1

Buzzers

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Introduction

Purpose

To provide an overview of CUI Inc buzzers

Objectives

• Introduce the two main buzzer technologies and their working principles

• Introduce the two major circuit types their working principles

• Introduce various options among CUI’s buzzer line, including available sound effects and mounting types

• Define common specifications

• Introduce typical applicationsContent: 19 pages

Learning Time: 20

minutes

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Usage

Typical Usage

• Identification Signal

• Alarm

Home Appliances

• Safety and Security

• Automotive Electronics

• Office Automation

• Medical Equipment

• Industrial

• Consumer Electronics

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Piezo vs. Magnetic Buzzers

Piezo Buzzers

• Wide operating voltage: 3–250V

• Lower current consumption: less than 30mA

• Higher rated frequency

• Larger footprint

• Higher sound pressure level

Magnetic Buzzers

• Narrow operating voltage : 1–16V

• Higher current consumption : 30–100mA

• Lower rated frequency

• Smaller footprint

• Lower sound pressure level

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Piezoelectric Element

Structure of a Piezoceramic Element

With Feedback typeWithout Feedback type

Adhesive

ElectrodePiezoelectricCeramics

Metal PlateFeedback Electrode

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Working Principle

Vibration creates sound wave

Extended State

Compressed State

A.C. Voltage Applied

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Piezo Buzzer Structure

Transducer (without driving circuitry)

Indicator (with driving circuitry)

Terminal

Casing Piezoceramic Element

CasingPiezoceramic Element

Terminal

Circuit Board

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Feedback

• The feedback line provides a voltage that is proportional to the strain on the main piezo element.

• This voltage can be used to create a simple, self-oscillating, circuit.

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Magnetic Buzzers

Structure of Magnetic Buzzer

No Name of Parts

1 Casing

2 Vibrating Weight

3 Cavity

4 Vibrating Disk

5 Magnet

6 Pole

7 Coil

8 Yoke Plate

9 PCB

10 Transistor

11 Epoxy

12 Pin

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Working Principle

Vibrating disk

Magnet CoilPole Yoke Plate

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Indicators vs. Transducers

Indicators

• Built-in driving circuit

• Simple to design-in

• Fixed frequency

Transducers

• External driving circuit required

• Complex to design-in

• User-selected frequency

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Key Specifications

Frequency response The response of the system to an input with a constant amplitude but a varying frequency.

Sound pressure level (Unit: dB Pa)Sound pressure level, SPL, is the deviation from atmospheric pressure caused by the soundwave expressed in decibel Pascals. It is generally proportional to input voltage and decays by 6 dB’s when doubling the distance from the buzzer.

Resonant Frequency (Unit: Hz)Systems which vibrate have a frequency which they naturally tend to vibrate at. This is called the resonant frequency.

Impedance (Unit: ohm)Electrical impedance is the ratio of applied voltage to current.  The electrical impedance varies with frequency.

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dB’s

• dB stands for decibel.

• It is not a unit, but rather a numeric scale.

• Values increase exponentially, instead of linearly as in counting numbers.

• Expressed in “normal” numbers, 2 dB is ten times 1 dB.

• Allows for a huge range of values to be expressed in relatively little space.

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Frequency Response

• A perfect audio transducer would recreate every frequency without attenuation or gain. There is no perfect transducer.

• Frequency response is a quantitative measurement of a device’s ability to recreate any frequency.

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The Human Ear and A-Weighting

• Generally, most humans can perceive frequencies from 20–20,000 Hz.

• However, the human ear is more sensitive to some frequencies than others.

• A-weighting places more value on frequencies which the human ear is more sensitive to.

• Some CUI buzzers specify SPL using the A-weight system. I.E. dB A

Comparison of Different SPL’s

Jet engine at 30 m

632 Pa 150 dB

Threshold of pain 63.2 130 dB

Hearing damage (possible) 20 Pa Approx. 120 dB

Jet at 100 m 6.32–200 Pa 110–140 db

Jack hammer at 1 m 2 Pa Approx. 100 dB

Traffic on a busy roadway at 10 m

2x10-1–6.32x10-1 Pa 80–90 dB

Passenger car at 10 m 2x10-2–210-1 Pa 60–80 dB

Normal conversation at 1 m 2x10-3–2x10-2 Pa 40–60 dB

Very calm room 2x10-4–6.32x10-4 Pa 20–30 dB

Auditory threshold at 1kHz 2x10-5 Pa (RMS) 0 dB

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Resonant Frequency

• The natural frequency a system tends to oscillate at.

• Driving a system at its resonant frequency will create the largest amplitudes with the smallest input.

• Buzzers are loudest when driven at their resonant frequency.

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Sound Effects

• A buzzer is usually used as a warning sound, i.e. car security, car reverse aid, home appliances, medical instruments, industrial equipments, notebook, camera, and etc.

• Sound Effects: click the sound icon to test the different sounds.

Continuous (Feedback/ Warning Signal)

High/Low Tone (Warning Signal)

Slow/Fast Pulse (Feedback/ Warning Signal)

Siren (Alarm)

Chime (Door Bell)

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Mounting Configurations

Surface mount PCB mount

Wire leadsVertical mount

Panel mount

Wire leads w/flange

Snap-in

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Applications

HomeAppliances

Automotive Medical

Security

Industrial Office Automation

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Summary

• CUI Inc’s buzzers are used across a range of applications as indicators and alerts

• Two main technologies are used to generate sounds: magnetic and piezoelectric

• Indicators include a built-in driving circuit while transducers require and external source to create a tone

• View CUI’s buzzer product offering