Must-Have Overkill Christmas Tree Lights

The yuletide fire is out, so we’re starting to receive this year’s Christmas hacks. [Chris] sent us his awesome video-mapped tree lighting hack. His project made clever use of a bunch of cool tools, so even if you’re not thinking forward to next December, it’s worth a look. Still images don’t do it justice; check out the video below the break.

The end result is an addressable string of WS2812B LEDs connected up to a Raspberry Pi Zero that can display a video image even though it’s wrapped around a roughly cone-shaped (pine) object. But this is actually more impressive than you’d think at first; how would you map a flat image to a string of LEDs wrapped around a tree?

[Chris]’s solution was to write a routine that lit up the LEDs in a unique pattern and then detected them using OpenCV and a webcam, making the mapping directly. He then samples images from a video at exactly the points where the pixels are located on the tree, and sends this data out to the LEDs.

The basic framework here should transform fairly easily into a generic image-mapping procedure with randomly located LEDs, so we think it’s a hack that’ll outlast the season. And because it runs on the Pi Zero, everything is in Python so it’d be a good project for beginners to replicate. However, the code section on the project page still lists it as coming soon. We hope so!

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POV Globe Display Spins up Full Color Tupac

Persistence of vision projects were once all the rage, judging by a quick review of the literature here on Hackaday. They’ve tapered off a bit lately, but this impressive full-color globe display might just kick-start some new POV projects.

Built as a final project for an EE course, [Evan] and [Kyle]’s project is more about the control electronics and programming than the mechanical end of the build. Still, spinning a 12″ ring of 1/4″ thick acrylic with a strip of APA102 LEDs glued to the edge takes some thoughtful engineering. While the build appears sturdy, [Evan] does admit to a bit of wobble under full steam, which was addressed by adding some weight to the rig. We wonder if mounting half the LEDs on each side of the ring to balance the forces wouldn’t have worked better. True, it would have complicated the coding for the display, but maybe that would have been good for extra points. In any case, the display turned out well and the quality of the images is great. And as an aside: how awesome is it that we live at a time when you can order a six-circuit slip-ring for a project like this for less than $20?

It’s the end of the semester and we love seeing the final projects that have just made it across the finish line. This globe is one, yesterday we saw a voice-controlled digital eye exam, and if you have or know of a final project, don’t forget send us the link!

If POV globes are your thing, be sure to set the Hackaday WABAC machine a few years and check out this Death Star design from 2012 or this globe from 2010.

RGB LED Ceiling Display

yP8PoVDisco Floor’s are passé. [dennis1a4] turned them upside down and built an awesome RGB LED ceiling display using some simple hardware and a lot of elbow grease. His main room ceiling was exactly 32 ft x 20 ft and using 2 sq. ft tiles, he figured he could make a nice grid using 160 WS2812B RGB LEDs. A Teensy mounted in the ceiling does all the heavy lifting, with two serial Bluetooth modules connected to it. These get connected to two Bluetooth enabled NES game controllers. Each of the NES controller is stuffed with an Arduino Pro Mini, a Bluetooth module, Li-Ion battery and a USB charge controller.

Bluetooth is in non-secure mode, allowing him to connect to the Teensy, and control the LEDs, from other devices besides the NES controllers. The Teensy is mounted at the centre of the ceiling to ensure a good Bluetooth link. Programming required a lot of thought and time but he did manage to include animations as well as popular games such as Snake and Tetris.

LED_Ceiling_deadbugThe hard part was wiring up all of the 160 LED pixels. Instead of mounting the 5050 SMD LED’s on PCBs, [dennis1a4] wired them all up “dead bug” style. Each pixel has one LED, a 100nF decoupling capacitor, and 91 ohm resistors in series with the Data In and Data Out pins – these apparently help prevent ‘ringing’ on the data bus. Check the video for his radical soldering method. Each SMD LED was clamped in a machine shop vice, and the other three parts with their leads preformed were soldered directly to the LED pins.

The other tedious task was planning and laying out the wiring harness. Sets of 10 LEDs were first wired up on the shop bench. He then tacked them up to the ceiling and soldered them to the 14 gauge main harness. The final part was to put up the suspended ceiling and close the 2 sq. ft. grids with opaque plastic.

[dennis1a4]  did some trials to figure out the right distance between each LED and the panel to make sure they were illuminated fully without a lot of light bleeding in to adjacent panels. This allowed him to get away without using baffles between the tiles.

Check out the video to see a cool time-lapse of the whole build.

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Christmas Star uses Two AA Batteries

When [hkdcsf] was a teenager, he made a Christmas star with an up counter driving decoder logic and using transistors to light LEDs in festive patterns. He’s revisited this project using modern techniques including a microcontroller, a DC/DC converter, and constant current LED drivers.

The project uses two AA batteries, and that’s what makes the DC/DC converter necessary. Blue LEDs have a forward voltage of just over 3V, and the LED driver chip requires about 0.6V of overhead. Two fresh AAs will run a tad above 3V, but as they discharge, or if he’s using rechargeables, there just won’t be enough potential. To make sure the star works even with whatever LEDs are chosen, the converter takes the nominal 3V from the batteries and converts it to 3.71V.

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Vintage Video Projector Lives Again

Projectors are getting a lot less expensive these days, what with China pumping out Pico projectors by the boat load and all. But did you know it’s not that hard to convert an old slide projector to digital? [Alec Smecher] shows us how with a 1950’s LaBelle 75 slide projector, and the result is pretty awesome.

dmd_chipDigital projectors can use a few different technologies to work. The best, and brightest is DLP (Digital Light Processing) by Texas Instruments — which is pretty well the world-wide standard for high-end, high-lumen digital projection. It works by bouncing red, green, and blue light off of three DMD’s (Digital Micromirror Devices) which have an array of tiny 2-position mirrors, with each representing a pixel.

One of the older technologies is LCD, which is even easier to understand. You shine white light through a color LCD, and there is your projection. All you need for a projector, then, is an LCD, a light source, and a bit of optics.

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Impressive NFC Controlled Infinity Mirror Table Cuts No Corners

If you’re looking to add a bit of the future to your living room, you might want to look at this tutorial to build a very professional infinity mirror table.

It’s an IKEA RAMVIK coffee table, modified to include RGB LEDs and a one-way mirror for that ever-so-awesome infinity effect. And technically, you only have to cut one hole in the table.

By placing a large mirror underneath the glass, wrapping the inner edge with a strip of RGB LEDs and coating the original glass top with a reflective car tint, it’s a pretty simple hack that results in a very polished product — not something that can be said for most of our projects!  But to make it even better, [Pierre] added an NFC chip under the table, allowing you to control the color with just a tap.

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Hairband Lights Up Depending on your Mood

After learning how to use the ESP8266, [Chirag Nagpal] decided to do a fun project to experiment that polls data from Twitter. He calls it the Sentiband, and it analyses your last tweet’s sentiment and changes color accordingly.

There is an API available called Sentiment140 (Formerly ‘Twitter Sentiment’) which is capable of determining the emotional content of a tweet on Twitter. It uses classifiers built from machine learning, and was developed at Stanford by a few CS graduates. We’ve seen it used before on a Christmas tree ornament on a much larger scale, analyzing all holiday tweets to light up your tree.

[Chirag’s] version allows you to set a username and display the latest sentiment of that user’s tweets hidden in the subtext. Three LEDs light up; green for a positive tweet, red for negativity, and blue for neutral.

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