Automatic Door Bell Timer

The project allows a user to turn OFF the buzzer or bell for 10 hours to prevent annoyance from unexpected doorbell ring when falling asleep.

The doorbell circuit contains a resettable timer which is connected to 18V to 24V. The timer can be set by just pushing the button momentarily and the amber LED will come ON when the button is released which will disable the doorbell circuit for 10 hour period. The doorbell will be enabled when the amber LED goes OFF at the end of the 10 hour period and this cycle repeats every 24 hours. The crystal oscillator is used to set the timing which can last for months or years without needing to reset. The timer can be bypassed by using a toggle switch in cases when the doorbell is desired to operate for 24 hours or in the event of failure.

The ATtiny12 is the heart of the circuit which can be programmed to time 24 hour cycles. Along with the MCU as timer are the power supply, a capacitor back-up circuit, solid state relay circuit to switch the AC voltage in the doorbell circuit, and two indicator LEDs.

Rest of the project