Cloning a water-based light wall project

A few weeks ago, we featured this water-based LED graffiti art installation that allows anyone to paint in light using only a bottle of water. When one of [Chris]‘ friends saw the video of this build, he immediately asked him how it worked. One thing led to another, and now [Chris] and a few other members at the BUILDS hackerspace at Boston University are building their own water LED installation.

The basic premise of this build is allowing water to serve as a conductor between the anode and cathode of a LED. Without spraying or painting water on the circuit [Chris] whipped up, there is an infinite resistance between the two pins of the LED and current cannot flow. After applying water to the anode and cathode pads, a small amount of current is conducted through the water and the LED lights up.

Right now, [Chris] is working on a test board with different sizes of pads and spacing to get the best water graffiti LED effect for his future build. The plan is to build a single one-meter panel out of one hundred 10 cm x 10 cm boards connected together with jumpers.

All of [Chris]‘ work is up on GitHub, and even though [Chris] hasn’t begun designing the production boards, it’s more than enough to get you started if you’d like your own water LED painting panel.

Femto-photography: Taking pictures of bullets made of light

Femto-photography is a term that derives its name from the metric scale’s prefix for one-quadrillionth. When combined with photography this division of time is small enough to see groups of light photons moving. The effect is jaw-dropping. The image seen above shows a ‘light bullet’ travelling through a water-filled soda bottle. It’s part of [Ramesh Raskar's] TED talk on imaging at 1 trillion frames per second.

The video is something of a lie. We’re not seeing one singular event, but rather a myriad of photographs of discrete events that have been stitched together into a video. But that doesn’t diminish the spectacular ability of the camera to achieve such a minuscule exposure time. In fact, that ability combined with fancy code can do another really amazing thing. It can take a photograph around a corner. A laser pulses light bullets just like the image above, but the beam is bounced off of a surface and the camera captures what light ‘echos’ back. A computer can assemble this and build a representation of what is beyond the camera’s line of sight.

You’ll find the entire talk embedded after the break.

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Cat palace with an automatic heat lamp

[Herpity] was getting tired of his cat manipulating him into turning on a lamp above her bed every time she wanted a nap. She likes the warmth put off by the light bulb but he knew he could do better than that so he built a bed which includes an automatic heat lamp. To help introduce her to the new enclosure he set it on the chair where she normally naps.

The bed has two parts, the lower chamber acts as the sleeping area. There is a false bottom underneath the blanket which acts a platform for the weight sensors which detect when the cat is ready for a nap. A PIC microcontroller monitors two sensors and switches on mains voltage to a heat lamp once the pre-calibrated weight threshold has been reached. The upper part of the enclosure holds all of the electronic components and makes room for the recessed light housing. [Herpity] included an exhaust fan for the upper chamber but it turns out a grating is all he needs to keep the temperature at an acceptable level.

[via Reddit]

Painting a wall with light using water as ink

This art installation uses a fantastic concept. The wall can be painted using water as ink which lights up a huge grid of white LEDs. This offers a very wide range of interactive possibilities since water can be applied in so many ways. Grab a paint brush, wet your finger, use a squirt gun, or mist with a spray bottle and the lights will tell you where you hit the wall.

We’re hoping a reader who speaks both French and English might help out by posting a translation as a comment on the prototyping video. In it, [Antonin Fourneau] shows off the various prototypes that led to the final product and we’d love to know what he’s saying. But by seeing the prototypes, then watching the English promo video after the break we can make a pretty good guess.  The boards have a hole that fits the flat-lens LEDs perfectly. This creates a mostly water tight seal to keep the liquid on one side while the leads are safe on the other. The water side has squiggly pads which allow droplets of water to complete an electrical connection.

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Blinking light switch

In addition to being a great replacement for that aging eye patch, these specs act as a light switch. By watching your eyelids, they are able to kill the lights whenever you blink.

The installation is a shared experience piece conceived by [Michal Kohút]. He wanted to illustrate the constant blinking we all do but rarely think about. The system uses an Arduino to capture events from the blink sensors and switch the lights accordingly. This way the wearer doesn’t experience a loss of illumination, but the observer does. Check out the video after the break for a quick demonstration.

One of the commenters from the source article shared a video link to another blink-based light project. That one uses electrodes attached to skin around your eye in order to detect eyelid motion.

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Revolight clone

[Fabian.E] wanted to light up the rims on his bike, but didn’t want to shell out a bunch of clams to get it done. He came up with this system which uses magnets and reed switches to light up one arc or each bicycle wheel.

He calls it the lightrider and it’s based on the revolights concept. That design uses a microcontroller which is capable of animating patterns when the wheels aren’t spinning. [Fabian's] version can’t do that, but the effect while moving is basically the same. The ring of LEDs around the rim is connected to a battery via a set of reed switches. When these switches move past a magnet on the fork it completes the circuit and switches on that segment of LEDs. The clip after the break gives a demonstration of the finished product, and includes a fast-motion video of the fabrication process.

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LED bicycle hack makes sure you’re seen at night

The bicycle tail and head lights that we’re accustomed to are small add-on modules. This take on the idea uses strips of LEDs to protect you from behind. They’re very bright, matching the pair of LED headlights that are attache to the handlebars.

Apparently [A.Davis12] had some LED strips laying around. There’s not what we’re used to seeing, but they have a similar footprint so you should be able to substitute the kind that come on a spool and may be cut to length. The majority of the build time was spent integrating the lights and their control wires with the frame of the bike. The frame already has holes in it for feeding the control wires for brakes and gear shifting inside the tubing. It sounds like it was a pain, but eventually he managed to get all of the routing done. Two red strips are zip-tied to the back of the seat stays. They are powered by a lithium battery inside the project box which mounts under the back of the saddle. A flip switch on the case lets you turn them on without stopping.

[Thanks Arpad]