While more of a work of art than a practical guitar effect, if you happen to be part of a steam punk inspired band, this might be right up your alley. For more information on Stirling engines, take a look at this post. Also take a look at this horizontal Stirling engine.

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A Hacked Solution For Non-Standard Audio Modules

When life hands you lemons, lemonade ends up being your drink of choice. When life hands you non-standard components, however, you’ve got little choice but to create your own standard to use them. Drinking lemonade in such a situation is left to your discretion.

The little audio record and playback modules [Fran Blanche] scored from eBay for a buck a piece are a good example. These widgets are chip-on-board devices that probably came from some toy manufacturer and can record and playback 20 seconds of audio with just a little external circuitry. [Fran] wants to record different clips on a bunch of these, and pictured using the card-edge connector provided to plug them the recording circuit. But the pad spacing didn’t fit any connector she could find, so she came up with her own. The module and a standard 0.1″ (2.54 mm) pitch header are both glued into a 3D-printed case, and the board is connected to the header by bonding wires. It makes a nice module that’s easily plugged in for recording, and as [Fran] points out, it’s pretty adorable to boot. Check it out in the video below.

Sure, the same thing could have been accomplished with a custom PCB breaking out the module’s pins to a standard card-edge connector. But [Fran] knows a thing or two about ordering PCBs, and our guess is she wanted to get this done with what was on hand rather than wait for weeks. There’s something to be said for semi-instant gratification, after all. And lemonade.

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