Hackaday Links: December 15, 2013

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Want to get a hold of a gaming controller attachment for iOS at a rock bottom price? [Dark GOD] learned that Amazon is closing out the Gameloft DUO Gamer hardware for $6 because the hardware is no longer supported by the operating system. He shows how to make it work using a Cydia app. [Thanks ProMan]

[Frank Zhao] had a cheap HDMI switch which had problems with a sagging power rail. His solution was to hack in a USB port to inject some power.

This security hack uses an Arduino with LCD screen to display a QR code. Scan it with an Android device and you no longer need keys! Here’s the code repo and a demo video.

It’s interesting to see how many places the WS28xx pixels are popping up. Here’s a crowdfunding campaign that uses a matrix of the pixels as a portable gaming display. Look somewhat familiar? We’ve seen [Retro Brad’s] earlier hardware (made to play Super Pixel Bros.) that used an LED module instead. This is probably a lot easier to drive since it uses serial data instead of multiplexing.

Next is some robot building inspiration. [IronJungle] has been hard at work building a rover that uses compass bearings for navigation.

We liked seeing a drop-in replacment uC for Ikea Dioder projects, but if you need more power under the hood, take command of those colored lights with a Raspberry Pi.

Those lucky enough to have access to a laser cutter will find this Inkscape extension for living hinges useful.

Finally, POTUS threw down the gauntlet, encouraging everyone to learn how to program by pointing them toward the Hour of Code program. We’ve long thought that everyone should have some level of coding education. Do you agree with us? Of course, getting something like this into schools is a monumental challenge, so it’s nice to see extra-curricular offerings. We also believe that Hackerspaces are among the best driving forces for getting kids a tech education. [via Adafruit]

Build An In Line Network Bandwidth Monitor

[Kurt] likes to know what’s going on with his network. He already uses bandwidth checking software on his DD-WRT capable router, but he wanted a second opinion. So he built his own network monitor. [Kurt] started by building a passive Ethernet tap. He then needed a network interface chip that would serve his purposes. The common Wiznet chips used with Arduinos didn’t allow enough manipulation of raw packet data, so he switched to a Microchip ENC624J600 (PDF). The Microchip controller allowed him to count the bytes in the raw Ethernet packets.

With the Ethernet interface complete, [Kurt] turned his attention to a microcontroller to run the show. He started with an Arduino, but the lack of debugging quickly sent him to an Atmega128 in Atmel Studio. After getting the basic circuit working, [Kurt] switched over to a PIC24F chip. With data finally coming out of the circuit, he was able to tell that his original back-of-the-napkin calculations for bandwidth were wrong. [Kurt] created a PCB to hold the microcontroller, then wrote a Python program to plot the data output from his circuit. The bandwidth plot matched up well with the plot from DD-WRT. Now he just needs a giant LED matrix to show off his current network stats!

Cast A Shadow, Play A Note

Looking for a way to entertain friends and family this holiday season? Look no further than the Arduino-powered Photocell Piano. [Asahillis] has posted this Instructable for building a 6-note musical command center.

The piano uses photoresistors to turn each note on when the player runs their hand over it. Notes can be tuned independently using potentiometers on the front of the box. The hack uses two circuits: one to generate the tones, and a second to mix them. [Asahillis] adapted [Forest Mims III]’s timeless schematics for the 555 Tone Maker and the 741 Audio Mixer to create his Photocell Piano.

When the instrument is powered on, the code takes a 5-second reading of the ambient light, and sets a threshold based on its findings. Afterward, the first note will sound, indicating the piano is ready to be played. Each note has its own if-else statement that tells it to sound when its corresponding  photoresistor reaches a value below the set threshold (when the player casts a shadow). There’s a demo video included in the guide but we couldn’t embed it here.  Check out the demo video after the break.

If you prefer to rock out with your lights out, there’s always this impressive laser harp.

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Fubarino Contest: A Shifter With An Easter Egg

shifter

A few months years ago [Wes] shared a project of his on the Hackaday Forums (yes, we do have a forum and you should check it out). He created a shifter for some sim racing, greatly improving on any system that uses a keyboard.

The shifter is made out of some scrap wood, a cutting board cut with an H-gate shape, and a few arcade microswitches. A giant bolt locks into a few cabinet clasps for each gear position, and the set of microswitches connected to a USB game pad tell [Wes’s] virtual car what gear he should be in.

