Piezo buzzer - do they all do all tones?

Other Hardware General Electronics
1

Hi,

I want to use a buzzer in a small project that will control a level crossing on a model railway. I would like a 2 tone buzzer.

It seems that the piezo buzzer should be fine, and using the tone() function will produce a whole range of tones.

However, when I look to buy a buzzer, the store lists them all as coming with a "drive" circuit, and also gives them a frequency rating - which would also be the resonant frequency.

My question is:

If I buy a "piezo buzzer" that comes with a rated frequency and [internal oscillator] drive circuit, can I still use it with the tone() to produce a range of sound?

Thanks.

2

No.
There are two types of buzzers.
Active (with drive circuit) and passive (piezo).
The flat ones are usually passive.
They can be used for different tones, and even music.
Leo..

3

I thought that a piezo device with no drive circuit is a sensor not a buzzer, although I may have that wrong.

4

I thought that a piezo device with no drive circuit is a sensor not a buzzer, although I may have that wrong.

It can work either way. Sensors are optimized to convert mechanical energy into electricity and speakers/transducers convert electricity to mechanical energy.

The same is true for dynamic speakers & microphones... Both are made with a movable coil around a magnet, connected to a diaphragm that either moves air or is moved by vibrations in the air.

[u]Here[/u] is a piezo tweeter designed for use in hi-fi speakers.

5

DVDdoug:
The same is true for dynamic speakers & microphones... Both are made with a movable coil around a magnet, connected to a diaphragm that either moves air or is moved by vibrations in the air.

Jeez, that takes me back 50 years. We had a portable radio (a "transistor") which had a mic plug on the side so you could use it as a cheap PA. My late Dad* hooked a small speaker to a jack plug and plugged it in so we could use that as a microphone. I thought that was some kind of voodoo until he explained it basically as you just did.

*No, he wasn't late then, but is now. :wink:

6

Thanks!

Still mildly confused, but is this correct:

This item will only ever make one tone, no matter what you output from the arduino, because it has an internal driver which does the oscillating

However, this item, called a transducer for some reason, is listed as "externally driven" and therefore up to me to drive, which would therefore work with arduino and tone()

?

7

The transducer link is most likely only the piezo element.
If so, it can be used for various tones/music.
It has a hole/resonating chamber, so it is louder at the resonating frequency.
So it could be used as a loud buzzer if you feed it with the right frequency.
If you want to play different tones, it might be better to remove the disc from it's plastic case and attach/glue it onto something flat.
You can also buy just the piezo disk with wires attached. Like this one.
Piezo discs can also be used as microphones, knock sensors, etc.
Leo..

8

Transducers transform energy from one form to another. Piezo transducers convert
mechanical energy to electrical and vice versa. Flat diaphragms of piezo flex and
act like speakers or microphones so convert sound energy to/from electrical.

Many sensors are also tranducers (photo diodes can emit light for instance). Some sensors
aren't transducers though (the Hall effect doesn't work in reverse for instance, nor can
Geiger counters work in reverse!)

9

Ah I see, like a motor/generator.

Thanks! I'll get a transducer and an element, as they're both pretty cheap and take it from there.