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Input: A DC Voltage
Output: Sound waves - a buzzing noise.

The DC buzzer often uses a piezoelectric disc to generate the sound.
It also contains an oscillator circuit the generate the AC signal needed to drive the piezoelectric disc.

Its main advantage is simplicity of use.

Its main disadvantage is lack of choice ofer the pitch of the buzz.

Buzzers and Sounders

• Top Row: Active sounders.
  • They generate their own sound.
  • These all need a DC power supply.
  • DC Driver / Buffer / Switch needed.
  • Left to right: Very loud - middling - middling - not so loud.
• Middle Row: Low power speakers.
  • Do not generate their own sound.
  • An audio power amplifier is needed to drive these.
  • A 64 ohm (left) and an 8 Ohm Speaker (right).
  • Pleasant sound quality.
• Bottom Row: Piezoelectric Sounders.
  • Do not generate their own sound.
  • These can be driven with a 555 Astable.
  • 2500 to 4500 Hz are typical frequencies.
  • Harsh sounding.
  • Very noticeable.

Sounders

These do not generate their own sound. A separate circuit like an Astable is needed. An audio power amplifier might be needed.

Buzzers

Buzzers convert a Direct Current into a buzzing noise. This can be anything from an unobtrusive warning sound to a deafening noise designed to be heard in very noisy environments.

Some are semi-mechanical. Others use an oscillator circuit to produce an AC signal. This is used to drive a transducer that converts the AC signals into sound energy.

In all cases the sound is produced by a vibrating surface that creates pressure waves in the air (sound).

The vibrating surface can be made of quartz, using the piezoelectric effect or a moving coil can vibrate a paper cone (a loudspeaker).

A bell is a special case. There is a vibrating clapper which strikes the bell.

Designing Sounder or Buzzer Drivers

1. How loud does it need to be? This is measured in dB, decibels with a sound level meter and it needs to be louder than the background environmental noise.
2. What voltage does it run on? Check out the data sheet. Test it with a multimeter.
3. Is AC or DC needed? Check out the data sheet.
4. How much current flows through the buzzer so what kind of transducer driver do you need? Measure the buzzer current with a multimeter.
5. Is the device inductive (does it use an electromagnet)? If so, the transducer driver circuit must be protected against Back EMF.