Simple Christmas Tree Christmas Tree Ornament

When the only tool you have is a hammer, every problem looks like a nail. An LED ornament for the Christmas tree can be built in any manner of simple, easy implementations. You certainly don’t need an ARM Cortex M4 CPU running at 120MHz having a mouthful of three letter features like FPU, ETM, ETB, ECC, RWW, TCM, EIC, AES, CAN bus and much, much more. But [Martin Held] built a super simple LED Christmas tree ornament using the ATSAME51 series micro-controller, which he regularly works with and had on hand, and lots of bi-color LEDs. He already had schematic symbols and programmers for the device from other projects where he uses it more extensively, so putting it all together in time for the festive season was that much faster for him, despite the fact that the micro-controller was most likely the cheapest part of the BOM, besides the passives.

At this point it might be tempting to argue that it would have been so much simpler to use addressable LED’s, such as the WS2812B or the APA102C. You can drive them using a more basic micro-controller, and not require so many GPIO pins. But using such “smart pixel” LED’s for hand assembled prototypes can sometimes lead to unexpected results. If they are not stored in sealed tape/reel form, then storage conditions can have an adverse effect leading to dead pixels. And, they need a specific baking procedure before being soldered. Doing that for a few LEDs at home can be tricky.

So for the LED’s, he again went a bit off the beaten path, selecting to use three different color styles of bi-color LED’s with easy to hand-solder, 1206 footprints. This allows him to get a fairly random mix of colors in the completed ornament.

The LED array is pseudo-charlieplexed. One terminal of each LED goes to a GPIO pin on the micro-controller and the other terminal of all the LED’s are connected to a single complimentary pair of N-channel/P-channel MOSFETs — connected in totem-pole fashion. Depending on which MOSFET is switched on via a GPIO pin driving the gate pin high or low, the second terminal of each LED gets connected to either supply or ground. In combination with the GPIO pins being driven high/low, this allows the bi-color LED to be biased in either direction. Getting each LED to emit one color is simple enough — setting all LED GPIOs low, and MOSFET gate GPIO high will bias the LEDs in one direction. Reverse the GPIO logic, and the LEDs will be biased in the other direction. If this is done slow enough, the two colors can be differentiated easily. If the driving logic is made fast, changing states every 10us, the two separate colors merge to form a third hue. With some clever bit of code, he also adds some randomness in the GPIO output states, resulting in a more appealing twinkling effect. [Martin] does a detailed walk through in the video embedded below.

If you have the same bunch of parts lying around and wish to replicate the project, be warned that the KiCad source files will need some work to clean up errors — [Martin] was in a hurry and knew what he was doing so there are some intentional mistakes in the schematic such as using the same symbol for the N-channel and P-channel MOSFETs, and uni-directional LED symbol in place of the bi-directional one. And for programming, you will need one of these pricey pogo-pin style cables, unless you decide to edit the PCB before sending off the Gerbers.

[Martin] built just three of these bespoke ornaments, retaining one and giving away the other two to a neighbour and a co-worker. But if you would really like to build a tree ornament with addressable LEDs, then check out the Sierpinski Christmas Tree which can be cascaded to form an array of tree ornaments.

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Rheoscopic Holiday Ornaments

We had to look it up on Wikipedia – “Rheoscopic fluid means ‘current showing’ fluid. Such fluids are effective in visualizing dynamic currents in fluids, such as convection and laminar flow. They have microscopic crystalline platelets such as mica, metallic flakes, or fish scales, in suspension in a fluid such as water or glycol stearate.” And so it seems [Will Donaldson] has figured out a great way to Animate Christmas Ornaments using Rheoscopic Fluid, just in time for the holiday season.

Making the fluid is pretty simple, and uses just a few readily available materials – distilled water, rheoscopic fluid concentrate and your choice of food colouring. The hardware is dead simple too – clear, spherical baubles with lids and core-less DC motors such as used in mini and nano drones, to agitate the fluid. You can use cell phone vibration motors too, but [Will]’s experimentation suggests that the level of agitation is not a lot.

