Sounding The Humble LED

Here at Hackaday we’re no strangers to the colorful glow of LEDs. But what if there was more to appreciate beneath the surface? Back in 2011 [Windell] over at Evil Mad Scientist dug into a certain variety of LED and discovered they had a song to sing.

Over the last couple decades, you’ve likely encountered the flickering “candle flame” variety of LED. Often found embedded in small plastic candle simulacra they are shaped like typical through hole “gumdrop” style LEDs, but pack some extra magic which causes them to flicker erratically. Coupled with a warm white color temperature the effect isn’t entirely dissimilar to the flickering of a candle flame.

To the Hackaday reader (and [Windell]) the cause of the flickering may be fairly clear, there is an IC embedded in the lens of the LED. See photo at top for an example of how this might look, helpfully magnified by the lens of the LED itself. Looking through the lens the captive die is visible, as well as the bond wires connecting it to the legs and light emitting diode itself. [Windell]’s observation is that together this assembly makes for a somewhat strange electrical component; from the perspective of the circuit it appears to randomly vary the current flowing through the LED.

He includes two interesting demos. One is that by attaching the flickering LED to a BJT he can turn it into a current amplifier and successfully drive a much more powerful 1W LED with the same effect. The other is that  with the power of the amplifier the same flickering LED can drive a buzzer as well. The effect is surprisingly pleasant, though we’d hesitate to call it musical.

For a more recent example of a similar phenomenon with a very different sound, check out out [Emily Velasco]’s playback of a similarly constructed RGB color changing LED, embedded below. We’ve seen optical tools used to decode LED flickers into data streams, but not for audio playback! We have also covered some LED flicker reverse engineering that spills more of the mystery sealed up in these specialized diodes.

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Freeforming The Atari Punk Console

This stunning piece of art is [Emily Velasco’s] take on the Atari Punk Console. It’s a freeform circuit that synthesizes sound using 555 timers. The circuit has been around for a long time, but her fabrication is completely new and simply incredible!

This isn’t [Emily’s] first rodeo. She previously built the mini CRT sculpture project seen to the left in the image above. Its centerpiece is a tiny CRT from an old video camera viewfinder, and it is fairly common for the driver circuit to understand composite video. And unlike CRTs, small video cameras with composite video output are easily available today for not much money. Together they bring a piece of 1980s-era video equipment into the modern selfie age. The cubic frame holding everything together is also the ground plane, but its main purpose is to give us an unimpeded view. We can admire the detail on this CRT and its accompanying circuitry representing 1982 state of the art in miniaturized consumer electronics. (And yes, high voltage components are safely insulated. Just don’t poke your finger under anything.)

With the experience gained from building that electrically simple brass frame, [Emily] then stepped up the difficulty for her follow-up project. It started with a sound synthesizer circuit built around a pair of 555 timers, popularized in the 1980s and nicknamed the Atari Punk Console. Since APC is a popular circuit found in several other Hackaday-featured projects, [Emily] decided she needed to add something else to stand out. Thus in addition to building her circuit in three-dimensional brass, two photocells were incorporated to give it rudimentary vision into its environment. Stimulus for this now light-sensitive APC were provided in the form of a RGB LED. One with a self-contained circuit to cycle through various colors and blinking patterns.

These two projects neatly bookend the range of roles brass rods can take in your own creations. From a simple frame that stays out of the way to being the central nervous system. While our Circuit Sculpture Contest judges may put emphasis the latter, both are equally valid ways to present something that is aesthetic in addition to being functional. Brass, copper, and wood are a refreshing change of pace from our standard materials of 3D-printed plastic and FR4 PCB. Go forth and explore what you can do!

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LED Christmas Tree Is Perfect Holiday Build

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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Blowing Out A Candle Flicker LED: The Death Of Flame

One day there will be no more need for flames. [slider2732] has put yet another nail in the coffin of this most ancient of all technology by making a candle that uses a flicker LED that you blow out. A little more miniaturization and we’ll have them fully integrated into the size of birthday cake candles (Hint hint, hackers!).

You may have seen these candle flicker LEDs.  They have a small chip inside them that modulates the LED’s light to flicker like a candle. We’ve even reported on what [Cpldcpu] found when he reverse engineered them first here and then here.

What [slider2732] did was to buy an electronic candle that used one of the LEDs actually shaped like a flame, and to drill a hole near the ‘flame’. He them embedded a microphone behind the hole. That goes to an LM386 amplifier circuit and from there to an Arduino Pro Mini all powered by a LiPo. As you’d expect, the Arduino code is very simple, just watch the pin from the amplifier and based on an internal variable, turn the LED on or off. We really like how none of the electronics is visible and how you actually have to lean over and blow into the top of the candle to blow it out. You can see this demonstrated in the video below.

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