Covert Remote Protest Transmitters

As a piece of protest art, “Covert Remote Protest Transmitters” ticks all the boxes. An outdoor covert projector that displayed anti-globalization messages at a G20 summit is protest. To disguise it inside a surveillance camera body housing — sticking it to the man from inside one of his own tools — is art. And a nice hack.

However you feel about the politics of globalization (and frankly, we’re stoked to be able to get cheap tech from anywhere in the world) the open-source DIY guidebook to building the rig (PDF) makes up for it all.

They installed the camera/projector long before the summit, where it sat dormant on a wall. A cell phone inside turned on the projector’s light with each ring because they attached a relay to the cell phone’s speaker circuit. In the instructions there’s an example of using a light-dependent resistor (CdS cell) to do the same thing, relying on the phone’s backlight functionality instead. There are a lot of ways to go here.

The optics consist of a couple of lenses aligned by trial and error, then fixed in place to a balsa wood frame with hot glue. A big fat Cree LED and driver provide the photons.

The video documentation of the piece is great. It’s mostly the news media reacting to the art piece as a “security breach”. A security breach would be a gun or a bomb. This was an overhead projector displaying messages that were out of the organizers’ control. Equating security with the supression of dissent is double-plus-ungood. Touché, CRPT.

Anyway, while you’re getting prepped for your next protest, have a look at the Image Fulgurator.

A Pedal Powered Cinema

When the apocalypse hits and your power goes out, how are you going to keep yourself entertained? If you are lucky enough to be friends with [stopsendingmejunk], you can just hop on his pedal powered cinema and watch whatever movies you have stored on digital media.

This unit is built around an ordinary bicycle. A friction drive is used to generate the electricity via pedal power. In order to accomplish this, a custom steel stand was fabricated together in order to lift the rear wheel off the ground. A 24V 200W motor is used as the generator. [stopsendingmejunk] manufactured a custom spindle for the motor shaft. The spindle is made from a skateboard wheel. The motor is mounted in such a way that it can be lowered to rub the skateboard wheel against the bicycle wheel. This way when the rear bicycle wheel spins, it also rotates the motor. The motor can be lifted out of the way when cruising around if desired.

The power generated from the motor first runs through a regulator. This takes the variable voltage from the generator and smooths it out to a nice even power signal. This regulated power then charges two Goal Zero Sherpa 100 lithium batteries. The batteries allow for a buffer to allow the movie to continue playing while changing riders. The batteries then power the Optomo 750 projector as well as a set of speakers.

CastAR Teardown

A little more than a year ago, castAR, the augmented reality glasses with projectors and retro-reflective surfaces made it to Kickstarter. Since then we’ve seen it at Maker Faire, seen it used for visualizing 3D prints, and sat down with the latest version of the hardware. Now, one of the two people we trust to do a proper teardown finally got his developer version of the castAR.

Before [Mike] digs into the hardware, a quick refresher of how the castAR works: inside the glasses are two 720p projectors that shine an image on a piece of retroreflective fabric. This image reflects directly back to the glasses, where a pair of polarized glasses (like the kind you’ll find from a 3D TV), separate the image into left and right for each eye. Add some head tracking capabilities to the glasses, and you have a castAR.

The glasses come with a small bodypack that powers the glasses, adds two jacks for the accessory sockets, and switches the HDMI signal coming from the computer. The glasses are where the real fun starts with two cameras, two projectors, and a few very big chips. The projector itself is a huge innovation; [Jeri] is on record as saying the lens manufacturers told her the optical setup shouldn’t work.

As far as chips go, there’s an HDMI receiver and an Altera Cyclone FPGA. There’s also a neat little graphic from Asteroids on the board. Video below.

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Digital Light Processing, So Many Tiny Mirrors

Did you know there are a million little mirrors flickering back and forth, reflecting light within some modern projectors; like a flip-dot display but at the micro level? In his video, [Ben Krasnow] explains the tiny magic at work in DLP, or digital light processing technology with a scaled up model he constructed of the moving parts.

