Buzzer

Buzzer is a sound generator or somewhat a bell you can say. It is to warn the person that something happened and you should give attention. The buzzers are used as door bells or sometimes they are uses with machines to give warning to the operator or in vehicles and they are providing warning to drivers about some action to be taken as something is going wrong. Like if a driver is not fastening his or her seat belt, a warning buzzer is sounding. If a driver is crossing the allowable speed limit for his or her vehicle, a buzzer is sounding and informing him or her to reduce the speed to the safe speed limit.

Typical buzzer arrangement and its function diagram

Most buzzers are very small and they are electromagnetic devices. Sometimes they are piezo electric devices. In autos they are located in dashboards or in the meter clusters to warn the driver about certain conditions. They are usually powered by ecu or engine control unit.

Buzzers have same like construction like a relay. But in buzzer the power applied to the buzzer electromagnetic coil is applied through its nc or normally closed contracts. At rest, no power is applied to the buzzer and its nc contacts are closed together. The current can pass through the contacts and can be applied to the buzzer coil. Then when power is applied to the coil, the armature or diaphragm is attracted towards the buzzer coil due to its electromagnetism. But the at that time the nc contacts opens and current path disconnects to the buzzer coil. At this moment the armature of the buzzer if retracted due to spring attached to it. The NC contacts close again and the same cycle repeated again. This all is happening very fast. The armature in this case is a diaphragm which produces a sound. That sound is warning the person.