this is a recap of the ledB project

  • 1 x resistor 10K thruhole
  • 1 x resistor 10M thruhole
  • 1 x diode BA159 or alternative
  • 1 x piezo disk ~3.5Khz (datasheet)
  • 1 x BLUE led (3.5v fwd voltagedatasheet)
  • 1 x LM741 opAmpo (datasheet)
  • 2 x coin cell battery CR2032

simulation

source