Color-Changing LED Makes Techno Music

As much as we like addressable LEDs for their obedience, why do we always have to control everything? At least participants of the MusicMaker Hacklab, which was part of the Artefact Festival in February this year, have learned, that sometimes we should just sit down with our electronics and listen.

With the end of the Artefact Festival approaching, they still had this leftover color-changing LED from an otherwise scavenged toy reverb microphone. When powered by a 9 V battery, the LED would start a tiny light show, flashing, fading and mixing the very best out of its three primary colors. Acoustically, however, it spent most of its time in silent dignity.

singing_led_led_anatomy

As you may know, this kind of LED contains a tiny integrated circuit. This IC pulse-width-modulates the current through the light-emitting junctions in preprogrammed patterns, thus creating the colorful light effects.

To give the LED a voice, the participants added a 1 kΩ series resistor to the LED’s “anode”, which effectively translates variations in the current passing through the LED into measurable variations of voltage. This signal could then be fed into a small speaker or a mixing console. The LED expressed its gratitude for the life-changing modification by chanting its very own disco song.

singing_led_hook_up_schematic

This particular IC seems to operate at a switching frequency of about 1.1 kHz and the resulting square wave signal noticeably dominates the mix. However, not everything we hear there may be explained solely by the PWM. There are those rhythmic “thump” noises, shifts in pitch and amplitude of the sound and more to analyze and learn from. Not wanting to spoil your fun of making sense of the beeps and cracks (feel free to spoil as much as you want in the comments!), we just say enjoy the video and thanks to the people of the STUK Belgium for sharing their findings.

25 thoughts on “Color-Changing LED Makes Techno Music

        1. I listened to it again and it seem that it’s in a big hall or something like that and there is a delay in the sound from the speakers.

          Which woman are you in the video?

    1. Most probably the “drum” effect is given from the internal switch full ON and/or OFF noise of the various diodes. The steep variation of the current required to lit from one LED to another or maybe to 3 of them, will provide an audio pulse since current step in DC is filtered away from the coupling AC capacitor on audio inputs, providing only the delta (the pulses) transalted in sound in correspondence of such current steps. The out-of-sync effect is because you expect the pulses to be in a different moment rather then they actually are.

      1. You’re right, the thumping sounds are from switches between constant current outputs – this LED switches between a fading mode (PWM) and a mode where it cycles rapidly between primary colors at full intensity (no PWM). I did a similar video with the same kind of LED a while back; you can hear a similar thumping sound. It will also modulate a 2nd LED in parallel as they starve one another for current:

    1. I suspected as much, thanks for the link. Saw one of those cheap dollar store types and I could swear that it was powered by ‘Jingle Bells’. And not subtly either! It flickered Like morse code. Probably just a low button cell.

    1. Was just thinking it’d be nice to be able to buy music in LED form, little 2-pin socket thing for the player, and you buy an LED with the music stored on it, encoded as MP3 or whatever.

  1. More art than actual function…but why introduce a little art into Hackaday.
    Specially about how to draw a beautiful Schematic. Seen over the years shematics from he*l. So ugly and text over lines and symbols. Text in different directions. Really like a 5 year old try doing a schematic.

  2. More art than actual function…but why NOT introduce a little art into Hackaday.
    Specially about how to draw a beautiful Schematic. Seen over the years shematics from he*l. So ugly and text over lines and symbols. Text in different directions. Really like a 5 year old try doing a schematic.

    Sorry, missed the not,
    Cooper

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