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I am planning on using the following buzzer in my design ( SMACT-25-P15): https://uk.rs-online.com/web/p/piezo-buzzer-components/8055272/

It says it requires external circuitry for operation. I have added the following here: enter image description here

24V_IN_BUCK goes to the positive terminal and BUZZER1_N goes to the negative. The gate of the FET is controlled by the MCU.

It's a 100dB continuous buzzer. I am unsure how this needs to be driven however. To get a 100dB continuous sound output, does it need to be switched at a specific frequency? Will this circuit do the trick?

Extra note: Ideally i would use this buzzer: https://uk.rs-online.com/web/p/piezo-buzzer-components/1446628/ (PKMCS1818E20A0-R1). Its got more readily available stock and i am not limited to RS. It however requires 18V max DC. My circuit has 5V and 24V and i don't want to add an additional buck in there. Is there a way i could drive this? Say by constantly pulsing it as it also requires external drive

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  • \$\begingroup\$ Be careful, because there's a 2KHz maximum frequency limit on your second buzzer (from RS) which you linked in your question. One of the answers is suggesting 3-4 KHz, but that exceeds the maximum specified. (Why is there a max freq specified? Hmmmm.) \$\endgroup\$ Oct 28, 2021 at 15:07
  • \$\begingroup\$ The T in your part number means "Transducer" meaning passive AC type , not DC. Did you intend that or just choose it for another reason without telling us, like lower cost. \$\endgroup\$ Oct 28, 2021 at 17:15
  • \$\begingroup\$ YOUR IDEAL PART PKMCS1818E20A0-R1 is surface mount. Do you know how to solder this? If at 10 mA * 1k = 10V drop you get 14V \$\endgroup\$ Oct 28, 2021 at 17:38

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The SMACT-25-P15 buzzer is only a transducer (no integrated electronics) and requires a square wave signal between 3kHz and 4kHz to produce the maximum sound pressure, 3.35kHz is recommended. The 24VDC you are driving is well within the 0 to 30VDC operating voltage range. So use a PWM mode output pin from your microcontroller to drive this device. Your proposed circuit should work fine. I assume your microcontroller output pin voltage is at least 3.3V to operate (turn on) the MOSFET.

Don't forget to peel off the protective tab after you have soldered it to the PCB for the highest sound output.

If you want to use the PKMCS1818E20A0-R1 part instead, this too is only a transducer and does not include integrated electronics, so you will need to provide a pulsed output from your microcontroller. Also, as you stated, you will need to deal with the lower (18VDC) operating voltage. You can get by on using a simple adjustable LDO linear regulator that requires only three parts (regulator chip plus two resistors), or a fixed LDO like the BA17818FP-E2 that outputs at 18VDC.

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  • \$\begingroup\$ Be aware that the sound output is quite sensitive to the frequency- if you really need the 100dB then you’ll need to get as close to 3.35kHz as you can; if you can live with a few dB less than it’s not so critical. Also the single -ended circuit you’ve shown will be somewhat inefficient, if this is a concern then perhaps consider using a slightly more complex push-pull driver \$\endgroup\$
    – Frog
    Oct 28, 2021 at 19:21
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    \$\begingroup\$ Frog - Good point. As that "maximum sound pressure vs. frequency" chart in the SMACT-25-P15 datasheet suggest, the output will decrease significantly as you get out of the 3kHz to 4kHz range. If the maximum sound output is important, then you may want to play with the frequency within that range to discover the best value. Also, it is important that you keep the PWM at 50% duty cycle for maximum sound output. \$\endgroup\$ Oct 28, 2021 at 19:56
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Your link shows The T version but with a link to a common datasheet with all the part numbers.

The T in your part number and link means "Transducer" meaning PASSIVE AC type , not DC.

If you prefer the DC type choose the one which is loud enough or you or has the features you want and don't assume we know what you want.

enter image description here

The suffix in the part number matters. Read again. The T version with AC means you can vary the frequency with a simple circuit but not quite as simple as you show, which is suitable for a lower current , quieter sound in the 80 dB range.

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  • \$\begingroup\$ Tony - Again I have added the required reference link for an image in your answer. Please remember that it is your responsibility to do this, when including information from elsewhere in an answer. Thanks. \$\endgroup\$
    – SamGibson
    Oct 28, 2021 at 17:47

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