You think you like RGB LEDs? Columbus, OH art professor [Matthew Mohr] has more blinkenlove than you! His airport– convention-center-scale installation piece is an incredible 850,000 RGB LEDs wrapped around a 14-foot tall face-shaped sculpture that projection-maps participants’ faces onto the display. To capture images, there is also a purpose-built room with even illumination and a slew of Raspberry Pi cameras to take pictures of the person’s face from many angles simultaneously.
Besides looking pretty snazzy, the scale of this is just crazy. For instance, if you figure that the usual strip of 60 WS2812s can draw just about 9.6 watts full on, that scales up to 136 kW(!) for the big head. And getting the control signals right? Forgeddaboutit. Prof. [Mohr], if you’re out there, leave us some details in the comments.
(Edit: He did! And his website is back up after being DOSed. And they’re custom LEDs that are even brighter to compete with daylight in the space.)
EE and firmware developer [Enrico] had played with LEDs as a kid, burning out his fair share of them by applying too much current. With the benefit of his firmware chops, he set about creating a board that drives LEDs properly.
[Enrico]’s project centers around a Texas Instruments LM3405 buck controller. It accepts input voltage from anywhere from 3V to 20V and outputs up to 20V/15W to one or more LEDs. He built a ton of safety features into it like short-circuit and open-circuit immunity, temperature control, and auto-off switching when idle. He also created a LED board to test the maximum efficiency of the driver. It consists of four Luxeon Rebel ES diodes, one each RGB and W. The entire back of the LED board is copper, with a monster heat sink attached.
Coca-Cola has updated their sign in Times Square, and this one has a mesmerizing 3D aspect to it, giving the spooky feeling you get from watching buildings curl up into the sky in the movie, Inception. That 3D is created by breaking the sign up into a 68’x42′ matrix of 1760 LED screens that can be independently extended out toward the viewer and retracted again. Of course, we went hunting for implementation details.
On Coca-Cola’s webpage listing the partners involved in putting it together, Radius Displays is listed as responsible for sign design, fabrication, testing and installation support. Combing through their website was the first step. Sadly we found no detailed design documents or behind-the-scenes videos there. We did find one CAD drawing of a Moving Cube Module with a 28×28 matrix of LEDs. Assuming that’s accurate then overall there are 1,379,840 LEDs — try ordering that many off of eBay. EDIT: One behind-the-scenes video of the modules being tested was found and added below.
So the patent hunting came next, and that’s where we hit the jackpot. Read on to see the results and view the videos of the sign in action below.
The basic throwie is a a type of street art/graffiti/vandalism — depending on where you stand — consisting of a coin cell, an led, and a magnet taped together. Seeking to be a slightly more eco-friendly troublemaker, [Alaric Loftus] has kindly put together an Instructable on how to build a solar-powered throwie!
In order to be the best maker of mischief possible, [Alaric Loftus] tried a number of different products to find one that was hackable, supplied the right voltage, had the right form factor, and cheap enough to literally throw away. Turns out, garden path lights hit that sweet spot. Once [Alaric Loftus] has drilled a hole in the light and opened it up, de-soldering the stock LED, attaching some leads to the contacts and sticking it into the freshly-drilled hole is simply done. Hot-gluing a strong magnet on the bottom completes the throwie.
[Alaric Loftus] also advises that drilling the LED hole slightly smaller and sealing up any cracks with hot glue will strengthen its water resistance — because if it’s worth doing, it’s worth doing it right.
We’ve featured some really cool — even creepy — takes on the throwie concept, but please don’t contribute any further to e-waste buildup.
In a previous article, I discussed LEDs in general and their properties. In this write-up, I want to give some examples of driving LEDs and comparing a few of the most commonly used methods. There is no “one size fits all” but I will try and generalize as much as possible. The idea is to be able to effectively control the brightness of the LED and prolong their life while doing it. An efficient driver can make all the difference if you plan to deploy them for the long-haul. Let’s take a look at the problem and then discuss the solutions. Continue reading “Control Thy LED”→
When you need to quantify the color of an object, you’ve got quite a few options. You can throw a Raspberry Pi camera and OpenCV at the problem and approach it through software, or you can buy an off-the-shelf RGB sensor and wire it up to an Arduino. Or you can go back to basics and build this reflective RGB sensor from an LED and a photocell.
The principle behind [TechMartian]’s approach is simplicity itself: shine different colored lights on an object and measure how much light it reflects. If you know the red, green, and blue components of the light that correspond to maximum reflectance, then you know the color of the object. Their sensor uses a four-lead RGB LED, but we suppose a Neopixel could be used as well. The photosensor is a simple cadmium sulfide cell, which measures the intensity of light bouncing back from an object as an Arduino drives the LED through all possible colors with PWM signals. The sensor needs to be white balanced before use but seems to give sensible results in the video below. One imagines that a microcontroller-free design would be possible too, with 555s sweeping the PWN signals and op-amps taking care of detection.
We love seeing a thing get used effectively for other than its intended purpose, and this DIY LED Earrings project is a great example. [IdunnGoddess] liked the idea of making light-up LED earrings powered by a small coin cell, but an enclosure and power connection for the battery were sticking points. The solution? A googly eye after a few minor modifications turned out to be perfect.
A googly eye resembles a thin, flat, hollow plastic bulb. Choose one that’s just a bit bigger than the coin cell, and cut a slot in one end and a small hole in the other. The LED leads go into the hole, and the coin cell slides into the slot. The result? A lightweight battery holder for an attached LED, and as a bonus the hacked googly eye is a clean and super smooth surface that can easily be painted or decorated to make it part of the design. The video embedded below demonstrates the process and showcases a few sample designs.