The Biggest Super Hexagon Fan

For those who haven’t addicted themselves to Super Hexagon yet, it’s pretty… addicting, to say the least. Normally this 80’s arcade-style game would run in a browser but some of the people at Club de Jaqueo in Buenos Aires decided to cram all of that into an Arduino. They didn’t stop there, though, and thought that it would work best with a POV display.

To navigate the intricate maze of blending a POV display with a fast-paced game like this, the group turned to the trusty Arduino Micro. After some frustration in the original idea, they realized that the game is perfectly suited for a POV display since it’s almost circular. The POV shouldn’t take up too much of the processing power of the Arduino, so most of the clock cycles can be used for playing the game. They couldn’t keep the original name anymore due to the lack of hexagon shape (and presumably copyrights and other legal hurdles), but the style of the original is well-preserved.

The group demonstrated their setup this past weekend, and the results are impressive judging by the video below. They’ve also released their source code and schematics as well, in case you have an old fan (or maybe even a bicycle?) lying around that is just begging to be turned into a mini-arcade game.

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Disk Hack Creates Persistence of Vision

[Adam Antok] was compelled to create this repurposed hard drive persistence of vision hack after seeing a toy of the same nature.

hdd-display-schematicHe used the frame, disk and motor from a drive and added LEDs under the spinning disk as the light source. The disk has 8 small holes drilled equidistant around the disk, and spiraling slightly toward the center. As the holes pass by the LEDS they are flashed by the ATtiny2313 processor to create images. To determine the position of the platters a Hall effect sensor is monitored by the 2313 to detect a magnet on the underside of the disk. There is room to display ten characters at one time. Each cursor position can scroll through the character set by rotating an encoder. For all the precision needed to coordinate the LEDs with the spinning holes the electronics and software code are amazingly simple. That’s a really nice job, [Adam]!

Persistence of vision hacks are to hackers like flames are to moths. One really nice thing about [Adam’s] project is that you can interact with it while it’s running. Check it out after the break.

For a novel take on POV, check out this slow swinging pendulum clock.

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Shedding Light on the Mechanics of Film Projection

Do you know how a film projector works? We thought we did, but [Bill Hammack] made us think twice. We have covered the Engineer Guy’s  incredibly informative videos many times in the past, and for good reason. He not only has a knack for clear explanation, the dulcet tones of his delivery are hypnotically soothing. In [Bill]’s latest video, he tears down a 1979 Bell & Howell 16mm projector to probe its inner workings.

Movies operate on the persistence of vision (POV) principle, which basically states that the human brain creates the illusion of motion from still images. If you’ve ever drawn circles and figure eights in the nighttime air with a sparkler or perused a flip book, then you’ve experimented with POV.

A film projector is no different in theory. Still images on a strip of celluloid are passed between a lamp and a lens, which project the images on to a screen. A device called a shuttle advances the film by engaging its teeth into the holes on the edge of the film and moving downward, pulling the film with it. The shuttle then disengages its teeth and moves up and forward, starting the process again.

shuttersFilm is projected at a rate of 24 frames per second, which is sufficient to create the POV illusion. A projector’s shutter inserts itself between the lamp and the lens, blocking the light to prevent projection of the film’s physical movement. But these short periods of darkness, or flicker, present a problem. Originally, shutters were made in the shape of a semi-circle, so they block the light half of the time. Someone figured out that increasing the flicker rate to 60-70 times per second would have the effect of constant brightness. And so the modern shutter has three blades: one blocks projection of the film’s movement, and the other two simply increase flicker.

[Bill] explains how the projector reads the optical soundtrack. He also delves into the mechanisms that allow continuous sound playback alongside intermittent projection of the image frames. You’ll never look at a projector the same way again.

Want to know more about optical soundtracks? Check out this Retrotechtacular that explores the subject in detail.

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Hacklet 32 – LED Persistence of Vision Displays

Blinking LEDs are good. Moving, spinning things are good too. Put them both together and you get a Persistence of Vision (POV) display. Hackers have been building these displays for years. This week’s Hacklet focuses on some of the best LED POV displays on!

povtypeWe start with [EduardoZola] and POV as you type, write on the air. [Eduardo] used an Arduino Nano, a pair of 433 MHz radios, some blue LEDs and a motor to create a simple spinning display. A hall effect sensor keeps everything in sync. The entire display is powered by a 500 mAh LiPo battery. The awesome thing about this display is the interactive aspect. The transmitter module connects to a laptop via an on-board USB to serial converter. Typing into any serial terminal sends the text directly to the POV display, where the letters appear to hang in the air.


deathringNext up is [boolean] with Silent Orchestra POV aka “Death Ring”. [boolean] didn’t want to just create a POV ring, he wanted a huge 5 foot diameter display for his local Burning Man decompression. Death Ring is an aluminum ring spun by a 3HP motor. A hall effect sensor keeps everything synced up, and keeps Death Ring’s 3 horsepower motor in check. Light is provided by a PixelPusher and WS2812 RGB strips. The system is designed to be interactive, controlled with a Leap Motion controller or a Microsoft Kinect. An MPU-6050 keeps acceleration in check while processing maps video to the LED strip. An Arduino Yun allows the entire system to be controlled via WiFi. [boolean] and his team have taken Death Ring through several revisions. Judging by the quality of their aluminum welding though, they’re on the right track to an awesome end result! power user [Davedarko] has been working on a POV display of a different sort. His Locomatrix is an 8×8 LED matrix which moves in and out on the Z axis. [Dave] originally created Locomatrix as his entry in the 2014 Hackaday Prize. We have to admit this is the first time we’ve seen this sort of display, but the idea is sound. In fact, [Bruce Land] posted in the comments to let [Dave] know that he’d seen a similar technique used with a CRT display back in 1964. We’re betting Dave’s 3D printed gears and LED matrix display will be more robust than a CRT tube slamming two and fro at several hundred pulses per minute!

