[Staci Elaan]’s Awesome Portable Tesla Coils.

December 8, 2012 by Caleb Kraft 45 Comments

We stumbled onto [Staci’s] videos a while ago when we posted this big tesla gun. While it wasn’t the first portable coil we had seen, it was certainly an impressive implementation. In the comments we found [Staci] had already been making these for a while. Hers were big and small, had awesome modulation, and looked freaking cool too.

It also should be pointed out that [Staci] donates her coils to people when she’s done! Let me say that again, she gives them away to groups of people that could use them. That deserves some respect.

Unfortunately, [Staci] didn’t document her builds in great detail at the time. She has added some information recently though. You can read about her first working prototype from 2006, or a slightly more modern one here.

Of course, the real fun is in seeing them work.

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An Introduction To Vector Displays

December 5, 2012 by Brian Benchoff 20 Comments

Unlike the CRTs found in big old televisions, vector displays are a bit of a historical oddity. Instead of sweeping an electron beam across the screen from left to right and top to bottom, a vector display draws lines between two points on a screen. Once used in arcade games such as Asteroids, Tempest, and old FAA displays, vector monitors have fallen out of favor due to either the complexity or difficulty in acquiring the needed CRT. The folks over at NYC Resistor put up a great tutorial for getting a vector display up and running, and even managed to put a clock on an oscilloscope.

The key component of getting a vector display to work is the digital to analog converter. This DAC takes voltages from eight pins on a Teensy 2.0 dev board and converts them to a voltage anywhere in between 0 and 5 Volts. After connecting the output of this DAC to an input on an oscilloscope, the microcontroller can draw a line between any two points on an axis.

In the video after the break, you can see two of these DACs connected to an oscilloscope displaying a clock. It’s a very cool piece of work, and something that finally gives a purpose to the ancient CRT oscilloscope you might have lying around.

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Cute Little Amplifier Has A Tube Pre

December 4, 2012 by Brian Benchoff 64 Comments

tube

While you won’t catch us in an argument with an audiophile regarding the sound quality of tube vs. solid state amps, there is a general consensus that tube amplifiers sound much better than their transistorized brethren. Actually building an all-tube amplifier, though, is a bit harder than one built around common ICs – there are transformers to deal with and of course very high voltages. One solution to get the sound of tubes easily but still retaining the simplicity of integrated circuits is a hybrid amp, or a tube preamplifier combined with a solid state power section. They’re easy enough to build as [Danilo] shows us with his hybrid tube amp design (Italian, translation).

[Danilo]’s design uses two ECC86 for the left and right channels powered by a 12 Volt supply. Each channel is sent through a tube and then amplified by a TDA2005 20 Watt power amplifier. After plugging in a CD player, the result is a clear, warm sound that can put a whole lot of power through a speaker.

Teaching The Speak & Spell Four (and More) Letter Words

December 3, 2012 by Brian Benchoff 27 Comments

Before it became the darling of circuit benders the world over, the Speak & Spell was a marvel of modern technology. Complete with a microprocessor and voice synthesizer, the Speak & Spell was able to speak a limited vocabulary that [Furrtek] thought should include words such as, “al qaeda”, “necrosis”, and “butt”. The Speak & Spell included an expansion port for cartridges containing a larger vocabulary, and with a huge amount of effort [Furrtek] created his own Speak & Spell carts that allow it to talk like a sailor.

The Speak & Spell ROMs were stored on a very strange memory chip; instead of a parallel or serial interface, the chip reads five nybbles at a time before returning the saved data. At first, [Furrtek] thought he could get an ATtiny microcontroller, but the way this memory chip is set up made it impossible to send and receive data even on a 400kHz I2C bus.

The project eventually found some decent hardware in the form of a CPLD-based cartridge that was more than fast enough to interface with the Speak & Spell. After that, it was only an issue of converting words into something the speech synth can understand with some old Windows 3.1 software and finally burning a ROM.

The end result is a Speak & Spell with a perverse vocabulary and is much, much more interesting than a circuit bent piece of hardware with a few wires crossed. Check out the video after the break.

