Wearable Light Organ

The beating heart of the Wearable Light Organ is the LM324 Quad Op-Amp – similar in design to the 555 timer we've used before. It, too, is bundled as an integrated circuit (IC), with 14 pins. And similar to the LM556 DIP-14 we used in the Whack-A-Mole, this chip actually contains four separate op-amps, each capable of producing a singular voltage output from a differential voltage input. You can see the pin ordering for each amp in this data sheet for the LM324. This project only requires two op-amps, or pins 1-3 & 5-7 (more on that in the Schematic Tips & Tricks section, below).

Watch it Turn Sound into Light

As with any electronics experiment, it's worthwhile to have a lab assistant beta test your projects. Check out this short and sweet video of Steve Hobley's daughter playing with the Wearable Light Organ. Our version of the organ is, of course, a quite simplified circuit design based on a much more complex idea. Original light organs from the 1970s had three colors, typically red, green, and blue. These colors corresponded to frequencies in bass, mid, and high. You can see a contemporary version of this more-sophisticated design in action in this video by Collin Cunningham for MAKE, which is AC powered, and uses audio input from a laptop to blink a bunch of LEDs.

Schematic Tips & Tricks

Even for an experienced maker it can get confusing working on a circuit board, constantly flipping the board over, turning it 90 degrees, and so on. One trick when assembling your board is to keep a paper printout of your circuit design handy, and scratch out each connection as you make them.

As noted above, the LM324 contains four separate op-amps, and we are using two of them. These are each indicated in our schematic by a symbol: a triangle on its side. Each op-amp appears connected to pin #4 – this pin is known as the common-collector voltage and is labeled in data sheets as "Vcc." If that seems confusing, remember that, like any learning curve, it takes some experimenting. Once you understand how the circuit as a whole operates, you'll better understand the individual components in relation to the whole.

The Challenge Continues

The Wearable Light Organ is now officially part of our Weekend Projects Challenge. Beyond simply building this project, we'd like to see someone actually implement the wearable aspect, perhaps even weaving the Light Organ into a costume for this weekend's most magnificent of maker holidays, Halloween!

As always, feel free to send us an email if you have any questions about any of our projects. Whether you need to mod them, confirm the function of a component, or scrap our design entirely and suggest a new one, we're here to help.