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I am looking for a small, low power buzzer for my circuit. The components I found in the market do not fit my requirements. The piezo buzzers are too big (min diameter 9mm) while the electromagnetic one consume too much power.

Is there any other type of buzzer I can use? What is used in wristwatches?

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  • \$\begingroup\$ Do you have a link to the buzzers that are too big? What is your maximum allowable size? \$\endgroup\$ May 30, 2012 at 6:23
  • \$\begingroup\$ Do you have a link to the electromagnetic sounder that consumes too much power? What is your maximum allowable power level? And, on a related note, how much sound pressure/volume do you need: Are you building a warning buzzer or an in-ear headphone? \$\endgroup\$ May 30, 2012 at 19:31
  • \$\begingroup\$ You need 1x1mm MEMS speaker! Kidding, they are not yet invented. But that the only thing fit to your requirements. \$\endgroup\$
    – user924
    May 31, 2012 at 1:26
  • \$\begingroup\$ if you would ever return here: don't hit and run. If your question has been answered, say so. Use the accept button (the one with the checkmark) next to the answer which best solves your problem. \$\endgroup\$ Aug 15, 2012 at 15:47

2 Answers 2

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Wrist watches probably use the 9mm ones, or even larger. You won't find them smaller, because they would hardly produce sound anymore. The actual piezo-electric ceramic is mounted on a diaphragm which flexes up and down as the piezo stretches or shrinks under voltage excitement. The piezo needs to have a certain size for this, otherwise there would be hardly any flexing, and no sound.

enter image description here

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  • \$\begingroup\$ This could be a terminology thing. I've not got a good internet connection so can't search that much, but I tend to find plastic encased piezo elements are called "piezo buzzers" and the small metal bare discs are called "piezo elements". A 9mm element is thin and small, a 9mm buzzer could be up to 5mm thick, increasing bulk. See what the OP says? \$\endgroup\$ May 30, 2012 at 6:23
  • \$\begingroup\$ @Cybergibbons - I think I know what you mean. But the piezo buzzers have a piezo element inside, and the same applies. Also for active buzzers, by the way (that really high ones). \$\endgroup\$
    – stevenvh
    May 30, 2012 at 6:29
  • \$\begingroup\$ Yes - they are all the same active element, but just different in size when the casing is included. So it could be that the OP hasn't considered the bare elements. \$\endgroup\$ May 30, 2012 at 6:31
  • \$\begingroup\$ @Cybergibbons - I think he means the bare elements. A 9mm housing would mean a 6 to 7mm diaphragm maximum, and I've never seen anything that small. In my experience there's nothing below 9mm. \$\endgroup\$
    – stevenvh
    May 30, 2012 at 6:34
  • \$\begingroup\$ This is 9mm and is encased: farnell.com/datasheets/97539.pdf \$\endgroup\$ May 30, 2012 at 6:38
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If 9mm piezo elements are too large, you're basically stuck with a magnetic sounder. If those are still not small enough, well, the cell phone and earbud industries have spent millions trying to make really small speakers and this is the best they've done. You need to try something different.

If the magnetic sounder requires too much power, you will simply need to provide it with less power. For every part that I've worked with (just one) and every datasheet I looked up (three), the required currents were for operation at rated voltages. I have a Star Micronics NFT-03A electromagnetic sounder on my EK-LM3S6965 board. That part has the same form factor (visually) as their other NFT parts, it's tiny at about 5mm by 5mm by 2mm, but there's no datasheet and it's not available through the ordinary distributors. Other parts like this CUI buzzer are available in similar packages. They usually require between 70 and 110 mA, but consider the sound pressure levels that they generate and the drive method. The CUI datasheet says:

current consumption | at rated voltage, 4,000 Hz square wave, ½ duty | 110 mA

Clearly, this will be less if you drive it at a lower voltage, it will likely be less if you drive it at a lower frequency, and it will be less if you drive it at a lower duty cycle. You said 'buzzer', so you are probably able to tolerate the different sound produced by driving it with a 1000 Hz rectangular wave at 10% duty cycle. If it can be quieter, then drive it at lower voltage (or apply an ultrasonic PWM to the driver).

As an alternative, consider beeping the sounder intermitently rather than providing a continuous tone. Even at 1 Hz beeps, the thermal overload protection in your power supply shouldn't kick in during brief applications of power. Remember, the easiest way to lower power consumption is to turn the thing off.

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