It’s a great build, but because this is an entry for our Fubarino contest, [Wes] needed to put an easter egg with the Hackaday URL in there somewhere. To solve this problem, [Wes] upgraded the electronics with a Teensy 2.0. When the gears are shifted into 1st, 3rd, 3rd, and 7th, the Teensy blinks the URL in Morse and opens up a web browser that loads up Hackaday.

Not only is it a great build, it’s also a very, very subtle easter egg for our favorite website. Demo of the egg below.

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Raspberry Pi Wall Calendar

Do you let Google know every aspect of your personal and social life? Do you have a spare LCD monitor kicking around? Why not make your own Raspberry Pi Wall Calendar?

[Alex] recently bought his first home (congratulations!), which happened to have a TV wall mount in the kitchen. Personally, we don’t think TVs belong in the kitchen, and neither did [Alex]. Not wanting to tear the mount out of the wall (and thus require home renovations too soon), he devised a clever solution: why not make a digital calendar?

[Alex] connected a Raspberry Pi model B to the LCD monitor, which provides convenient access to his Google Calendar. His Instructable is both meticulous and approachable, so novice hackers should have no trouble replicating this build. The only improvement we can think to suggest is substituting a touchscreen LCD, which would allow him to interact with the schedule.

Whether you “let” Google know about your life— or it just knows—this is certainly a handy hack for the 21st century home!

Controlling High Voltage 7-Segment Displays

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The MAX7219 is one of those parts in your bin that has a “done and done” attitude. In case you’re unfamiliar, this chip can be used to control 7-Segment displays, 8×8 Matrix displays, or even a pile of random LEDs. You talk to it via a simple serial interface and it handles the tasks you don’t want to fuss with, such as multiplexing and modulation. Not all displays are alike, however, so [Raj] wrote in to show how he used the MAX7219 to control high voltage 7-segment displays.

The spec on the MAX7219 only allows an input voltage of 5V, which limits the driver output to around 4V and can cause problems when using large displays that series-connect LEDs internally. [Raj’s] solution allows the MAX7219 to control displays with combined forward voltages of up to 24V, and as an added bonus, the circuit maintains compatibility with existing microcontroller libraries. We imagine this could be a nifty trick to keep on hand the next time you need to control large scoreboard displays.

The circuit works with the help of intermediate drivers to essentially level-shift the voltage to the display, which both provides the high voltage and protects the MAX7219’s inputs. One of the drawbacks of this circuit is losing the MAX7219’s constant current feature, requiring that each segment connection includes a current-limiting resistor. We appreciate this design’s attention to default states, because you wouldn’t want all of your LEDs turning ON during boot-up!

Digital Electric Meter Monitor Goes Old School

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[Sal] sent us his digital electric meter monitor, which immediately made us nostalgic for some of Forrest Mims’ books. Sal’s schematic and circuit description are similar to Forrest’s style, and we mean that as a compliment. Even in today’s world of CAD and EDS packages, sketching out a circuit by hand is sometimes both easier and faster. The schematic isn’t the only classic aspect of [Sal’s] design. He’s collecting data using a parallel port on an unused PC: in this case, a Toshiba Libretto running Windows 95. Before cheap flash-based microcontrollers and dev boards were available, the PC parallel port was the go-to hardware hacking interface for many of us. Plenty of the software running those old hacks was written in basic, and [Sal’s] meter is no exception. His software runs on Microsoft QBasic, which shipped with Windows 95.

The circuit takes advantage of the digital meter’s output: a 10 ms pulse for every 1 Wh of energy used. An IR photo detector from RadioShack detects the meter pulses, which are amplified by an LM324 Op Amp. An NPN transistor then shifts the output to send it to two 74LS73 JK flip flops. The first flip flop uses a transistor to drive an LED for visual output. The second JK flip flop sends the data to the PC. The flip flop has the effect of dividing the number of meter pulses by two, creating a much longer toggled signal that a PC can better detect.

Although using an AVR or PIC would consume less power, [Sal’s] setup has already more than paid for its power usage. By monitoring and adapting his electrical usage, [Sal] is saving $20 a month on his electric bill. We’ve included [Sal’s] circuit diagram and source code after the break (apologies to our readers on RSS).

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