Raspberry Pi Driven 128×32 LED Sign

November 14, 2013 by James Hobson 12 Comments

Looks like a commercial LED display sign… right? Not even close. This is a project of [Jon’s] from over a year ago, and it is a very impressive 128×32 LED display board, driven using a single Raspberry Pi.

It’s made of eight “P10” 32×16 LED panels that he bought off of eBay, housed in a wooden frame he built himself. The display runs off of a single Raspberry Pi and can receive a video signal from anything with an Ethernet port. The individual boards are daisy-chained in a rather odd arrangement to minimize cable length, which [Jon] says helps with clocking the data fast — he’s able to parse 2 bits per pixel to refresh the display at an impressive 400+ frames per second.

To power the display, he’s using a single ATX power supply with the Pi connected to the standby 5V power line. This is to avoid a voltage drop which might cause the Pi to crash — when all LEDs are on the display can draw a healthy 32A of juice. The P10’s use shift registers to serially load the pixel data. At any time, the 4096 pixel display can have 1024 pixels on, which means a fairly fast clock is required to update the display.

[Jon] has shared all the source code on his blog, and has a fairly in-depth explanation of all the systems used. Check it out for yourself, and don’t forget to stick around after the break to see the display in action!

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Peltier Joule Thief Power Supply

November 12, 2013 by Todd Harrison 20 Comments

[Steven] manages to power an LED for 15 minutes using hot and cold water as a battery. He does this using the thermoelectric effect also known as the Seebeck effect, Peltier effect or Thomson effect. This isn’t particularly new; in fact there are commercial products that you can use to charge a cell phone using a small campfire or internal burner that works on the same principle.

What is interesting about [Steven’s] device is that he uses a salvaged Peltier device not meant for generating electricity, coupled with a home built joule thief circuit. In the video he describes how the joule thief functions and powers the LED using the small voltage generated by the Peltier device. The energy for the thermoelectric effect is conducted from a hot water bath through aluminum plates, through the positive and negative sides of the Peltier device, through more aluminum plates and finally into a cold water bath. As the heat energy transfers through the Peltier device a small electric current is generated and flows in two small wires coming out the side of the device. The energy generated by the Peltier device is stored in the joule thief and periodically dumped at a voltage high enough to forward bias the LED “on” for a brief moment. Technically the LED is flashing but at a frequency too high for our eyes to see. As the hot water bath cools, the LED goes from very bright, to dim, to off in about 15 minutes.

Not a very practical power supply but still quite the parlor trick. He wraps up the tutorial specifying that a TEG thermoelectric generator would be a much better choice for generating power and can handle much higher temperatures. You can watch the video after the break.

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Freeside’s Infinity Portal

November 8, 2013 by Marsh 11 Comments

sidebyside

If infinity mirrors aren’t cool enough, the 10-foot-tall infinity portal should blow you away. Strictly speaking, the mirror itself is only 7’x4′, but you’ll still find yourself engulfed in the archway. The portal began as a simple prototype that we covered earlier this summer, which was just a frame of 2×4’s, some acrylic and LED strips. It works by putting lights between a two-way mirror and another mirror, reflecting most light internally and creating the illusion of depth.

The giant archway also began as a small-scale prototype, its shape and engravings carved out by a laser cutter. Once they were satisfied with its design, it was time to scale things up. The full-sized portal needed a a tremendous amount of stability, so the guys at Freeside built the base from wooden palettes. They needed the portal to travel to a few different venues, so the rest of the frame breaks down into components, including a removable wooden frame from which the acrylic hangs. A Teensy 3.0 runs all the WS2812 LED strips, which were chosen because each of their LEDs is individually addressable.

Check out the video below for an extremely detailed build log, which should give you a better idea of how massive and impressive this portal really is!

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Make Your Own LED Lightbulb!

November 3, 2013 by James Hobson 43 Comments

LED lightbulb

Do you like saving electricity? Who doesn’t!

Do you have a lot of LED light strips lying around, destined for a project that you never quite got around to? We’re guilty!

Do you have an old DC power adapter? Of course you do.

