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What is a buzzer and how does it work

 

The word "buzzer" comes from the German "summen" - buzz. In essence, this is a sound-emitting device traditionally used as a signaling device. To date, buzzers are electromechanical and piezoelectric. Both that and others find application in different devices.

How does the buzzer work?

Historically, the first appeared electromechanical buzzer, which is an electromechanical relay with normally closed contacts, through which the coil of this relay is connected to a current source.

The principle of operation of the buzzer is simply impossible. When a current flows in the buzzer's working circuit, the relay coil is excited, which means that the magnetic flux in its core increases, under the influence of which the contacts through which the coil itself has just been fed open immediately.

When the contacts are opened, the relay winding ceases to receive power, the magnetic flux in the core disappears, which means that the movable contact that has just closed the relay power circuit is released, and the spring puts the circuit into its initially closed state.

And so, the contacts are again closed, the coil again receives power, and the core again attracts the movable relay contact, again breaking its own supply circuit. So the process repeats over and over. The vibrations of the relay arm make a humming sound. The Rumkorff coil works the same way.

The principle of operation of the electromechanical buzzer

Of course, in the course of its operation, the relay-based buzzer not only generates strong impulse noise in the power circuit, but also emits strong interference into the radio air, therefore, the buzzer is used, among other things, for testing various equipment for noise immunity.

The main drawback of the electromechanical buzzer is obvious: the presence of a movable element wears out the mechanism, and the spring weakens over time, and therefore the failure time of the buzzer is no more than 5000 hours.

However, the first use of the buzzer, invented by Johann Wagner in 1839, and later developed by John Mirand, who added a bell to the vibrating hammer, deserves attention. It turned out an electric bell, producing a sound by striking a bell with a hammer. The bell hammer was connected to the relay armature, which directly operated in the buzzer mode.

Electromagnetic doorbell

The first electric doorbells installed in all apartments were arranged approximately the same (see - Electric bell device) Fire alarm bells have the same device as the first bells hanging at train stations.

A more modern version of the buzzer is a piezoelectric sound emitter, related to electro-acoustic devices, and producing an audible sound or ultrasound using the inverse piezoelectric effect.

Piezoelectric sound emitter

A piezoelectric is deposited here on a thin metal plate. On the reverse side of the piezoelectric layer there is conductive spraying. Spraying and the plate itself are the contacts to which power is supplied. To enhance the amplitude of propagating sound vibrations, a small mouthpiece with a hole can be attached to the plate.

Piezoelectric buzzer for arduino

The piezoelectric buzzer is powered by alternating current at a voltage of 3 to 10 volts, and the current frequency determines the frequency of sound. The characteristic resonant frequency of piezoelectric sound emitters lies in the range from 1 to 4 kHz, which leads to an easily recognizable buzzing with sound pressure reaching 75 dB at a distance of 1 meter from the emitter. Such buzzers can work like microphones or sensors.

Piezoelectric buzzers are used in alarm clocks, toys, household appliances, and telephone sets.The ultrasound obtained with their help is often used in repellents against rodents, in humidifiers, in ultrasonic cleaning, etc.

See also at i.electricianexp.com:

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