Building A Combination Lock With Logic Chips

March 30, 2012 by Brian Benchoff 10 Comments

The component gods must have smiled on [Darrell], because he recently ran into a cabinet full of 7400-series logic chips for sale at his local college surplus. All the regulars were there – flip-flops, logic gates, and SRAMs – in DIP packages. the 7400-series of logic chips gets very esoteric as the numbers increased, so when [Darrell] found a 74ALS679 address comparator, he didn’t quite realize what he had. After a quick review of the relevant datasheet he had a fairly good idea of the actual function of this chip and decided to make a combination lock.

From the datasheet, [Darrell] figured out how this small logic chip can compare two 12-bit addresses with only 20 pins: each of the 12 address pins are hardwired to match a single four-bit value. If the four-bit ‘key’ is set to 0110, the first six address pins are tied low, and pins 7-12 are tied high. After wiring up his address comparator to a trio of Hex dip switches, [Darrell] had a combination lock that used the word ‘FAB’ as a key.

In the 7400-series of logic chips, there are some oddballs; the 7447 seven-segment display driver is useful, but the 74881 ALU and 74361 bubble memory timing generator aren’t exactly something you would find in a random component stash. If you’ve got a weird logic chip build (there’s a 300-baud modem, you know), send it on in. You can check out an animated gif of [Darrell]’s lock after the break.

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Grabbing Data From A Rigol ‘scope With Python

March 30, 2012 by Brian Benchoff 13 Comments

While a fancy Rigol 1052E oscilloscope is a great tool and a wonderful portable oscilloscope we heartily recommend, sometimes you just need to use the more ‘advanced’ functions of an oscilloscope. Luckily, [cibomahto] figured out how to use a Rigol scope with Python, allowing for easy remote viewing and control of a Rigol 1052E ‘scope on any desktop computer.

[cibomahto]’s Python script grabs the screen and can send commands to the oscilloscope, effectively obviating the need for the slightly-terrible Rigol Ultrascope software. Not only that, controlling the 1052E is possible under OS X and Linux because of the portable Python nature of [cibomahto]’s work.

The Rigol DS1052E has become the de facto standard oscilloscope to grace the workbenches of makers and hackers around the globe. With a small price tag, the ability to double the bandwidth, and an active homebrew development scene, we doubt [cibomahto]’s work of grabbing data over USB will be the last hack we’ll see for this fine machine.

Thanks to [Markus] for sending this one in.

Working Software-defined Radio With A TV Tuner Card.

March 30, 2012 by Brian Benchoff 77 Comments

[Balint Seeber] just sent in a small yet timely project he’s been working on: a software radio source block for the Realtek RTL2832U. Now with a cheap USB TV tuner card, you can jump right into the world of software-defined radio.

[Balint]’s code comes just a week after hackaday and other outlets posted stories about using a $20 USB TV capture dongle for software defined radio. At the time, these capture cards could only write data directly to a file. With [Balint]’s work, anyone can use a cheap tv tuner dongle with HDSDR, Winrad, or GNU Radio. If you’ve ever thought about trying out software-defined radio, now might be the time.

Elsewhere on the Internet, a surprisingly active RTL-SDR subreddit popped up dedicated to using the Realtek RTL2832U tuner for software defined radio. There’s an awesome compatibility chart listing compatible USB dongles. The cheapest (so far, and subject to change) is the Unikoo UK001T available for $11 on eBay.

With his source block, [Balint] can listen to anything on the radio between 64-1700 MHz. The sample depth is 8 bits and the sample rate can be anything up to 3.2 MHz. You can watch [Balint] testing out his $20 GNU Radio rig after the break.

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Ask Hackaday: Building Nano Scale Antennas

March 28, 2012 by Brian Benchoff 70 Comments

As an RF engineering student, [Camerin] is usually tasked with pointless yet educational endeavors by his advisor and professors. Most of the time (we hope) he sees the task through and ends up pulling something out of his hat, but a few days ago a professor dropped a bombshell on him. After reading this article on nano scale antenna fabrication, a professor asked [Camerin] if it was possible to build a 3D inkjet printer with a ludicrous amount of accuracy and precision.

The full article, Conformal Printing of Electrically Small Antennas on Three-Dimensional Surfaces, was recently published in Advanced Materials and is available via Google Scholar. The jist of the article is that three-dimensional antennas printed on a sphere approach the physical limits of how good an antenna can be. To test out these small, spherical antennas, the authors of the paper built an extremely high-precision 3D inkjet printer that draws antenna traces on a glass sphere with conductive ink.

The positional accuracy of this printer is 50 nanometers, or about half the size of an HIV virus. The conductive silver ink is delivered by a nozzle with a diameter of 100 to 30 µm and prints onto a glass sphere about 6 mm in diameter. This is a level of precision that companies and research institutions pay top dollar for, so we’re left wondering how the authors built this thing.

We’re turning this question over to the astute readers of Hackaday: how exactly would you build a 3D inkjet printer with this much accuracy and precision? Would it even need to be that precise? Post your answer in the comments.

Building The Worst Linux PC Ever

March 28, 2012 by Brian Benchoff 124 Comments

Linux is generally considered the go-to OS for under powered computers. Wanting to challenge the preconceived notion that Linux requires ‘a computer made in the last 20 years,’ [Dmitry] built the worst Linux PC ever around a simple 8-bit microcontroller.

The ATMega1284p [Dmitry] used doesn’t have a lot to offer as far as RAM and storage goes; just 16 kilobytes of SRAM and a paltry 128 kilobytes of Flash storage. While this may be voluminous in the embedded world, it’s peanuts compared to the gigabytes of RAM and hard drive space on even a low-end netbook. To solve this problem, [Dmitry] threw an antique 30-pin RAM SIMM at the problem. It’s wired up directly to the microcontroller, as is the 1 Gigabyte SD card that serves as the PC’s hard drive.

Linux requires a 32-bit CPU and a memory management unit, something the puny microcontroller doesn’t have. For [Dmitry], the best course of action was emulating an ARM processor on an AVR. We’re not sure if we’re dealing with genius or madness here, but it did prove to be a valuable learning exercise in writing a modular ARM emulator.

How fast is it? [Dmitry] tells us it takes two hours to boot up to a bash prompt, and four more to load up Ubuntu and login. If you want a Megahertz rating, good luck; the effective clock speed is about 6.5 kilohertz. While the worst Linux PC ever won’t win any races, its simple construction puts it within the reach of even the klutziest of hardware builders; the entire device is just a microcontroller, RAM, SD card, a few resistors, and some wire.

If you’d like to build your own worst Linux PC, [Dmitry] has the firmware and disk image available to download. If you want to watch the ~~time-lapse~~ of this thing booting, check out the video after the break.

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Riding Rockets And Jets Around The Frozen Wastes Of Sweden

March 27, 2012 by Brian Benchoff 31 Comments

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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Building An Artificial Heart With Ferrofluids

March 27, 2012 by Brian Benchoff 61 Comments

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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