Do you love soldering? Duh.

Do you have a dead fluorescent light bulb sitting around? Maybe…

If so, here’s a quick and silly guide to making your very own LED light bulb! The result is a bit ghetto we admit, but quite functional. Perhaps it could be improved by adding a glass Christmas bobble to make it look a bit more like a regular light bulb. And if you’re ambitious enough you could throw a microprocessor in there and add wireless control to it as well … but let’s be honest, smart LED light bulbs are getting quite affordable these days. But hey, you’ve got to do something for entertainment!

LED Bulb Reviews, Evaluations And Teardowns

November 1, 2013 by Todd Harrison 25 Comments

[ElectronUpdate] has posted many great reviews of commercial LED bulbs that one can purchase to replace standard E26 incandescent light bulbs. In his reviews he evaluates the light emitting performance and does a thorough and detailed teardown, evaluating and understanding the circuit technologies used. For the light emission evaluation he uses a light meter and some homemade graph paper to plot the lumens at different angles. Flicker is easily evaluated using a solar panel from a discarded solar path light connected to his oscilloscope. Any flicker will show up quite nicely and can be measured. Of course a kill-a-watt meter makes an appearance in most reviews to read watts and power factor.

Recently [ElectronUpdate] wanted to understand the meaning of CRI which is advertised on many of these commercial LED packages. CRI stands for color rendering index and deals with how colors appear when compared to a natural light source. After doing some researching he found that a CRI over 80 is probably good for LED lighting. The next dilemma was how to measure CRI without expensive scientific equipment. He found a website that we have featured before with free software and instructions on how to build a spectrometer. The web instructions include building a meter box from paper but he found it was much more reliable if built out of wood. We’ll let you follow [ElectronUpdate’s] recommended build if you like, but you’ll need a few items which he does detail.

After a short calibration procedure the final rig will measure power spectral line densities of your light source. [ElectronUpdate] is promising more details on how the colorful measurement data can be related to CRI ratings, but you can get a jump on the details at Full Spectrum Solutions. We also recommend you browse through all of [ElectronUpdate’s] LED bulb reviews on YouTube if the progressing performance and innards of LED bulbs fascinates you as much as it does us.

Hackaday Logo Projector From A Single LED

October 31, 2013 by Mike Szczys 11 Comments

Here’s another Trinket Contest entry that was interesting enough for its own feature. [Adam] made his own Hackaday version of the Bat signal. It’s not nearly as big, but the concept is the same. Using this single modified LED he’s able to project a 12″ image that seems quite well-defined (more pictures below).

The LED is one he pulled from an old flashlight. After sanding the dome flat he made a jig which positioned it inside of his laser cutter. From there he etched the 0.1″ logo and filled the negative space with some ink. The remaining surface was polished to help the light shine through, then positioned in front of a jeweler’s loupe to magnify the image.

There’s just a couple of hours left before the Trinket Contest draws to a close. Get your entry in for a chance to win!

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Light Controller Goes Overboard For Halloween

October 31, 2013 by Mike Szczys 15 Comments

floodbrain-halloween-light-controller

Yep, we said it. This Halloween decoration goes way overboard… and we love it! Not only does [Shelby Merrick] put on an incredible sound and light show for the neighborhood, but he keeps us happy by posting all the details for the lighting controller he designed. He calls the creation FloodBrain as it’s switching a set of flood lights to achieve the effects seen above. But for the full experience you’ll want to watch the demo videos below as well.

He needed a way to switch twelve RGB flood lights which pull 10 Watts. His controller was designed to communicate with them via RS485, with an AVR Xmega8E5 controlling the system. We like it that he included some images of the manufacturing process, using a stencil for solder paste before placing components for reflow.

The floodlights themselves are also an interesting hack. To get what he wanted at the best price he picked up 10W white LED flood lights for about eight bucks a piece, then swapped out the LED itself for an RGB version (same wattage) using the same heat sink and case.

More often that not we see this type of system controlling Christmas lights. [Shelby] mentions that he did get help from Christmas light controller forum We also think he should have no problem repurposing the controller for that type of application.

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