Hello friends! Today we will design and examine a buzzer circuit in Proteus ISIS. We will use a logic input, an optocoupler and a transistor to control a powered buzzer, then look at the changes needed before using the idea in hardware. A buzzer is useful for indicating a timer event, a button press or a fault. The first design decision is whether the selected sounder contains its own oscillator or requires an alternating drive signal. Applying DC works for an active buzzer, but does not produce a continuous tone from every passive transducer. The original simulation images remain in this tutorial. We will explain their active-low behavior while correcting several details that a simulation alone can hide, including LED current, transistor bias and optocoupler pin mapping. Figure: Historica ...