LCD projectors work much like old slide projectors. Light is shined through a transparent screen containing the image, which is then focused and enlarged through a lens. DLP projectors however achieve the moving image in a slightly different way. A beam of focused light is shined onto a chip equipped with an array of astonishingly small mirrors. When the mirror is flipped in one direction, it reflects the light out through the lens and creates a visible pixel. When the mirror is tilted the opposite direction, no light is reflected and the pixel is dark. All of these tiny moving parts are actuated by means of static electricity, and since a pixel can effectively only either be in an on or off state without any range of value in-between, the pixel must flutter at a rate fast enough to achieve the illusion of intensity, much like pulsing an LED to create a dimming effect.

In addition to slicing open the protective casing of one of these tiny micro-mirrored chips to give us a look at their physical surface under a microscope, [Ben] also built his own functioning matrix from tiles of mirrors and metal washers sandwiched around pieces of string. A wound electromagnet positioned behind each tile tilts the pixel into position when a current is run through the wire — although he didn’t sink the time needed to build out the full array in this manner (and we don’t blame him). If you do have the time and add in a high powered flash-light, this makes for an awesome way to shine messages on your roommate’s wall.

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Augmented Reality Pinball

Pinball machines are fascinating pieces of mechanical and electrical engineering, and now [Yair Moshe] and his students at the Israel Institute of Technology has taken the classic game one step further.  Using computer vision and a projector, this group of engineers has created an augmented reality pinball game that takes pinball to a whole new level.

Once the laptop, webcam, and projector are set up, a course is drawn on a whiteboard which the computer “sees” to determine the rules of the game. Any course you can imagine can be drawn on the whiteboard too, with an interesting set of rules that no regular pinball game could take advantage of. Most notably, the ball can change size when it hits certain types of objects, which makes for a very interesting and unconventional style of play.

The player uses their hands to control the flippers as well, but not with buttons. The computer watches the position of the player’s hands and flips the flippers when it sees a hand in the right position. [Yair] and his students recently showed this project off at DLD Tel Aviv and even got [Shimon Perez], former President of Israel, to play some pinball at the conference!

Cairo Hackerspace Gets A $14 Projector

The Cairo hackerspace needed a projector for a few presentations during their Internet of Things build night, and of course Friday movie night. They couldn’t afford a real projector, but these are hackers. Of course they’ll be able to come up with something. They did. They found an old slide projector made in West Germany and turned it into something capable of displaying video.

The projector in question was a DIA projector that was at least forty years old. They found it during a trip to the Egyptian second-hand market. Other than the projector, the only other required parts were a 2.5″ TFT display from Adafruit and a Nokia smartphone.

All LCDs are actually transparent, and if you’ve ever had to deal with a display with a broken backlight, you’ll quickly realize that any backlight will work, like the one found in a slide projector. By carefully removing the back cover of the display, the folks at the Cairo hackerspace were able to get a small NTSC display that would easily fit inside their projector.

After that, it was simply a matter of putting the LCD inside the display, getting the focus right, and mounting everything securely. The presentations and movie night were saved, all from a scrap heap challenge.

The R2D2-‘O-Lantern Reddit Doesn’t Want You To See

The people here at Hackaday aren’t dedicating their entire lives to moderating comments and sending press releases to the circular file; some of us actually have jobs and hobbies. [James Hobson] works at a projector company that was having a pumpkin carving contest today. He came up with the best possible use of a pumpkin projector – a R2D2-‘o-lantern that plays the message from [Leia] to [Obi-Wan Kenobi]. [James] submitted this to reddit, but one of the mods deleted it. We’re much cooler than a few mods and their little empire, so we’re putting it up here.

Instead of a knife, [James] used a rather interesting method for carving a pumpkin – a laser cutter. By maxing out the Z height of his laser cutter, he was able to cut a perfect R2D2 graphic on the surface of a pumpkin. No, [James] isn’t removing any of the pumpkin’s skin after the lasering is done, but the result still looks great when backlit.

Inside the pumpkin is a projector playing the famous distress message made from the captured Tantive IV. It’s not entirely accurate – [James] put the projector behind R2’s radar eye and not the holographic projectors, and to project [Leia] in mid-air he would need something like this, Still, it’s a great project we expect to see cloned a year or so from now.