LED Hacks

1862 Articles

There Once Was An IC Dedicated To Blinking An LED

January 4, 2018 by 56 Comments

Today you can buy flashing LEDs; a simple two-lead component that requires only a power supply to produce even flashes of light. They look for all the world like any other LED, though embedded in the plastic dome is an integrated circuit to do all that flashing work.

There was a time though when a flashing LED was something of a big deal, so much so that National Semiconductor produced a dedicated chip for the task. The LM3909 boasted the ability to flash an LED for over a year using a single C battery. That part is now long out of production, so [Dillon] has implemented the LM3909 circuit using discrete components on a small PCB designed to take pins and fit the footprint of the original.

Why on earth might a reborn LM3909 be of interest to him, you ask? Well, he wasn’t able to make a 555 flash the LED from a coin cell, and a friend mentioned this chip which piqued his interest. The internal schematic is in the data sheet (found in the files section of his project), so he was able to implement it relatively easily using common parts. It still requires an external capacitor just like the original, but there is space on-board should you wish to put it there.

He’s produced a video we’ve placed below the break showing the device in action, proving it to be a drop-in replacement for an original. Recreations of classic chips using discretes are nothing new, we recently brought you a reborn PSU regulator chip made in 2014. An while you’re playing around with coin cell batteries, may we direct your attention to the Coin Cell Challenge.

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LED Fabrication From Wafer To Light

January 2, 2018 by 19 Comments

Building a circuit to blink an LED is the hardware world’s version of the venerable “Hello, world!” program — it teaches you the basics in a friendly, approachable way. And the blinky light project remains a valuable teaching tool right up through the hardware wizard level, provided you build your own LEDs first.

For [emach1ne], the DIY LED was part of a Master’s degree course and began with a slice of epitaxial wafer that goes through cleaning, annealing, and acid etching steps in preparation for photolithography. While gingerly handling some expensive masks, [emach1ne] got to use some really cool tools and processes — mask aligners, plasma etchers, and electron beam vapor deposition. [emach1ne] details every step that led to a nursery of baby LEDs on the wafer, each of which was tested. Working arrays were cut from the wafer and mounted in a lead frame, bonded with gold wires, and fiat lux.

The whole thing must have been a great experience in modern fab methods, and [emach1ne] should feel lucky to have access to tools like these. But if you think you can’t build your own semiconductor fab, we beg to differ.

[via r/engineering]

Programmable Christmas Tree Is A JavaScript Interpreter

December 24, 2017 by 4 Comments

Here at Hackaday, we find Christmas time very exciting because it means an influx of holiday-themed hacks that really help us get into the festive mood. [Andrew’s] programmable Christmas tree hosted at HackMyXmas is certainly one of our favorites. The project consists of a 500 RGB LEDs wrapped around a typical Christmas tree and controlled by a Teensy.  However, not settling for the typical, simple and cyclical pattern for the LEDs, [Andrew] decided the tree had to be programmable of course! So, a single board computer (a C.H.I.P) running Linux was used to provide a Wifi connection and a web server to easily program the tree.

This is where things get very interesting. The C.H.I.P board hosts a comprehensive website that conveniently gives you the option to program the LEDs using either, Scratch like draggable blocks (using Googles Blockly) or even pure JavaScript. Once the perfect pattern is conceived, you can test run it on the online simulator or even send it off straight to the Tree, watching it blink in all its glory on the provided live stream.

We applaud [Andrew] mammoth effort for invoking programming in such a fun way! You can check out the live stream of [Andrew]’s Christmas tree below.

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LED Christmas Tree Is Perfect Holiday Build

December 24, 2017 by 4 Comments

Soon the most wonderful time of the year will be upon us. Families all over the globe will gather together to exchange gifts, eat good food and enjoy some quality time with each other. For many, it will be the first time they’ve seen each other since the last holiday season. For us hackers –  this translates to a time we get to talk about ourselves and show off a little about what we do. Been taking it easy this year? Have no hacks to talk about? Well, it’s not too late! Break out the soldering iron and whip up the perfect conversation starter – an LED Christmas tree!

[Gumix] took a handful of those flickering LEDs and a step down DC-DC converter to make his simple but elegant tree. No microcontroller here… no code is running. As soon as power is applied, the flickering LEDs do all the work to create a visual delight.

Flickering LEDs have been the focus of a few hackers. They’re basically LEDs designed to flicker like a real candle. [cpldcpu] hooked a scope to one and guessed that a linear shift-register was responsible for the randomness behind the flickering, which would be confirmed several months later.

Be sure to check out [Gumix] LED tree and the video demonstration below.

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POV Display Is FAN-tastic

December 23, 2017 by 13 Comments

Persistence-of-vision displays come in all shapes and sizes. But when you get a couple of [Bruce Land’s] students involved, well let’s just say they tend to up the ante. When [Emily] and [Han] decided to make a POV display for their next class project, they did so with style. Unsatisfied with smaller displays they saw on YouTube – they decided to make a larger one out of an old box fan and a DotStar LED strip, which are similar to NeoPixels except they use SPI, which means you can update the LEDs at a much faster rate. This makes them perfect for a POV display!

As usual with projects out of Cornell’s EE class – this POV project is extremely well documented and it’s nice to see the fundamental details of a POV display explained. So be sure to check out this project if you’re rusty on the inner workings of POV displays.

We’ve seen some interesting POV displays here at Hackaday, including one strapped to a dog to display its running speed. What’s the coolest POV display you’ve seen?

Joule Thief Steals In Favor Of Christmas

December 22, 2017 by 14 Comments

A lot of things tend to get stretched during the holiday season, like shopping budgets and waistbands and patience. This year, [Chris] is stretching the limits of both the mini breadboard and the humble 1.5 V LR44 coin cell with his joule thief-driven LED mini Christmas tree.

With the push of a micro momentary, the joule thief circuit squeezes enough power from an LR44 to boot an MSP430 microcontroller, which needs 1.8 V – 3.6 V. After boot, the micro takes control of the joule thief circuit and milks it whenever the voltage falls below 3.2 V. This tree may be small in stature, but it’s feature-rich. A push of the same momentary button cycles through four different light shows, ending with a medley of all four. Be dazzled after the break.

The code for this tiny tree, which features an awesome ASCII breadboard layout and schematic, is up on GitHub. [Chris] has it listed among a few other manageable bare-metal ‘430 projects that would be great for beginners at pure C. If that sounds like you, why not give yourself the gift of learning a new language?

We’ve seen some spirited ways of lighting LEDs, but doing it with candle power takes the fruitcake.

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Bringing A Christmas Lights Show Inside

December 21, 2017 by 15 Comments

Instructables user [Osprey22] has been building towards this Christmas for years. Why? This year, he has brought an impressive musical Christmas light display inside, and at a fraction of the cost too!

An box at the tree’s base hides the power supply and the controller boards — a Raspberry Pi and a SanDevices e682 Pixel controller for the 400 WS2811 RGB LEDs — with an added router to connect them to the main network. The Pi is running Falcon Pi Player and a projector somewhere in the region of $100 complements the light show.

As far as mapping out the LEDs, Xlights is the program of choice, locating the LEDs in space with the help of a cell phone video recording. [Osprey22] had to write a quick program in C to fix the LED overlaps in the grid. (A spreadsheet would work just as well, here). Oh, and the gifts at the bottom of the tree double as a projector screen!

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