Raspberry Pi Doorbell project which emails you a picture of whoever presses the button
Implementation of a Raspberry Pi doorbell with a proper electrical detection circuit. Many implementation just connect the Pi to the doorbell speaker which is electrically hazardous to the Pi GPIO inputs because the speaker voltage goes below ground (+/- about 0.5 to 1 volts). The circuit that is implemented here uses a diode to clip the negative voltage then charge a capacitor which turns on a transistor that provides a clean 0 to 3.3 volt negative edge to the GPIO pin to generate an interrupt.
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