1. Piezo Speaker Driver Circuit
2. High Frequency Piezo Driver Circuit
3. Piezo Pump Driver Circuit
4. Piezo Oscillator Driver Circuit
5. Piezo Actuator Driver Circuit

Ultrasonic transducer driver circuit. Ultrasonic transducer driver circuit on ultrasonic cleaning workpiece, the ultrasonic generator PCB are allowing the particles attached to the workpiece, oil and other mechanical vibration with the ultrasound off or dissolved or emulsified and so on, to achieve the purpose of cleaning the workpiece. The used inductor might not be critical with its value, but the value should as high as possible, the higher the sharper the reproduction from the piezo. A simple piezo transducer driver circuit or a simple piezo alarm circuit is shown in the following circuit using a NAND gate.

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Recently, I have ordered smt-0440-t-r buzzer from Mouser.

Circuit is as shown in figure.

Microcontroller pin transmits square wave of 4kHz as mentioned in the datasheet. However, the sound isn't audible. When I am at a distance of 1-2cm from the buzzer, I am hearing very low intensity sound. Any fixes?

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4 Answers

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1. Look at your transducer. If it has a sticker over the sound hole remove it.
2. The resonant frequency is 4K +/- 500Hz. Try changing the frequency through several other settings to see if resonance is the problem.
3. Check the drive waveform from the MCU pin. Does it allow the NPN transistor to turn full on and off? Use an oscilloscope to check this.

Michael KarasMichael Karas$endgroup$$begingroup$

You have checked almost everything and nothing gave a definite improvement. I'm having a guess here that you don't have exactly the same buzzer as in the datasheet. With a specified coil resistance of 17 Ohm this should be a fixed coil / moving diaphragm buzzer, which will work OK with your original circuit.

However if you actually have a piezo buzzer you need a slightly different drive circuit to get a good sound level out of it. A piezo buzzer acts very similar to a capacitor and needs a push-pull driver circuit to charge and then discharge the capacitance of the piezo. However a piezo will work quite well with a small modification to your original circuit, with a 1k Ohm resistor placed across the piezo buzzer to discharge its capacitance.

Piezo Speaker Driver Circuit

^{simulate this circuit – Schematic created using CircuitLab}

Steve GSteve G$endgroup$$begingroup$

How is your hearing and what is your age? If you are 45 years old then your normal hearing loss at 4kHz is -23dB so you will barely hear it. Hearing aids like mine (I am 73 soon) will fix the loss.

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I've had and solved this exact problem that you're having. What Steve said is the key, a piezo buzzer appears electrically as a capacitor.

Now with that in mind, look at your circuit. You're just going to charge the capacitor once, and then it's going to more or less stay charged and produce no more sound.

The loudest way to drive this circuit is using a full H bridge, this will provide a VPP of 2x your input voltage.

Another method that will work is to use a totem pole driver, or an op-amp so that you can drive one side of the piezo high and low. This is simpler, but it will produce half the amplitude.

High Frequency Piezo Driver Circuit

What I ended up doing in my application is just driving both sides of the piezo directly using 2 microcontroller outputs. This will work fine with an appropriate current limiting resistor, and it may be loud enough for your application.

Drew

Piezo Pump Driver Circuit

Drew

Piezo Oscillator Driver Circuit

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Piezo Actuator Driver Circuit

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