If you’re going to use your bicycle as transportation at night you really must have a head and tail light in hopes that the crazy drivers don’t hit you. For good reason, these lights don’t turn themselves off. But [Miceuz] kept forgetting to shut it down upon arrival and always ended up with dead batteries. His quest for an auto-off feature that actually worked ended in a brilliant and simple add-on circuit.
He first thought about using an accelerometer, but couldn’t find one that fit the bill without also adding a microcontroller. He came up with an even simpler circuit, which can be seen at the base of the black plastic housing. It’s a bit of copper clad board with a small spring attached. The spring completes an RC timer circuit which drives a MOSFET. When that circuit is charged, the MOSFET connects power to the bike light. When the cap runs out the MOSFET threshold cuts power and everything turns off. Since the spring jiggles while he rides it provides the momentary connection necessary to charge the capacitor. Stay stationary for about 30 seconds and the auto-off kicks in.
This home automation hardware turns on and off the lights based on room occupancy. The hack is an extension of an earlier version that was only a proof of concept. [RPisces] took the idea and made it into reality by mounting the sensor hardware in a doorway.
He prototyped the device using the MSP430 launchpad. It monitors a pair of IR distance sensors which record a change when something passes between them and the opposite side of the hallway. This is a good sensor choice as it only requires hardware on one side of the passageway. Because two of them are used, it’s quite simple to figure out if a person is entering or leaving the room based on which is tripped first.
In this case [RPisces] drives a relay to switch a lamp on and off. But it could be used for just about anything. We’d enjoy seeing it trigger an audio system like the one [Quinn’s] installing in every room.
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 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.
Continue reading “Femto-photography: Taking pictures of bullets made of light”
[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.
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.
Continue reading “Painting a wall with light using water as ink”
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.
Continue reading “Blinking light switch”