Pseudonymous manufacturer “The Sink God”, hereafter simply “Sink”, decided to look at what a Raspberry Pi single board computer was doing in a different way – by capturing electromagnetic interference in a solenoid and turning it into audio.
“I made a simple circuit that allows me to listen to electromagnetic interference produced by all sorts of electronic devices,” Sink explains of the project, “and in this case I thought it would be interesting to ‘use a Raspberry Pi with the ‘listening’ device on the board.”
This simple circuit: a solenoid connected to a Texas Instruments LM386 low voltage audio power amplifier. When the circuits of the Raspberry Pi do their job, they create electromagnetic interference in the solenoid – interference, which is amplified by the LM386 to produce audible sounds.
“I placed the solenoid on top of the board, as close as possible with only a small layer of plastic in between to prevent the solenoid’s metal casing from shorting out anything on the Pi,” says Sink. . “The output of the LM386 (+ ground) is connected to the microphone jack of my laptop.”
What exactly you mean depends on what the Raspberry Pi is doing: Sink has been running a range of workloads, from simply connecting and running the
htop system monitor to the bandwidth-intensive process of downloading software updates via
apt and even stress the CPU with the SysBench benchmark tool.
“What I want to do at some point is add an adjustable frequency divider and band pass filter to the circuit,” adds Sink, “to have better control over the audio output. This might help fine-tune specific sounds/components.
Sink’s full video is available on Youtube.