To make a bauble, you fill it with the fluid, hot glue the motor to the lid, close the lid such that the motor and its agitator are dunked in the fluid, and dab a generous amount of hot melt glue to seal it all shut. Then, hook it up to a suitable power supply and get enchanted by the mesmerising movements of the rheoscopic fluid in the bauble. The agitator is just a plain ol’ drone propeller forced in to a shape that is narrow enough to be pushed through the neck of the bauble. It’s a seasonal ornament, so don’t expect the motors to last long being submerged in the rheoscopic fluid. [Will]’s contraptions have not yet failed after a couple of days, and it may be safe to estimate that the motors may last about a week or two at most. Of course, YMMV depending on if you used distilled water or plain tap water and other factors.

As [Will] suggests, if you prefer slower swirls, or random agitation, then it’s best to hook up a micro-controller and motor driver for fancy effects. At this point, it may be tempting to think of embedding LED’s inside the baubles, but doing so reduces the rheoscopic effect since it relies on reflecting light shining on it from the outside. The video embedded after the break has all the build details.

It’s a great way to teach some science to the kids during the holidays and maybe even get them to help with the project. And don’t assume this is just a cheap Christmas trick. Artist Paul Matisse has invented an art device/technique based on rheoscopic fluids which he calls “Kalliroscope©”. He patented it in 1968, and has sold Kalliroscope artworks throughout the world since then. From his website “A Kalliroscope is a device for viewing fluid currents. Kalliroscopes are both works of art and intuitively educational displays of the scientific principles of fluid dynamics. They are glass and steel constructions containing a current-visualizing fluid.” We’re not sure how priceless those works of art are, but it’s safe to assume you need deep pockets to buy one. So go ahead, turn your Christmas Tree in to a work of Art !

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Teardown: AppLights Personalized Projection

Listen, it hurts to hear, but somebody needs to say it. It’s over, OK? You’ve got to admit it and move on. Sure, you could get away with it for a week or two in January, but now it’s just getting weird. No matter how hard you fight it, the facts are the facts: the holidays are over. It’s time to pack up all those lights and decorations before the neighbors really start talking.

Fun Fact: It can’t actually do this

But don’t worry, because there’s an upside. Retailers are now gearing up for their next big selling season, which means right now clearance racks the world over are likely to be playing home to holiday lights and decor. That wouldn’t have been very interesting to the average hacker or maker a few years ago, after all, there’s only so much you can do with a string of twinkle lights. But today, holiday decorations are dripping with the sort of high-tech features you’d expect from gadgets that are actively aiming to be obsolete within the next ten months or so.

Case in point, the “AppLights Personalized Projection” which I found sulking around the clearance section of the Home Depot a couple weeks back. This device advertises the ability to project multi-color custom messages and animations on your wall, and is configured over Bluetooth with a companion application on your Android or iOS device. At a minimum we can assume the device must contain a fairly powerful RGB LED, an LCD to shine the light through, and some sort of Bluetooth-compatible microcontroller. For $20 USD, I thought it was worth taking a shot on.

Around this time last year, the regular Hackaday reader may recall I did a teardown for a Christmas laser projector. Inside we found red, green, and blue lasers of considerable power, as well as all the optics and support hardware to get them running. It was a veritable laser playground for $14. Let’s see if the AppLights projector turns out to be a similar electronic cornucopia, and whether or not we’ve got a new Hackaday Holiday tradition on our hands.

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Christmas POV Display Makes Viewer Do The Work

Hackaday readers have certainly seen more than a few persistence of vision (POV) displays at this point, which usually take the form of a spinning LED array which needs to run up to a certain speed before the message becomes visible. The idea is that the LEDs rapidly blink out a part of the overall image, and when they get spinning fast enough your brain stitches the image together into something legible. It’s a fairly simple effect to pull off, but can look pretty neat if well executed.

