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I am playing with a speaker and a microcontroller and in some documentation the speaker is called buzzer. The assistant told us that is a mistake and we are dealing with a speaker.
I am wondering what exactly is the difference between the two, where can I learn more about these kind of devices and if there are any other similar or not so similar devices that are able to output sound.
EDIT: What is the difference between a piezo buzzer and why isn't buzzer a tag but piezo-buzzer is a tag ?
A buzzer usually has an oscillating transistor circuit inside - to make the buzzing noise when voltage is applied, so it makes a tone.
Applying voltage to a speaker will not make a tone, so you'd need an external oscillating circuit (e.g. a 555, or transistor oscillator). A speaker can play all kinds of sounds, however due to its built in circuits, a buzzer may not be capable of playing tones other than its oscillator's tone.
Buzzers are usually piezo buzzers - based on a tiny bit of crystal inside. You can usually see a metallic flat surface there, with a larger box/circuit underneath for the built in oscillator circuit.
When someone is "buzzed" into the house, its with a relay (electro-mechanical) sound-maker.
A relay, wired as normally closed, but able to break the circuit, is a buzzer.
simulate this circuit – Schematic created using CircuitLab
Traditionally a buzzer was a device designed to make noise. Traditionally it would have been an electromechanical device. It would typically be supplied with DC and the oscillations would have been produced by an electromechanical process inside the buzzer.
A speaker was/is a device used to reproduce sound from an electric waveform with the sound coming out being at least a passable analogue of the signal going in.
However in more recent years the world has moved on. The relative cost of electronics in general and micro controllers in particular has dropped compared to the cost of electromechanics.
So nowadays instead of a traditional mechanical buzzer we often use "piezo sounders". These are something of a half-way house between the traditional buzzers and speakers. They are driven with an audio-frequency waveform, typically a square wave. That allows multiple tones for different types of alert and even allows playing crude music. However they are not designed to reproduce arbitrary audio with anything like reasonable accuracy.
Whether to class piezo sounders as "buzzers", "speakers" or neither is somewhat a matter of semantics.
I suspect the "mistake" is actually a case of your instructor disagreeing with whoever wrote the course material rather than a real mistake but without more detail it is hard to be sure.
The buzzer gets the operating voltage, mostly DC and outputs sound. It can be a combination of a speaker and an oscillator. The piezo sounders are thatlike buzzers. The speaker in the buzzer can be optimized for a single sound, no need to reproduce music.
In the good old days the buzzer was an electromechanical releay oscillator that was noisy enough without any speaker. The relay itself vibrated. For stronger voice the moving part of the relay can have quite large area. Surely those apparates are still available due their robustness. The relay was connected to break its supply voltage as soon as the relay had pulled. For example the horn in a car can well be thislike electromechanical buzzer.
The speaker needs AC audio signal that makes its membrane to move and produce the sound. The speaker must operate in wide frequency area to have any value.
Another purely electric noisemaker is a plasma arc in the air - the same is used for welding and in ultra high luminosity arc lamps. If the current is modulated with audio signal, it surely can be heard. The low mass of the plasma suggests a high maximum frequency. I have not seen any real devices in front of me, but searching "plasma tweeter" gives several hits.
Another type of noise maker is the Siren which uses a different technique...
Most modern sirens use two concentric cylinders, which have slots parallel to their length. The inner cylinder is rotated by a motor while the outer one remains stationary. As air under pressure flows out of the slots of the inner cylinder and then escapes through the slots of the outer cylinder, the flow is periodically interrupted, creating a VERY LOUD tone.
Buzzer is speaker which produce certain sound like "buzz" but it can't be use to play your favourite song because has inbuilt oscillator which produce same waveform repeatedly.... Speaker are transducer which produce sound for analogous waveform input into it.
SPEAKERS -------RUNS ON AC (Square wave, triangular wave ,etc.)
BUZZER -----------RUNS ON DC
No other things than speaker and buzzer are available which produces sound.
Another electromechanical noisemaking device is the chime door bell. Unlike the relay approach it uses a solenoid to much a clapper which then hits a chime bar. When the voltage is removed the solenoid returns by a springto hit a deifferent chime bar of a different pitch, producing the classic "ding-dong" noise.
Buzzers:
a) are triggered by a DC signal while speakers are driven by an AC sound signal.
b) produce a buzzing sound while speakers produce any sound
Buzzers are one of two types:
a) piezo buzzers that use the piezoelectric phenomenon to vibrate their membrane (the most common type and most efficient in audible dB per Watt)
b) magnetic buzzers that contain a tiny speaker but their wee membrane can only reproduce high pitch sounds (the least common type but with the smallest footprint)
More sound related electronic devices are beepers, sirens, ultrasonic transducers (have a look)
I don't know about the tag but probably because piezo buzzers are more common
Exists probability that you will got somewhere buzzer device with internal frequency generating circuit.
But most probably, you will got device, which just transforms electricity to sound waves.
For such devices, the most important features - are their resistance and loudness (when have comparable size/weight), and unfortunately, exists extreme difference of piezo vs electromagnetic speakers in these.
For resistance: most small electromagnetic speakers used in computers have resistance approximately 8 Ohm.
piezo buzzers are very differently, physically equivalents to serial connected capacitor and inductance, but for case of microcontroller (Arduino) could considered to equivalent of 100 Ohm resistor.
For loudness - electromagnetic speaker is magnitude loader than piezo.
Conclusion - in most cases, piezo could been directly connected to digital cmos outputs (for better safety, you could wire it with 150 Ohm current limiting resistor).
Electromagnetic speaker needs some source of high current, and sure, for higher quality sound this source should have linear characteristics, and most microcontrollers could not feed high current.
But in case of microcontroller, could been used some simple circuit, like transistor switch circuit (open collector transistor switch circuit).
And sure, in case of electromagnetic speaker, you should use some sort of DC current limiter, for example, attach capacitor between mc pin and transistor, or write program which will not feed speaker with constant current.
Update: for other interesting things, I remembered, that any transformer (or just any coil with ferromagnetic core), could output sound.
It's very common, when power transformers output high sound. For example most TV's output it. Usually this is not very loud, but in silent room could hear.
Also few times I have hear high sound from voltage stabilizer, when computer run some programs, because power supply of this computer does not have PFC :)
Few times I have hear ring of analog voltmeter, when used some high power device like welding machine.
Update: About coils with cores - remembered, noise is one of things, with which people making/using brushless electric motors struggle.
Because brushless motors are some combination of coils with cores, they output unwanted sounds. And in most cases, people used high frequency currents, so these motors output ultrasound, which people don't hear. In some cases, controller electronics could not make control currents with high enough frequency, and could been hear sounds like squeaks or even screams.
Believe or not, any DC motor can produce sound just like small speaker, (it has coil and magnet) when you connect him on place where speaker was, you attach wires ofc plus to plus, minus to minus, and that's it, but it also produce vibrations as well, but doesn't turning around, just vibrate in place, except in cases of wrongly connected amplifier circuits where + (positive wire) goes through speaker, some people (amateurs) do even that but it's wrong ..try it for a fun with some audio player or guitar amplifier. But the best place to use dc motor in some audio system is if you put it as a input inductor of Reverb Spring Tank for guitar amplifier, I did it but for some shorter period of time, until I tried much better options for rev. tank, now I use small speaker as input of tank and piezo buzzer as a output
