3D Printable LED Diffusors

While you can get an LED matrix in any size or shape, the really cool looking ones that are perfect for low-res displays all have diffusors. When they come from a nameless Chinese factory, these diffusors are thin sheets of plastic set into an extruded plastic frame. Since [Jan] has a 3D printer, he figured a custom diffusor was just a few bits of filament and a SCAD file away.

The basis for this custom LED diffusor was a LoL Shield given to [Jan] by the creator at the recent 31C3 conference. This shield is really only just 126 LEDs, multiplexed and in an Arduino form factor, and that many LEDs were just too bright and indistinct next to each other. The plan for a 3D printed diffusor was hatched.

After taking a few measurements, a pair of OpenSCAD files were whipped up and printed out. Assembly consisted of pressing 126 tiny little white diffusors into a frame, but once everything was attached to the matrix, the results were worth it.

Check out the video below for the before and after, demonstrating what a few bits of plastic can do to a LED matrix.

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This Cake is Not a Lie

Introducing the world’s first(?) edible and interactive RGB matrix cake — the ArCake.

[Treibair], one of our readers from Germany was inspired a few years ago with the LED cake we made here at Hackaday. Ours used angel food cake squares that allowed LED lights to shine through the squares from underneath the cake, where the LEDs are housed in the technologically advanced cake tray. It worked pretty well but we didn’t exactly recommend people to follow in our foodsteps.

That didn’t stop [Treibair] though, and he came up with his own unique twist on the cake! Instead of bothering with various cubes of angel food cake, he had a much more direct method.

It’s easy to do, just follow these steps:

  • Drill some holes in a cake
  • Put your jello in that cake
  • Make her open the box

And that’s the way you do it.

The resultant LED diffusers let lots of light through, while retaining their most important quality — tastiness. All in all, he made 30 jello filled holes which allowed him to place a 5 x 6 LED matrix underneath the cake. Now when he gives the cake to his wife, it will read her a Happy Birthday message, and then allow her to play a Jump’n’Run game using a Wii nunchuck controller!

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Bike Rim Lighting Lets the Night Crowd Know When You’re Rollin’

There comes a wonderful “MacGyver moment” in many hackers’ lives when we find ourselves with just the right microcosm of scrap parts to build something awesome. That’s exactly what [dragonator] did with his gifted tech box from Instructables. He’s combined RGB LEDs, a Trinket, and a hall effect sensor to add a semicircular rainbow pattern to his night ride while he rides it.

The theory behind the hack is well-known: given the time between pings from a hall-effect sensor responding to the magnet on a bike wheel, an embedded system can estimate the wheel rpm and predict the time to display a particular color on the LEDs. [dragonator] uses the known wheel speed to determine the LED pattern currently on display: either a slow breathing pulse to a half-circle rainbow that displays on the lower bike rim. He drops in the needed equations and required components to follow his trail in a well-documented instructable.

Persistence of Vision (POV) is a nice extension from blinking your first (or first hundred) LED(s). It’s just enough math to get the casual onlooker to cry “magic” and just enough embedded electronics to get those seasoned double-Es to nod their heads. If you’re new to the POV crowd, [dragonator’s] Instructable may be a great start.

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Ambilight for your Piano (Hero)

That old upright piano still sounds great, and now it can easily have its own special effects. [DangerousTim] added LED strips which change color when he tickles the ivories. The strips are applied along the perimeter of the rear side of the upright causing the light to reflect off of the wall behind the instrument. This is a familiar orientation which is often seen in ambilight clone builds and will surely give you the thrill of Guitar Hero’s brightly changing graphics while you rock the [Jerry Lee Lewis].

Key to this build is the electret microphone and opamp which feed an Arduino. This allows the sound from the piano to be processed in order to affect the color and intensity of the LED strips. These are not addressable, but use a transistor to switch power to the three colors of all pixels simultaneously.

We think there’s room for some clever derivative builds, but we’re still scratching our heads as to how we’d use addressable pixels. Does anyone know a relatively easy way to take the mic input and reliably establish which keys are being played? If so, we can’t wait to see your ambilight-piano-clone build. Don’t forget to tip us off when you finish the hack!

RGB Bike Rim Lights

[Yvo] sent us his latest creation, this awesome POV RGB bicycle rim light build, which features a circular interweaving of common RGB LEDs that face outward along the rim as they display constantly changing animations based on the wheel’s rpm.

Like many POV wheel builds, [Yvo]’s takes advantage of a hall effect sensor and stationary magnet to determine how fast the wheels are spinning. Unlike most POV builds, however, [Yvo’s] creation doesn’t have just one or two RGB sticks clamped onto a spoke. Instead, his wheels boast several individual RGB LED modules mounted along the rim.

Each wheel has six modules, and each module contains a scratch-build LED controller (a daisy chain of 74HC595 shift registers) that fits into a custom-made 3D-printed enclosure. The enclosures mounts onto some aluminum strips along with the RGB LEDs, and the aluminum strips mount to the wheels by straddling the rim.

At speed, the lights go into POV mode to simulate headlights / brakes with white in the front and red in the back. Check out the difference these custom circular modules make when riding and when at rest in a video below.

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WiFi Lamp Challenge – 5 Hour Speedrun

“We want to get this done quick, not right.”

[CNLohr]’s favorite desk lamp broke, so he gave himself a challenge: convert the lamp to LED and control it via WiFi within 5 hours, from scratch. He video recorded and narrated the whole process and did a nice job of explaining the tricky parts and failures along the way, fast forwarding us through the slow parts.

Some bits and pieces were simple and obvious: gut the old bulb, wire some LEDs, add a few power resistors, toss in a power supply from “like a monitor or something, don’t care” for the LEDs, add in what looks like an LM2596 adjustable power supply for the logic, some kind of ATMega, that new ESP8266 (Wi07C), splice on a power cord, etc. Standard stuff.

To our readers who’s hacks tend to start with soldering irons and screwdrivers, the video shows harder parts of designing an electronics project: creating the PCB in software (he used KiCad), lithographically transferring the circuit to a PCB, bismuth solderpasting & populating the board, and writing and documenting his code on Github. Perhaps most reassuringly, he also showed the consequences of every greedy shortcut and the process of troubleshooting around them.

If you have ever tried to follow a recipe from a cooking show and noticed how easy it all seems when everything is measured and prepped beforehand – and then what a disaster it is when you try it – the same is revealed here. Overall, it is a very thorough demonstration of what it actually takes to design a project – not just perfect circuits and perfect steps to follow.

In the end he got it done in the nick of time an hour late because he cannot add. Close enough.

Thanks [gokkor] for the tip.

The Most Minimal WS2812B Driver

Whether you call them individually controllable RGB LEDs, WS2812, or NeoPixels, there’s no denying they are extremely popular and a staple of every glowey and blinkey project. Fresh off the reel, they’re nearly useless – you need a controller, and that has led to many people coming up with many different solutions to the same problem. Here’s another solution, notable because it’s the most minimal WS2812 driver we’ve ever seen.

The critical component in this build is NXP’s LPC810, an ARM Cortex M0+ in an 8-pin DIP package. Yes, it’s the only ARM in a DIP-8, but still able to run at 30MHz, and hold a 4kB program.

JeeLabs is using the SPI bus on the LPC810 to clock out data at the rate required by the LEDs. The only hardware required is a small LED to drop the voltage from 5V to 3.3V and a decoupling capacitor. Yes, you could easily get away with this as a one-component build.

The build consists of a ring of sixty WS2812b RGB LEDs, and the chip dutifully clocking out bits at the correct rate. It’s the perfect start to an LED clock project, an Iron Man arc reactor (are we still doing those?), or just random blinkey LEDs stuffed into a wearable.

Thanks [Martyn] for sending this one in.