4-Bit Audio Output Via Voltage Reference

July 30, 2016 by 18 Comments

[Bruce Land] switched his microprocessor programming class over from Atmel parts to Microchip’s PIC32 series, and that means that he’s got a slightly different set of peripherals to play with. One thing that both chips lack, however is a digital-to-analog converter (DAC). Or do they? (Dun-dun-dun-duuuuhnnnn!)

The PIC part has a programmable, sixteen-level voltage reference. And what is a Vref if not a calibrated DAC? With that in mind, [Bruce] took to documenting its performance and starting to push it far beyond the manufacturer’s intentions. Turns out that the Vref has around 200 kHz of bandwidth. (Who would update a voltage reference 200,000 times per second?)

Anyway, [Bruce] being [Bruce], he noticed that the bits weren’t changing very often in anything more than the least significant bit: audio waveforms, sampled fast enough, are fairly continuous. This suggests using a differential PCM encoding, which knocks the bitrate down by 50% and saves a lot on storage. (Links to all the code for this experiment is inline with his writeup.)

The audio hacks that come out of [Bruce]’s Cornell ECE classes are always a treat. From the lock that you have to sing to open, to chiptunes programmed into an FPGA, there’s something for music fans of all inclinations.

Droolworthy Animatronic Stargate Horus Helmet

July 30, 2016 by 23 Comments

It’s incredibly likely that, unless you own one of the original movie props, your Stargate Horus helmet is not as cool as [jeromekelty]’s. We say this with some confidence because [jerome] got access to the original molds and put in an incredible amount of time on the animatronics. (See his latest video embedded below.)

Surprisingly, a number of the parts for this amazing piece were bought off the shelf. The irises that open and close they eyes, for instance, were bought on eBay. This is not to downplay the amount of custom design, though. The mechanism that moves the feathers is a sight to see, and there’s a lot of hand-machined metal holding it all together. But the payoff is watching the thing move under remote control. The eye dimming and closing, combined with the head movements, make it look almost alive.

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A Crash Sensor For Delta 3D Printers

July 30, 2016 by 4 Comments

It doesn’t happen that often, but this is the last time that [Lucas] comes back from hours of unattended 3D printing to find a large portion of plastic spaghetti mess and a partly disassembled Kossel. The crash sensor he designed will now safely halt the printer if it detects that something went wrong during the print.

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Hackaday Prize Entry: Reflectance Transformation Imaging

July 29, 2016 by 22 Comments

Reflectance transformation imaging (RTI), or polynomial texture mapping, is a very interesting imaging technique that allows you to capture all the detail of an object. It’s used to take finely detailed pictures of scrawlings on cave walls in archeology, capture every detail of a coin for coin collectors, and to measure the very slight changes in a work of art.

RTI does this by shining light over an object at very particular angles and then using image processing to produce the best image. Despite being only a few LEDs and a bit of software, RTI systems are outrageously expensive. For his Hackaday Prize entry, [leszekmp] is building his own RTI system. It’ll cost about $600, making this the best way for Citizen Scientists to capture the best image possible.

RTI is simply shining light onto an object and taking synchronized pictures of the object from directly above. As you can imagine, putting LEDs in a dome is the obvious solution to this problem, and already [leszekmp] has made three systems that works well on domes up to a meter in diameter. The electronics are as simple as an Arduino shield and a few MOSFETS, and the dome itself is an off the shelf component. It’s a great project that enables better photography, and one of the simplest and best entries we’ve seen for The Hackaday Prize.

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The Prettiest Darn Arcade Cabinet You’ll See Today

July 29, 2016 by 11 Comments

We see an awful lot of arcade cabinets around here, and so it’s pretty unusual for a build to get much more than a second glance. But, this beauty is just too good not to mention. The entire build, named “Ready Player One” as a nod to the engrossing Ernest Cline novel, is detailed in [scoodidabop’s] post on Reddit.

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A One LED Clock

July 29, 2016 by 18 Comments

Esoteric clocks are something of a staple among hardware hacker projects. If it can be made to tell the time correctly, even if only twice a day, the chances are someone’s made a clock from it. And if the only person who can read that clock is its creator, so much the better. Universal accessibility is not always a virtue in the world of unusual timepieces.

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[Setvir] writes to us with details of his One LED Clock. It’s an Arduino Pro Micro with an RTC module and an LED. That’s all, time is communicated to the world through LED flashes. You might expect therefore that it would use Morse Code, but he’s come up with his own timing communication scheme which does have some merit. Long flashes cover a quarter of the clock face, while short flashes cover individual hours or five-minute segments. He goes into detail on the project page and we can see that once you are used to the scheme it has an elegance to it, but it certainly ticks the essential unreadable-to-the-uninitiated box for an esoteric clock.

We like it though for its simplicity and for the flashing scheme, which once explained is both efficient and easy to read. If you would like to have a go yourself he’s published his code, so go forth and cover the world with baffling single-LED timepieces!

We’ve featured a few minimalist LED clocks before, at least one with a minimal face, and another single-LED offering. But that one used a bi-colour LED, so [Setvir] takes the minimalism crown.

Fail Of The Week: Magnetic Flow Measurement Gone Wrong

July 29, 2016 by 42 Comments

Physics gives us the basic tools needed to understand the universe, but turning theory into something useful is how engineers make their living. Pushing on that boundary is the subject of this week’s Fail of the Week, wherein we follow the travails of making a working magnetic flowmeter (YouTube, embedded below).

Theory suggests that measuring fluid flow should be simple. After all, sticking a magnetic paddle wheel into a fluid stream and counting pulses with a reed switch or Hall sensor is pretty straightforward, right? In this case, though, [Grady] of Practical Engineering starts out with a much more complicated flow measurement modality – electromagnetic detection. He does a great job of explaining Faraday’s Law of Induction and how a fluid can be the conductor that moves through a magnetic field and has a measurable current induced in it. The current should be proportional to the velocity of the fluid, so it should be a snap to whip up a homebrew magnetic flowmeter, right? Nope – despite valiant effort, [Grady] was never able to get a usable signal out of the noise in his system. 

The theory is sound, his test rig looks workable, and he’s got some pretty decent instrumentation. So where did [Grady] go wrong? Could he clean up the signal with a better instrumentation amp? What would happen if he changed the process fluid to something more conductive, like salt water? By his own admission, electrical engineering is not his strong suit – he’s a civil engineer by trade. Think you can clean up that signal? Let us know in the comments section. 

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