Making S’mores With 50,000 Volts

August 26, 2013 by Eric Evenchick 12 Comments

[Skyy] sent us a video of him cooking s’mores with an electric arc. He’s using a flyback transformer with a zero voltage switching (ZVS) driver. This produces about 50 kV, which is more than enough to toast the marshmallow.

ZVS is a technique that triggers the semiconductor switches when they have zero voltage across them. This ensures that there’s minimal heat created by the switches, since they are not interrupting any current at the time they are toggled. ZVS is also used in lighting dimmers to switch off power without creating interference.

If you’re interested in the details, there’s a great tutorial on building the driver. If you’re interested in learning how it works, check out this simulation video.

[Skyy] admits that his setup isn’t terribly safe since it uses a breadboard, which isn’t rated for the high voltages and currents. Keep in mind that these circuits could kill you. After the break, watch a marshmallow fry in a 50 kV arc.

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Building An Ethernet Connected RFID Reader

August 26, 2013 by Mathieu Stephan 14 Comments

For the last few years, [Lt_Lemming] was the president of Brisbane’s hackerspace. Until several months ago, access to the local was done using 125KHz RFID tags and an Arduino board with a prototyping shield. As the hackerspace gained members and moved to bigger facilities, [Lt_Lemming] decided to build himself a more compact and advanced platform.

His Simple NetworkAble RFID Controller (SNARC) is a platform which can be connected to an Ethernet network and different RFID readers in order to implement smart access control functionalities. Through hole components were selected so even solder apprentices may assemble it. The PCB was designed using Fritzing, and development can even be done inside the Arduino IDE as ISP and serial headers are available on the board. Finally, an N-channel mosfet controls the door locking mechanism.

The project is open hardware and software, and all the sources can be downloaded from [Lt_Lemming]’s github repo.

[Update] Vladimir’s Robot Guitar

August 26, 2013 by Marsh 24 Comments

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[Vladimir Demin] is somewhat of a legend for us; in his spare time he’s been mastering the automation of musical instruments. This time he’s back with upgrades to his build and four new videos. [Vladimir’s] top priority was to rework the strumming mechanism that earlier ran on solenoids. He’s improved the sound quality and reduced the clicks by swapped to stepper motors and overhauling the software.

Compared to his earlier setup, this one sounds more soulful and less automated, but [Vladimir] admits that it’s still not good enough and that he’s working on a new, brilliant implementation. Until then, take a few minutes and check out the rest of the videos below, then join us in scratching our heads in amazement: everything is built with simple hand tools.

[Vladimir] has come a long way, and it started with this Bayan (button accordion). Last year’s guitar build is also worth a look, as well as an in-depth interview.

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Logging Two Multimeters At (nearly) The Same Time

August 26, 2013 by Mike Szczys 13 Comments

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It’s pretty common to have at least a couple of meters around to measure different values of a circuit at the same time. Where [Emilio P.G. Ficara] ran into a problem was logging the data from both at once. These ~~Fluke~~ meters have a serial-out, but his computer only has a single serial-in port. He cracked open one of the meters and figured out how to log data from both at the same time.

A lot of folks would look to a microcontroller to solve this problem. You use the chip to pull from each meter simultaneously and report back to a computer (or just dump the values onto an SD card). But this solution is a simple mechanical connector and a bit of creative programming. The way the serial output is set up on these meters they won’t interfere with each other as long as they’re read one at a time. [Emilio] wired them up as seen above, using his own software to manage the pins of the serial port. The example output he posted shows readings from the meters taken within about a tenth of second from each other. That should be good enough for most applications.

Reaction Time Challenge

August 26, 2013 by Marsh 3 Comments

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We’re not sure where [Bill Porter] finds all of his free time, but we’re glad he’s put it to such good use by building an exhibit piece for the local science museum: Reaction Time Challenge. It’s likely that we were all inspired to love science as kids in a museum like this, and [Bill’s] contribution is already fascinating its young audience. The challenge lets two participants test how fast they can smack a big red button after a randomly-generated countdown. The time taken for the players to react is translated into the RGB LED strips, measuring how fast they managed to hit the button.

Builds like this one need to clearly communicate how they should be used; you don’t want confused children bamming around on your cabinet. First, [Bill] guts the dim LEDs inside the big plastic buttons and replaces them with some brighter ones. To keep the connections clean, he takes the cannibalized ends of an Ethernet cable and hooks the speaker and buttons to an Ethernet jack. The jack sits snugly in a project box where it connects to an Arduino. Two RGB LED strips run from the opposite end of the box, daisy-chaining from the bottom of the cabinet to the top, then back down again. See it all come together in the video after the break.

[Bill’s] museum must be pretty lucky; he resurrected the “Freeze Frame” exhibit for them just over a year ago and has done a bunch of other projects for them over the years.

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Hackaday Links: August 25, 2013

August 25, 2013 by Mike Szczys 24 Comments

[Adrian] came across a treasure trove of 507 mechanical device designs. It didn’t seem quite right for a Retrotechtacular post, but we wanted to share it as it’s a great place to come up with ideas for your next Rube Goldberg machine.

Biking with headphones is dangerous. That’s why [J.R.] built a handlebar enclosure for his Jambox Bluetooth speaker.

While dumpster diving [Mike] found a Macbook pro. It was missing a few things, like a keyboard, touchpad, battery, ram, and storage. He borrowed a power supply to test it out but without the keyboard there’s no power button. He figured out the traces on the motherboard which turn it on when shorted.

[Mateusz] want to let us know about the Hercules LaunchPad. Like the other TI Launchpad offerings it’s an all-in-one dev board. The Hercules line features a couple of flavors of dual-core ARM chips. Can you believe the dev boards you can get for under $20 these days?

After seeing the ammo can sound system about a month ago [Ilpo] was inspired to share his ammo can PC case with us.

And finally, here’s a way to display your Bitcoin mining rig for all to see. This system was laid out in an antique frame and hung on the wall.

The Difference Between Bitcrushers And Sample Rate Reducers

August 25, 2013 by Brian Benchoff 23 Comments

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If you look around a few electronic music forums, you’ll see a lot of confusion over the difference between a bitcrusher – a filter that reduces the bit depth of an audio signal – and a sample rate reducer – a filter that does exactly what its name implies. With the popularization of 8-bit and retro synth music, this difference is obviously of grave import of concern to saints and kings alike. [Michael] is more than happy to walk us through the difference with real-time sample and bit rate adjustment with his audio hacker board.

The audio hacker board is an Arduino shield with a 12-bit DAC and a 12-bit ADC. With two 1/8″ jacks and a pair of pots, [Michael] was easily able to whip up a sketch that is able to adjust the sample rate and bit depth of an audio signal in real-time.

Contrary to nearly everyone’s opinion of what ‘8-bit’ music is, it’s actually the sample rate that makes music sound like a cassette deck jury rigged into a Nintendo Entertainment System. Reducing the bitrate just makes any audio source sound louder and worse.

Check out the excellent demo video of the effect of bitcrushers and sample rate reducers below.

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