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Tiny MAME Cabinet Built From Raspberry Pi

November 26, 2012 by Brian Benchoff 17 Comments

It’s been a while since we’ve seen [Sprite_tm] pull a project from thin air, and we haven’t seen him do anything with a Raspberry Pi yet. All things must pass, and finally [Sprite] has unleashed his tiny, pocket-sized MAME machine to the world.

The build uses a Raspi for all the Linux-ey and MAME goodness, but [Sprite_tm] didn’t want to fiddle around with the HDMI or analog video output. Instead, he chose to use an SPI-controlled TFT display that is only 2.4 inches across. This isn’t a new hack for [Sprite] – he figured out how to connect this display over GPIO pins with a Carambola earlier this year.

To make his cabinet portable, [Sprite] opted for using old cell phone batteries with a cleverly designed charging circuit. When the power supply is connected to +5V, the batteries charge. When this power is removed, an ATtiny85 provides 5V of power to the Raspi and display.

No arcade cabinet is complete without a marquee of some sort, so [Sprite] used an extremely tiny 128×32 white OLED to display the logo of the game currently being played. Everything in the Raspi is set up to be completely seamless when switching between games, automatically configuring the controls and marquee for the currently selected game.

You can check out [Sprite]’s mini MAME booting straight into Bubble Bobble after the break along with some gameplay footage and finally switching it over to Nemesis. A very awesome build from an exceedingly awesome maker.

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Playing Led Zeppelin On A C64

November 14, 2012 by Brian Benchoff 24 Comments

[youtube=http://www.youtube.com/watch?v=Iikj5EfL770&w=470]

In the C64 demoscene there are a ton of awesome software hacks that push the Commodore 64, the 1MHz 6510-based computer from 1982, to its limits. Most of these C64 demos are very much limited by the hardware inside the C64, but the demoscene is always coming up with new ways of pushing the envelope. [No Quarter] just sent in one of these software hacks that propel the capabilities of the C64 into the realm of absurdity by playing full length songs directly from the floppy drive.

Playing a song on the C64 begins with an Amiga and a Perfect Sound digitizer to convert the digital audio file into a 4-bit sample. Once this sample is transferred over to the C64 where it was manually timed so streaming it off a 1581 disk drive would result in the song playing at the correct pitch. It’s an amazing work of optimization; the audio data is streamed off the disk just as fast as it’s played from memory, an amazing data throughput rate for the ‘ol C64

After the break you can see [No Quarter] playing Led Zeppelin, Bon Jovi, Shania Twain, and Extreme. A very, very cool project and with the addition of a C64 hard drive makes it possible to have a media player for the C64.
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Storing 32 Bits Of Data In A Piece Of Glass

November 9, 2012 by Brian Benchoff 35 Comments

After finding an old piezoelectric delay line in an old TV, [Mike] decided to figure out how it works and in the process stored his name in sound waves reflecting inside a piece of glass

[Mike] was intrigued by these old-fashioned delay lines after watching [Dave] from EEVblog’s teardown of an circa 1985 camcorder. [Dave] found a piezoelectric delay line in his camcorder – a device that is able to store digital data by sending a sound wave into a glass plate, letting the sound wave bounce through the plate. and picking up the sound on the other end. It’s actually not too dissimilar to a mercury delay line used in the earliest computers.

After sending a pulse through his piezoelectric delay line, [Mike] picked up an echo almost exactly 64 microseconds later. After hooking up a simple circuit constructed out of a 74-series chip, [Mike] found he could ‘loop’ the delay line and keep a pulse going for up to 3 milliseconds.

Three milliseconds isn’t much, but by injecting serial data into the delay line, [Mike] was able to spell out his name in binary, as seen above. It’s just 32 bits stored for a fraction of a second, making it a very volatile, low-capacity memory, but functionally equivalent to the old mercury delay lines of yore.

It’s certainly not what [Mike] or [Dave]’s delay line was designed to do; these video delay lines were used to hold the previous line of video for a form of error correction. Outside [Mike]’s workbench and a few museums, though, you won’t see a delay line used as a form of computer memory. A very cool build and an awesome history lesson, and we thank [Mike] for that.