But [Andy Doswell] has recently taken an interesting alternate approach to this common technique. Rather than an array of LEDs that spin or rock back and forth in front of the viewer, his version of the display doesn’t move at all. Instead it has the viewer do the work, truly making it the “Chad” of POV displays. As the viewer moves in front of the array, either on foot or in a vehicle, they’ll receive the appropriate Yuletide greeting.

In a blog post, [Andy] gives some high level details on the build. Made up of an Arduino, eight LEDs, and the appropriate current limiting resistors on a scrap piece of perfboard; the display is stuck on his window frame so anyone passing by the house can see it.

On the software side, the code is really an exercise in minimalism. The majority of the file is the static values for the LED states stored in an array, and the code simply loops through the array using PORTD to set the states of all eight digital pins at once. The simplicity of the code is another advantage of having the meatbag human viewer figure out the appropriate movement speed on their own.

This isn’t the only POV display we’ve seen with an interesting “hook” recently, proving there’s still room for innovation with the technology. A POV display that fits into a pen is certainly a solid piece of engineering, and there’s little debate the Dr Strange-style spellcaster is one of the coolest things anyone has ever seen. And don’t forget Dog-POV which estimates speed of travel by persisting different images.

[Thanks to Ian for the tip.]

Engineer’s Primer On DIY Christmas Light Shows

Each year brings new Christmas light shows, with synchronised music and wild blinking decorations to light your eyeballs ablaze. Now, many of us have dabbled in the dark arts of blinken, tinkering with LEDs or flashing a neon bulb or two. There’s plenty of tutorials on how to control all manner of lights, but they’re often written for novices. Learning the basics of electronics for the nth time when you just need to know the specifics of a protocol or what IC you need can be a total drag. That’s why [Bill Porter] has written the Engineer’s Guide to DIY Computer Controlled Holiday Lights.

[Bill] covers the topic from start to finish – not just the technical side of things, but practical considerations about where to source components, and timescales for keeping your project on track. It’s no coincidence this is coming out in January – if you want to get something big up and running for Christmas, it’s time to start now! The guide gives links to forum communities that put in large group orders for parts early, and ship them slow to save money.

Other areas covered include software for creating advanced sequences for your lighting setup, which allow you to map animations over your entire layout. There’s also tips on which controller hardware to use for incandescent lights and the now-ubiquitous WS2811 strings. Even better, [Bill] shares specific tips on how to avoid common problems like voltage drop over long pixel runs and communication issues.

It’s a testament to [Bill] and his experience – the guide is an excellent way to get right up to speed with the state of the art in DIY Christmas light shows, and will save you from all manner of pitfalls. If you need to build something big this year and don’t want to reinvent the wheel, this is for you.

It’s not the first time we’ve heard from [Bill] either – check out his stunning wedding invitations or his repair of a science museum exhibit.

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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Laser Projected Christmas Lights

It’s August, and of course that means that it’s time for retail stores to put up their Christmas decorations! But seriously, if you’re going to do better than the neighbors you need to start now. [Joey] already has his early start on the decorations, with a house-sized light show using LED strips and a laser projector that he built last Christmas.

What started off as a thought that it would be nice to hang a wreath over the garage soon turned into a laser projector that shows holiday-themed animations on the front of the house. The project also includes a few RGB LED strips which can match the colors displayed by the projector. The LEDs are powered from a custom-built supply that is controlled by a laptop, and the program that runs on the computer averages the colors from the video signal going to the projector which lights up the LED strips to match the projected image. This creates an interesting effect similar to some projects that feature home theater ambient lighting.

The only major problem [Joey] came across was having to account for the lasers’ motion in the projected patterns, which was causing the computer to read false values. This and a few other laser-related quirks were taken care of with a bit of programming to make sure the system was functioning properly. After that it was a simple matter of attaching the projector to the roof and zip-tying the LED strips to the eaves of the house.

The projector is weatherproof, has survived one harsh winter already, and can be up and running for any holiday. With Halloween right around the corner, this could be a great way to spice up some trick-or-treating. Check out the video after the break to see this setup in action.

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