Magnetic Resonance Amplifier: Supplement: Piezo Element, LED Flashes
Here’s a neat thing I discovered about these little piezo buzzer elements. I knew they would flash the LED, but evidently they also somehow hold enough charge so that they are able to flash it again when the element is short-circuited. This shows up fairly well in the slow-motion section at the end of the video. “Sorry about the light!”
The magnets in the arrangement here “pre-stress” the piezo element and make it more responsive to taps and vibrations, I think.