Sound-Activated and Wearable Light Organ

About the size of two 9V batteries, and powered by only one, our latest Weekend Project, the Light Organ, is both portable and fun! The beating heart of this project is the LM324 Integrated Circuit (IC), the black chip in the middle of the board. This legendary IC actually has four operational amplifiers (or “op-amps”) embedded in it, although for the purpose of this project, we’re only using two. Converting sound into light via the condenser mic element (the round component at the bottom of the board), this project is reminiscent of light organs from the 1970s. Still confused? Check out the video below to see the Light Organ in action and I guarantee you’ll go “Aha!”

This is another super-simple Weekend Projects circuit design but I admit the four-amps-in-one aspect of the LM324 might seem confusing at first. This Texas Instrument data sheet [PDF] on the LM324 might help clarify some questions. On the first page, you can see the pin orientation. Each op-amp is numbered counter-clockwise starting from the top-left of the IC. So op-amp #1 is 1OUT, 1IN-, and 1IN+, and so forth for each op-amp. As noted. we’re only using two amps in this circuit, or pins 1-3 and 5-7. Pins 4 & 11 are also used as our IC’s power pins, operating as the common-collector voltage and GND, respectively.

If you have any further questions about this circuit design you can always feel free to email us. And of course all these tips & tricks, pointers and other makers’ builds are highlighted in our Weekend Projects Newsletter, so if you’re not already subscribed, sign up below!

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