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How to calculate PWM duty cycle to compensate for different piezo sounder response at different frequencies?

I have a piezo sounder, and the datasheet informs me that I will get the following response:

Frequency Response 200Hz 74dB 1000Hz 81dB

If I set my PWM duty cycle to 100% at 200Hz to get 74dB, how do I calculate the PWM duty cycle required to give the same response of 74dB at 1000Hz?

Thanks kindly for any help.

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    \$\begingroup\$ Uh. If you set your PWM to either 0% or 100% at 200 Hz you get 0 Hz. Have you used PWM before? Do you understand what a piezo does and how it works? (allaboutcircuits.com/technical-articles/… ) Do you know what a natural resonance frequency (or frequencies) is or what it might mean to operate something away from that frequency? You have some reading to do. \$\endgroup\$
    – jonk
    Jul 26, 2017 at 23:52
  • \$\begingroup\$ It's an inverting output. So 100% duty cycle is not DC. \$\endgroup\$
    – Tantalum
    Jul 27, 2017 at 0:08
  • \$\begingroup\$ Yes, I've used PWM before. It works fine on my current project. Just looking to add a few refinements. \$\endgroup\$
    – Tantalum
    Jul 27, 2017 at 0:10
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    \$\begingroup\$ Measure it with a SPL meter, and adjust accordingly. Seriously, there are going to be a ton of variables which influence a calculated answer. \$\endgroup\$
    – rdtsc
    Jul 27, 2017 at 1:19
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    \$\begingroup\$ @Tantalum: Jonk is correct. 0% PWM will result in 0 V continuous. 100% PWM will result in continuous V+ with no 0 V pulses. That is DC. If it is inverting then 100% will give you 0 V. That can be considered DC with a value of 0 A. \$\endgroup\$
    – Transistor
    Apr 29, 2018 at 16:59

2 Answers 2

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schematic

simulate this circuit – Schematic created using CircuitLab

This is a variable clock or an Astable Multivibrator or a Relaxation Oscillator. Choose any buffer to suit the voltage or power level required. CMOS has an impedance of ~300 Ohms for 74HC and ~50 Ohms for 74ALCxx ~5V

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A piezo sounder has a horrible frequency response. With a complicated linear EQ circuit I doubt you can make good sound, then it can feed a class-D (PWM) amplifier that powers the sounder. You did not post the part number or frequency response graph of your sounder, here is mine: piezo

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