Hackaday Prize Entry: Cheap Visible Light Communication

[Jovan] is very excited about the possibilities presented by Visible Light Communication, or VLC. It’s exciting and new. His opening paragraphs is filled with so many networking acronyms that VLC could be used for, our browser search history now looks like we’re trying to learn english without any vowels.

In lots of ways he has good reason to be excited. We all know that IR can communicate quite a bit, but when you’re clever about frequency and color and throw in some polarizers with a mix of clever algorithms for good measure you can get some very high bandwidth communication with anything in line of site. You can do it for low power, and best of all, there are no pesky regulations to stand in your way.

He wants to build a system that could be used for a PAN (Personal Area Network). To do this he’ll have to figure out a way to build the system inexpensively and using less than a watt of power. The project page is full of interesting experiments and quite a few thesis on the subject of LEDs.

For example, he’s done work on how LEDs respond to polarization. He’s tested how fast an LED can actually turn on and off while still being able to detect the change. He’s also done a lot of work characterizing the kind of light that an LED emits. We don’t know if he’ll succeed yet, but we like the interesting work he’s doing to get there.

NES Light Gun Fires Awesome Laser Effect

[Seb Lee-Delisle]’s NES lightgun gave us pause as the effect is so cool we couldn’t quite figure out how he was doing it at first. When he pulls the trigger there erupts the beam of light Sci Fi has trained us to expect, then it explodes in a precision sunburst of laserlight at the other end as smoke gently trails from the end of the barrel. This is a masterpiece of hardware and trickery.

Demo video posted by @seb_ly

The gun itself is a gutted Nintendo accessory. It looks like gun’s added bits consist of two LED strips, a laser module (cleverly centered with two round heatsinks), a vape module from an e-cigarette, a tiny blower, and a Teensy.  When he pulls the trigger a cascade happens: green light runs down the side using the LEDs and the vape module forms a cloud of smoke in a burst pushed by the motor. Finally the laser fires as the LEDs finish their travel, creating the illusion.

More impressively, a camera, computer, and 4W Laser are waiting and watching. When they see the gun fire they estimate its position and angle. Then they draw a laser sunburst on the wall where the laser hits. Very cool! [Seb] is well known for doing incredible things with high-powered lasers. He gave a fantastic talk on his work during the Hackaday Belgrade conference in April. Check that out after the break.

So what does he have planned for this laser zapper? Laser Duck Hunt anyone? He has a show in a month called Hacked On Classics where this build will be featured as part of the Brighton Digital Festival.

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20kW Light Is As Bright As You’d Expect

[Photonicinduction] purchased a very very bright light. This 20,000 Watt half meter tall halogen will just about light the back of a person’s skull with their eyes closed. These are typically used to light film sets.

Most people couldn’t even turn such a light on, but [Photonicinduction] is a mad scientist. Making lightning in his attic, it’s easy to mentally picture him as the villain in a Sherlock Holmes novel. Luckily for us, if he has any evil tendencies, they are channeled into YouTube videos.

He gives a good description of the mechanical and electrical properties of the light. The body is as one would expect for an incandescent light. A glass filament envelope with the filaments supported within. The envelope is evacuated and filled with an appropriate gas. This light is dangerous enough that the outside must be thoroughly cleaned of fingerprints to keep a hot-spot from forming, which could cause the lamp to explode.

After some work, he managed to convince himself that the filaments within were not, in fact, garage door springs, and gave a demonstration of their properties. For example, their resistance goes up as they are heated. In order to keep from tripping the power supply, filaments this large must be preheated. Failure to do so passes a very large number of amps.

The next step was to hook the lamp up to his home-made 20 kW power supply. He gives a good demonstration of just how bright it is. Within seconds he’s sweating from the heat and definitely can’t even open his eyes to see with the tiny sun occupying the center of his abode. Video after the break.

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DIY Smart Home Device Means No More Fumbling in the Dark

Smart home tech is on the rise, but cost or lack of specific functionality may give pause to prospective buyers. [Whiskey Tango Hotel] opted to design their own system using a Raspberry Pi and Bluetooth device connectivity. Combining two ubiquitous technologies provides a reliable proximity activation of handy functions upon one’s arrival home.

Electrical Wiring Diagram

The primary function is to turn on a strip of LEDs when [Whiskey Tango Hotel] gets home to avoid fumbling for the lights in the dark, and to turn them off after a set time. The Raspberry Pi and Bluetooth dongle detect when a specified discoverable Bluetooth device comes within range — in this case, an iPad — after some time away. This toggles the Pi’s GP10 outputs and connected switching relay while also logging the actions to the terminal and Google Drive via IFTTT.

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Incredible Luminosity in a Portable Package

If you’ve ever wanted to bring the brightest day into the blackest night, this flashlight shall give you sight. With a 100W LED array powered by up to 32V, this thing is exceedingly bright — it clocks in at about 9000 lumens! But the best part is that all every little detail of the build was documented along the way so that we can tag along for the ride.

The all-aluminium case houses the LEDs and their heat sink, voltage regulator and display, the AD and DC adapter and converter boards and their connectors, and fans to ensure adequate ventilation. It’s powered by a custom-assembled 6400 mAh 11.1V lipo battery or DC 20V 10Amp power supply via XLR for rugged, locking connection. The battery pack connection was vacuum formed for quick-swapping, and the pack itself will sound off an alert if any of the three batteries inside the pack run out of power. A nifty added feature is the ability to check the remaining charge — especially useful if you’re looking to bring this uncommonly powerful flashlight along on camping trips or other excursions.

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Graphene Optical Boom Emits Light with No Diode

When a supersonic aircraft goes faster than the speed of sound, it produces a shockwave or sonic boom. MIT researchers have found a similar optical effect in graphene that causes an optical boom and could provide a new way to convert electricity into light.

The light emission occurs due to two odd properties of graphene: first, light gets trapped on the surface of graphene, effectively slowing it down. In addition, electrons pass through at very high speeds. Interestingly, the speeds are nearly the same–that is, electrons and trapped light travel at almost the same speed. The researchers found a way to make the electrons move faster than the speed of light (in the graphene) and thus created Cerenkov emissions. Because of the structure of graphene, the resulting light is intense and tightly focused.

The researchers speculate that this technique could be important in building graphene-based optical chips. We’ve talked about mixed graphene and semiconductor chips before. Graphene is pretty exotic stuff. It can even fold itself.

Don’t Take Photos of Your Arduino 101 Either, It’s Light Sensitive

Wafer level chips are cheap and very tiny, but as [Kevin Darrah] shows, vulnerable to bright light without the protective plastic casings standard on other chip packages.

We covered a similar phenomenon when the Raspberry Pi 2 came out. A user was taking photos of his Pi to document a project. Whenever his camera flash went off, it would reset the board.

[Kevin] got a new Arduino 101 board into his lab. The board has a processor from Intel, an accelerometer, and Bluetooth Low Energy out of the box while staying within the same relative price bracket as the Atmel versions. He was admiring the board, when he noticed that one of the components glittered under the light. Curious, he pulled open the schematic for the board, and found that it was the chip that switched power between the barrel jack and the USB. Not only that, it was a wafer level package.

So, he got out his camera and a laser. Sure enough, both would cause the power to drop off for as long as the package was exposed to the strong light. The Raspberry Pi foundation later wrote about this phenomenon in more detail. They say it won’t affect normal use, but if you’re going to expose your device to high energy light, simply put it inside a case or cover the chip with tape, Sugru, or a non-conductive paint to shield it.

EDIT: [Kevin] also tested it under the sun and found conditions in which it would reset. Videos after the break.

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