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Eirik Brandal's cwymriad Is an ESP32-Powered Ring-Modulated Sound and Light Show Sculpture

Eirik Brandal's cwymriad Is an ESP32-Powered Ring-Modulated Sound and Light Show Sculpture


Maker Eirik Brandal has put together a circuit sculpture, dubbed cwymriad, which combines sound and light to visualize ring-modulated audio generated by an Espressif ESP32 microcontroller — a follow-up to the earlier audio-only ioalieia and maze-like ddrysfeöd.

"'Cwymriad' is based on a dual ring modulation circuit in which the ESP32 creates both the carrier and modulation signals," Brandal explains of his latest creation. "The square wave output of the ESP is filtered down to something resembling a triangle wave and combined in the ring modulator before the resulting signal is sent through an echo effect, and then sent back to the ESP32's internal ADC so that it can be displayed on the LED matrix."

Like his previous projects, the sculpture is put together with components floating in mid-air — suspended on wires that double as the circuit traces themselves. It's not a wholly free-form circuit sculpture, however: Key components, including the LED matrix and the speaker, are housed in or mounted on acrylic.

The cwymriad sculpture — Welsh for "collapse" — isn't Brandal's first venture into microcontroller-driven audio projects: Its direct precursor was ddrysfeöd — maze — which lights up sections of a labyrinth in time to the generated music. Ioalieia, meanwhile, had no visual element — but does represented Brandal's first go at building a speaker enclosure. "I didn't have high hopes for it," he writes, "and was expecting it to have a much sharper resonance frequency, but it turned out fine.

"I'm using an MCP4251 digital potentiometer to function as a sort of voltage controlled amplifier, except that the control voltage envelope is created in the code of the ESP and transferred to the digital pot via SPI," Brandal writes of his latest build

"Ring modulation in itself is of course quite similar to amplitude modulation, but here the digital pot is doing the volume control, while the ring modulator is creating the bell-like sounds out of only a couple of oscillators. I'm using a PT2399 echo chip to give some depth to the sound, and the whole thing is amplified by two bridged LM380 chips, while the LED matrix is driven by a few MAX7219s."

More details on the build, including a schematic, are available on Brandal's project page.

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