Riding rockets and jets around the frozen wastes of Sweden

An attentive reader tipped us off to the guys at Mobacken Racing (translation), a group of Swedes dedicated to the art and craft of putting jet and rocket engines on go karts and snowmobiles.

One of the simpler builds is a pulse jet sled. Pulse jets are extremely simple devices – just a few stainless steel tubes welded together and started with a leaf blower. The simplicity of a pulse jet lends itself to running very hot and very loudly; the perfect engine for putting the fear of a Norse god into the hearts of racing opponents.

Pulse jets are a bit too simple for [Johansson], so he dedicates his time towards building a jet turbine engine. Right now it’s only on a test stand, but there’s still an awesome amount of thrust coming out of that thing, as shown in the video after the break.

In our humble opinion, the most interesting build is the 1000 Newton liquid fuel rocket engine. The liquid-cooled engine guzzles NOX and methanol, and bears a striking resemblance to liquid fuel engines we’ve seen before. Sadly, there are no videos of this engine being fired (only pics of it strapped to a go-kart), but sit back and watch a couple other hilariously overpowered engines disturbing a tranquil sylvan winter after the break.

Edit: [Linus Nilsson] wrote in to tell us while the guys at Mobacken Racing are good friends, [Linus], his brother, and third guy (his words) are responsible for the pulse jet sled. The pulse jet is actually ‘valved’ and not as simple as a few stainless steel tubes. The pulse jet isn’t started by a leaf blower, either, but a four kilowatt fan. [Linus]‘ crew call themselves Svarthalet racing, and you can check out the Google translation here.

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Piano Box is a digital synthesizer made of paper

We love the look of this papercraft piano which [Catarina] built along with some friends at NYC Resistor, a hackerspace in the big apple. It starts off as a cubic black box with a white top. But just lift that top as [Catarina] does in the video after the break and three of the sides fall flat to reveal a pair of speakers and the single-octave keyboard.

The key’s don’t move when you press them. Instead, she decided to use the CapSense Arduino library to implement touch sensitive keys. Each key is made up of a plane of copper foil tape, with a strip of tape running back to the center of the box where it is interfaced with an Arduino Mega hidden there. The Tone library produces the waveforms which are played by the speakers, and a set of LEDs on the upright side of the box illuminate the keyboard diagram as you press each key. You can see that there are short white bars on that display which correspond to the black keys on the keyboard.

If you take a look at the code, you’ll see the libraries really make the code for the project simple.

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Polish your understanding of capacitors by building this meter

Building a capacitance meter is a great exercise. If you’re feeling quite safe in your digital-circuit-only life, this will push just far enough out of the comfort zone for you to see there’s nothing to fear in adding analog circuits to your designs. Here, [Raj] compares a voltage divider and RC timer to calculate the value of a capacitor. The project is aimed at teaching the concepts, and will be easy to follow for anyone who has at least a bit of experience working with a programmable microcontroller.

The meter is based on an established equation that uses are starting and ending voltage, as well as the time it took to transition between the two, to calculate capacitance. The capacitor will be charged from 0 volts to 0.5 volts. Using the built-in analog comparator is the easiest way to do this. [Raj] breadboarded a voltage divider to establish a 0.5V reference on one of the comparator’s pins. The other input comes from a circuit that places a resistor in line with the capacitor being tested. When that reading rises above the 0.5 volt reference the comparator match will be tripped, stopping a timer that had been running during the charge cycle. From there it’s just a matter of using the timer value in the calculation.

Resurrecting a cellphone with blown USB circuitry

[Script] is pretty lucky. One of the engineers who designed his cellphone included over-voltage protection in the circuit. Of course you probably wouldn’t know about this if there wasn’t a service schematic available. But a bit of searching around let him resurrect the fried USB segment of his Nokia N900.

