Passive means you make the wave
A passive buzzer has no oscillator inside. It sounds only while something outside pulls its coil on and off, so the sketch makes the wave and chooses the pitch. Held HIGH it clicks once and goes silent, with the coil still drawing about 200 mA.
Passive and active
Two kinds of buzzer look alike and are wired alike, and they want opposite things from your pin.
An active buzzer has a small oscillator circuit inside it. Give it power, a steady HIGH on its input, and it makes its own wave and beeps at the one pitch it was built for. The Active Buzzer block is one.
A passive buzzer, this one, has no circuit inside: only the coil and the disc. It makes a sound only while something outside switches the coil on and off, and whatever does that switching chooses the pitch. Here that is your sketch.
HIGH is silent
A steady HIGH turns the transistor on and leaves it on. The coil pulls the disc in, you hear one click, and then nothing moves. The only thing still happening is the coil's current: with nothing but its 16 Ω to limit it, about 200 mA from a 3.3 V supply and about 300 mA from 5 V. That is worked out from the datasheet's resistance, not measured, and it is two or three times what the buzzer is rated for while playing.
So a sketch for this block never leaves SIGNAL HIGH. When it wants silence it
writes LOW, or calls noTone(), which does the same.
The LED makes the mistake visible: it lights fully and stays lit.
A wave is a sound
tone(pin, 2700) puts a square wave on the pin, HIGH for half of each cycle
and LOW for the other half, 2700 times a second. The coil pulls the disc in
on each HIGH and lets it go on each LOW, and the disc moving 2700 times a
second is a 2700 Hz tone.
Change the number and the pitch changes. 440 is the A orchestras tune to; 262 is middle C. Any whole number of hertz the board can produce is a note this buzzer will play, and where it is loudest is the only thing that varies.
When it does not work
That is a passive buzzer doing what it should. HIGH pulls the disc in once and holds it, and a held disc makes no sound. Use tone(pin, frequency) to make the wave, and write the pin LOW, or call noTone(), when you want silence.
An active buzzer sketch sets the pin HIGH for sound and LOW for silence. On this block that gives a click and then silence, with the LED lit and the coil drawing current. Replace each HIGH with tone(pin, 2700) and each LOW with noTone(pin).
Yes, if the sketch changes as above. It is the more flexible of the two: an active buzzer has one pitch, this one plays any pitch you send it.
Where the coil's current comes from, and where it goes when the transistor lets go.
The transistor and the diode →Edit this page — content/books/passive-buzzer/passive-means-you-make-the-wave.mdx
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