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Forum Index : Microcontroller and PC projects : PicoMite buzzer / beeper
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Mixtel90 Guru  Joined: 05/10/2019 Location: United KingdomPosts: 8300 |
There are two sorts of these, passive and active. Often they look very similar. Passive type - Small black cylinder These are similar to a small loudspeaker in operation. They have a low coil resistance and, like a loudspeaker, they have to be driven by a AC or pulse waveform to make any sound. Unlike a loudspeaker, they are designed to have a peak output at one particular frequency so you have to drive them at that to get maximum output. Note that these are inductive (requiring a reverse diode) and will always require a transistor or mosfet to drive them. Passive type - Flat disc These are a piezo element and are capacitive. Some need a relatively high drive voltage, but there are some which operate at around 5V. Like the above, they have to be drive by an oscillating waveform. Additionally they are quite quiet unless you bond them to a flat surface to act as a sounding board. They also have a "peaky" output. They don't require much current, but do need voltage. Active type - Small black cylinder These contain a small oscillator and a piezo element. They are self contained - apply a voltage and they beep at a fixed frequency. They may require a driver transistor in some cases. These are usually rated at a minimum of 5V, but some will work at 3.3V. GUI BEEP uses an active type. It produces an output pulse on a pin, as does PULSE. You can also use PLAY TONE for a passive type if you use the correct frequency (not critical) and a suitable driver transistor. Note that this isn't triggered by the GUI, you have to handle it separately. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| astroboy Regular Member  Joined: 28/12/2014 Location: AustraliaPosts: 41 |
Thanks Mick. I found this really helpful. |
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| k2backhoe Regular Member Joined: 04/12/2021 Location: United StatesPosts: 47 |
Thank you also. I find these kinds of concise and complete explanations extremely helpful! |
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