The control circuit triggers a solenoid that provides the kinetic movement for the sculpture. The circuit breaks down into the following stages:

  • a hall-effect sensor detects a neodymium magnet in the ball
  • falling edge detection with a PNP inverter (Q1) generates a pulse when edge detected
  • the falling edge pulse triggers a 555 timer configured for monostable operation
  • the 555 timer's threshold input is normally pulled low (R6), and a diode (D1) is included to absorb the opposite edge pulse.
  • a 50kΩ pot (R2) adjusts the monostable output pulse width
  • 555 output is active-low, so is used for PNP (Q2) high-side switching of the solenoid and indicator LED
  • a diode (D2) provides flyback protection from the solenoid

The adjustable output pulse allows it to be set at an appropriate length to fully activate the solenoid with out it remaining on too long.

All the details of the design and how it works are available in the project's GitHub Repo . Here's a little demo: