![]() ![]() Usually this is not very loud, but in silent room could hear.Īlso 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 :)įew times I have hear ring of analog voltmeter, when used some high power device like welding machine. It's very common, when power transformers output high sound. ![]() Update: for other interesting things, I remembered, that any transformer (or just any coil with ferromagnetic core), could output sound. 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.įor loudness - electromagnetic speaker is magnitude loader than piezo.Ĭonclusion - 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).Įlectromagnetic 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.īut in case of microcontroller, could been used some simple circuit, like transistor switch circuit (open collector transistor switch circuit).Īnd 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. 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.Įxists probability that you will got somewhere buzzer device with internal frequency generating circuit.īut most probably, you will got device, which just transforms electricity to sound waves.įor 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.įor resistance: most small electromagnetic speakers used in computers have resistance approximately 8 Ohm. Whether to class piezo sounders as "buzzers", "speakers" or neither is somewhat a matter of semantics. However they are not designed to reproduce arbitrary audio with anything like reasonable accuracy. That allows multiple tones for different types of alert and even allows playing crude music. They are driven with an audio-frequency waveform, typically a square wave. These are something of a half-way house between the traditional buzzers and speakers. So nowadays instead of a traditional mechanical buzzer we often use "piezo sounders". The relative cost of electronics in general and micro controllers in particular has dropped compared to the cost of electromechanics. However in more recent years the world has moved on. It would typically be supplied with DC and the oscillations would have been produced by an electromechanical process inside the buzzer.Ī 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. Traditionally it would have been an electromechanical device. Traditionally a buzzer was a device designed to make noise. ![]()
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