Controlling Shift Registers Via SPI

November 5, 2011 by Brian Benchoff 12 Comments

Hack a Day’s very own (and very prolific contributor) [Mike Szczys] put up a great tutorial on how to drive shift registers with an SPI interface.

[Mike]’s earlier tutorial of the 595 shift register goes through the functions of a shift register pin by pin. In a 595, bits for each position in the register are sent over one at a time. Most microprocessors have an Serial Peripheral Interface, and using an SPI bus means a lot less mucking about.

An ATmega168 was used for this build, although most Atmel chips can be made to work as an SPI master device. There are just three wires connecting the microcontroller to the shift register – SER, SRCLK, and RCLK. Like any other shift register setup, the build can be expanded by connecting the QH’ pin of the first 595 to the SER pin of the second.

[Mike] graciously made all the code for his build available. The video after the break is a 16-bit binary counter, a good stopping point before [Mike] rebuilds his Larson scanner/Cylon/Kitt, moving away from a PWM-based build to a register-based one.

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LED Sexting Belt Buckle

November 1, 2011 by Brian Benchoff 11 Comments

For some ungodly reason, [Scott] has a friend that wanted a ‘sexting themed’ Halloween costume. We won’t try to make any presumptions of the creativity or mental stability of [Scott]’s friend, but the SMS scrolling LED belt buckle he came up with is pretty cool.

The belt is based around a $13 scrolling LED belt buckle [Scott] found online. There was a problem with the belt buckle, though. Thirteen dollars means [Scott] didn’t get a whole lot of features with his buckle, so there are only 3 buttons on the entire device: letter up, letter down, and enter. Instead of pressing a button 80 times to get a lowercase ‘z,’ an Arduino was thrown into the mix to take care of all the button pressing.

The Arduino sketch could now input any message into the belt buckle in a matter of seconds. All that was left to do is taking care of the SMS to text part of the build. For this, [Scott] used the Sparkfun USB Host Shield and a custom Android app. Whenever an SMS is received on the phone, the message is sent through the USB shield to the Arduino and output on the belt buckle.

We won’t make any assumptions about the content of the messages during the Halloween party, but at least the video demo of the build is family friendly. Check it out after the break.

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Turning LEDs Into A Camera

November 1, 2011 by Brian Benchoff 17 Comments

[Udo] figured out how to turn a bunch of LEDs into a very low resolution camera.

The build is based around [Udo]’s Blinkenlight shield he’s been developing over the past year. The camera operates under the idea that there’s really not much difference between a LED and a photodiode; LEDs can do light emission and detection. In actuality, the LED ‘camera’ isn’t all that different from a linear CCD array, the type of image sensor in flatbed scanners.

After connecting his Blinkenlight shield to his Arduino and computer, [Udo] wrote a sketch that would capture 17 values from his LED camera. These values are shot over the serial connection where high levels of light show up as smaller numbers and low light levels are understood as larger numbers.

[Udo] has been doing a lot of other cool stuff with his Blinkenlight shield, like a persistence of vision experiment and pretending to be [Michael Knight]. Check out the video after the break for a demo of [Udo]’s linear LED camera.

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Wine-o-Meter Quantifies Your Bachelor Party Bad Behavior

October 31, 2011 by Mike Nathan 6 Comments

wine_o_meter

[Phil] had a bunch of Shiftbrite modules set aside for an LED table project, but before he could get around to it, he decided to use them to build a prop for his friend’s bachelor party. Expecting plenty of drunken revelry, he constructed the Arduino Wine-o-Meter – a carnival “Test your strength” style breathalyzer.

The 25 Shiftbrite modules are lined up in a column, which is connected to an Arduino tucked away in a cardboard box. The Arduino takes readings from an MQ-3 Gas/Alcohol sensor was salvaged from another breathalyzer build [Phil] put together. While it has been noted in the past that this sensor is pretty inaccurate, it seems to serve his purposes quite well. Since his game is based on measuring the players’ blood alcohol content in relation to one another rather than obtaining an exact BAC reading, the poor calibration of the device should affect everyone equally.