CPOVFinally, we have Hackaday’s own [Mike Szczys] with CPOV – a Crappy Persistence of Vision display . CPOV is a proof of concept made from upcycled parts which [Mike] threw together in a couple of hours. He grabbed the motor from an old cassette deck, some plywood, perfboard, and of course LEDs to build his display. The processor is an ATtiny2313 running Adafruit’s MiniPOV 3 firmware. The system display doesn’t have a sync input, so [Mike] uses a novel form of Human-in-the-loop PWM control to keep the motor speed in check. CPOV is proof that isn’t just for polished projects, but for proof of concepts, fails, and just plain research. Even if your project isn’t perfect, documenting it will help you learn from it. It might even inspire someone else to move forward and continue where you left off!

Want more POV goodness? Check out our new POV display list!

Our LEDs are going dim, so that’s about all the time we have for this Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of!

Arduino Tetris on a Multiplexed LED Matrix

[Alex] needed a project for his microcomputer circuits class. He wanted something that would challenge him on both the electronics side of things, as well as the programming side. He ended up designing an 8 by 16 grid of LED’s that was turned into a game of Tetris.

He arranged all 128 LED’s into the grid on a piece of perfboard. All of the anodes were bent over and connected together into rows of 8 LED’s. The cathodes were bent perpendicularly and forms columns of 16 LED’s. This way, if power is applied to one row and a single column is grounded, one LED will light up at the intersection. This method only works reliably to light up a single LED at a time. With that in mind, [Alex] needed to have a very high “refresh rate” for his display. He only ever lights up one LED at a time, but he scans through the 128 LED’s so fast that persistence of vision prevents you from noticing. To the human eye, it looks like multiple LED’s are lit up simultaneously.

[Alex] planned to use an Arduino to control this display, but it doesn’t have enough outputs on its own to control all of those lights. He ended up using multiple 74138 decoder/multiplexer IC’s to control the LED’s. Since the columns have inverted outputs, he couldn’t just hook them straight up to the LED’s. Instead he had to run the signals through a set of PNP transistors to flip the logic. This setup allowed [Alex] to control all 128 LED’s with just seven bits, but it was too slow for him.

His solution was to control the multiplexers with counter IC’s. The Arduino can just increment the counter up to the appropriate LED. The Arduino then controls the state of the LED using the active high enable line from the column multiplexer chip.

[Alex] wanted more than just a static image to show off on his new display, so he programmed in a version of Tetris. The controller is just a piece of perfboard with four push buttons. He had to work out all of the programming to ensure the game ran smoothly while properly updating the screen and simultaneously reading the controller for new input. All of this ran on the Arduino.

Can’t get enough Tetris hacks? Try these on for size.

Hacking the Crayola Digital Light Designer

[Harry] wrote in with his hack of the Crayola Light Designer. The Light Designer is a pretty unique toy that lets kids write on a cone-shaped POV display with an infrared light pen. [Harry] cracked one open and discovered it has a spinning assembly with a strip of 32 RGB LEDs for the display and a strip of photodiodes to detect pen position. These were ripe for the hacking.

The spinning assembly uses several slip ring connections to send power and data to the spinning assembly. [Harry] connected a logic analyzer to several of the connections to determine which lines were clock, data, and frame select (the strip is split into 2 16-led “frames”). He went on to reverse-engineer the serial protocol so he could drive the strips himself.

Instead of reverse-engineering the microcontroller on the product’s PCB, [Harry] decided to use a Leostick (Arduino Leonardo clone) to control the LEDs and spinner. He mounted the Leostick on the shaft of the spinning assembly, and powered it over the slip ring connections. After adding some capacitance to make up for noisy power from the slip rings, [Harry] had the POV display up and running with his own controller. Check out the video after the break to see the hacked POV display in action.

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Simple POV Bike Effects with WS2811 Strips

[Andrew] wrote in with a new take on the classic persistence of vision bike spoke hack. While many of these POV setups use custom PCBs and discrete LEDs, [Andrew]’s design uses readily available off-the-shelf components: WS2811 LED strips, an Arduino, an Invensense IMU breakout board, and some small LiPo batteries.

[Andrew] also implemented a clever method of controlling his lights. His code detects when the rider taps the brakes in certain patterns, which allows changing between different light patterns. He does note that this method isn’t incredibly reliable due to some issues with his IMU, so now he senses when the rider taps on the handlebars as well.

If you want to build your own bike POV setup, you’re in luck. [Andrew] wrote up detailed instructions that outline the entire build process. He also provides links to sources for each part to make building your own setup even easier. His design is pretty affordable too, coming in at just under $50 per wheel. Check out a video of [Andrew]’s setup in action after the break.

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