Microwave beeps are annoying, possible solutions

Many microwaves are programmed to beep after they stop and then continue beeping every minute or so.

The simple solution is to put a switch for turning off/on the beeper.

But most users want to hear only one beep and not beeps every minute.

To achieve this feature we can remove the buzzer and install our own notification circuit. It will take a “cooking finished” signal.

Such a signal can be obtained in several ways:

• A signal from the power supply of the turntable motor. When the power supply stops, it outputs a logical high at the output. Optocoupler can be used (the LED of the optocoupler can be powered by a circuit with a capacitor voltage divider and bridge rectifier if the motor is powered by AC).

• A signal from a circuit that “watches” for the word “End” on the display by measuring the voltages on key segments. If it detects a pattern resembling “End,” it outputs a logical high at the output.

• A signal from the relay's coil turning on/off the motor.

However, the problem with this approach is that the beeps caused by button presses will not be heard.

This can be solved by using a circuit that disables the original beeper only after an “End” signal is detected. In this way, two beepers are used: the original beeper controlled via a relay or MOSFET to disable it when needed, and a custom beeper that emits a single beep upon receiving the End signal.

Has anyone done something like this?