It looks pretty cool, and we imagine that it will ensure that the party stays lively throughout the wee hours of the night. Check out the video below to see [Phil] walk you through a demo of his Wine-o-Meter.

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Old-school Projector Turned Digital

October 31, 2011 by Brian Benchoff 21 Comments

Who hasn’t thought about turning a 1950s slide projector into a digital projector? [Matt] did, but unlike most of us, he actually did it.

[Matt]’s friend [Angus] found an old, single-slide, sans-carousel slide projector in the trash. It’s a wonderful piece of ancient technology with a fabric insulated power cord and bakelite lamp socket. This projector was upcycled to the 21st century by adding a 10 Watt LED and a Nokia 1200 LCD.

For the electronics, [Matt] used an ATmega88 microcontroller. There’s an infrared receiver so the remote from an in-car CD player can be used to advance the slides and turn the projector on and off. The LCD is controlled by a bit of bit-banging from the Mega88, using hard-coded images of Che Guevara, Hendrix, Space Invaders and some old-school Macintosh/Lisa icons. Unlike the screen printed t-shirts at American Apparel, Che is the only authentic image in this project; this projector might have been made after Guevara came to prominence.

With a 10 Watt LED, it’s not the brightest projector on the planet and the picture is a little washed out in a bright room. With dim lighting, it’s a very good project even if the images are static.

Detailed Tutorial Shows How To Unleash Your Inner [Michael Knight]

October 28, 2011 by Mike Nathan 12 Comments

developing_a_larson_scanner

Our own [Mike Szczys] recently sat down and put together a great tutorial on building a Larson Scanner. The ubiquitous circuit is usually one of the first few projects on a budding hackers list of things to build, since they are just so darn fun.

Simple versions of the scanner sweep back and forth lighting the LEDs without any sort of transition between them. The configuration most familiar to us all as featured in Knight Rider and Battlestar Galactica are a bit more complex, and have a fading trail of light that follows behind the leading edge of the sweep. [Mike] notes that this fading is traditionally accomplished through the use of capacitors, which cause the light to gradually fade as the animation sweeps across the LED array. He decided to take a different route with his circuit, relying on PWM control of the LEDs instead.

Mike put together a simple circuit using an ATmega168, a handful of resistors, and of course, an array of LEDs. Utilizing interrupts and PWM, he was able to accurately recreate the iconic light sweep without the use of any capacitors. One big benefit to his design aside from the lower component count is the fact that he can easily adjust the speed of the sweep as well as the fading properties with a few small code tweaks.

Be sure to check out his blog at some point, where he shares his code, some circuit diagrams, and plenty more details on how his scanner was built. In the meantime, take a look at the video below to see the result of [Mike’s] work.

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Macetech Takes On Its Own Ambilight Clone Hack

October 26, 2011 by Mike Szczys 23 Comments

[Garrett Mace] decided to beef up his 58 inches of plasma with 60 Watts of LED lighting. After seeing a ton of Ambilight clones using his LED modules, he’s built his own powerful system. Not surprisingly, it’s nothing short of professional-grade work.

Kudos to [Garrett] for showing the entire process in the video after the break. We’re talking about his planning stages, which are so often left out of build logs. He first measures the back of the television, and does some testing for distance and angle of the Satellite LED modules to establish how many should be used and to estimate the optimal spacing. From there he modelled a framing system before getting down to the actual build.

The wood frame is made up of a box with a horizontal crossbar serving as a place to mount the drivers. Around the edges, tilting rails were added to make the angle of the LED modules adjustable. As with many other Ambilight clones, [Garrett] uses the boblight software to drive his system and we appreciate it that he included his configuration file for reference. Once up and running the effect is breathtaking (and possibly blinding).

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