This 80's circuit, suggested in Texas Insrtruments documentation, uses a Hall effect sensor. The circuit triggers a 555 oscillator when the sensor is activated by a magnet, producing a sound on a piezo transducer.
This 80's circuit, suggested in Texas Insrtruments documentation, uses a Hall effect sensor. The circuit triggers a 555 oscillator when the sensor is activated by a magnet, producing a sound on a piezo transducer.