Now [Script] has been experimenting with portable solar power like the system featured at 25C3 a few years back. Unfortunately he made an error which routed 12V into the USB connector’s 5V rail. After this unfortunate mistake the phone would not longer connect via USB, or charge the battery. Luickly the N900 is a favorite with the hacker community (you can see all kinds of N900 related projects here at Hackaday) and [Script] found his way to their N900 Schematic page. Digging into page four he found part F5300 which is labeled 2.0A. He removed the PCB and shielding, and tested the part with a multimeter to confirm it was blown. A quick wire bridge got the phone charging again, but [Script] plans to position a new fuse as soon as he can source the part.

Who says these devices aren’t user serviceable? If we could just get our hands on more service schematics perhaps our gear would last longer.

Collecting Radon data in the name of science and safety

radon-data-collector

When [Chris Nafis] built an addition onto his historical home he found that a Radon problem, previously mitigated with plenty of concrete, seemed to rear its ugly head yet again. He eventually resigned himself to installing a Radon fan and detector – the latter of which offered no way to store measurement data. He wanted to get a better feel for the short and long-term Radon measurements in his house, in hopes of finding some correlation between temperature, moisture levels, and the total amount of Radon emitted from the ground.

To do this, he disassembled a pair of Radon detectors located in different parts of his house, each of which he wired up to an Arduino. Using his oscilloscope to determine which PCB leads controlled the different LED segments on the displays, he quickly had the Arduinos scraping measurement data from the sensors. [Chris] figured the best way to keep track of his data was to do it online, so he interfaced the microcontrollers with Pachube, where he can easily analyze his historical readings.

An additional goal he set for himself is to trigger the Radon fan only when levels start rising in order to save a little on his electric bill. With his data logging operation in full swing, we think it should be a easy task to accomplish.

Building an artificial heart with ferrofluids

Here’s something we thought we’d never see on Hackaday. [Chris Suprock] is developing an artificial heart he calls Steel Heart. It’s an artificial heart powered by electromagnets and ferrofluids.

The idea behind [Chris]‘ artificial heart is ingenious in its simplicity. An elastic membrane is stretched across a frame and a magnetic liquid (or ferrofluid, if you prefer) is poured across the membrane. An electromagnet is activated and the membrane stretches out, simulating the beating of a heart. Put a few of these together and you’ve got a compact, biologically inert pump that’s perfect for replacing an aging ticker.

[Chris]‘ plan to use ferrofluids and electromagnets as an artificial heart give us pause to actually think about what he’s done here. Previously, artificial hearts used either pneumatics or motors to pump blood throughout the body. Pneumatic pumps required plastic tubes coming out of the body – not a satisfactory long-term solution. Motor-driven pumps can rupture red blood cells leading to hemolysis. Using ferrofluids and an elastic membrane allows for the best of both worlds – undamaged blood cells and transdermal induction charging.

Not only is [Chris] designing a freaking artificial heart, he also came up with a useful application of ferrofluids. We were nearly ready to write off magnetic particles suspended in a liquid as a cool science toy or artistic inspiration. You can check out [Chris]‘ indiegogo video with a demo of the ferrofluid pump in action after the break.

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[Aaron] shows us what life would be like if [Bob Vila] started hacking headphones

construction-headphones

[Aaron Horeth] had a pair of headphones that had seen better days, and before he tossed them out, he realized that he could use them to build a set of custom cans. He had always wanted a pair of headphones with a detachable cord to prevent damage when tripped over, and thought that his old set would be the perfect donor.

He swung by his local hardware store to peruse their collection of construction earmuffs, eventually finding a set that looked decent and didn’t cost an arm and a leg. Using construction earmuffs as the framework for his headphones gave him the durability he was looking for with the added bonus of being designed to deaden extraneous noise. Once he got them home he pulled the drivers from his old set of headphones installing them into the earmuffs, but not before he wired them up to support a breakaway input cable.

There’s no doubt that the modifications are simple, but we imagine they come in pretty handy when tinkering around the shop.

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