Piezo

A piezoelectric sensor converts mechanical stress into electrical signals using piezoelectric materials like quartz or ceramics. When pressure or vibration is applied, these materials generate a voltage proportional to the force. Widely used in applications such as accelerometers, microphones, and pressure sensors, piezoelectric sensors offer high sensitivity, fast response and durability.

Applications

• Vibration monitoring in industrial machinery to detect imbalances or bearing faults
• Impact detection in sports equipment to measure strike force
• Acoustic pickup in musical instruments (e.g., guitar pickups, violins)
• Medical devices: in ultrasound imaging transducers.
• Consumer electronics: tap detection in mobile devices or wearables.

Technical Specifications

📄 Piezo element datasheet (90 kB)

Functionality and safety precautions

A piezo sensor generates a voltage when mechanically deformed, which can be up to 30 V or more. This could easily damage the connected microcontroller, since it only tolerates 5V or 3.3V. To limit those voltage spikes a 1MΩ resistor is placed in parallel between Cathode and Anode of the piezo disc. This helps protecting the microcontroller by dissipating excess voltage. Additionally a 5V (or 3.3V) Zener diode can also be placed parallel with the resistor to prevent voltage spikes above 5V (resp.: 3.3V).
The sensitivity of the piezo sensor can be adjusted by selecting different resistor values (~1MΩ to 10MΩ). A smaller resistor decreases sensitivity.

Mount the piezo sensor mechanically to avoid false readings due to loose connections.

Prevent strong mechanical shocks that could generate excessive voltages.

Used Components

Connections

Setup & Programming

Arduino

#define PIN_PIEZO A0

void setup() {
    pinMode(PIN_PIEZO, INPUT);
    Serial.begin(9600);
}

void loop() {
    int sensorValue = analogRead(PIN_PIEZO);
    Serial.println(sensorValue);
    delay(25);
}

Arduino with Interrupts

Another way to interface a piezo sensor with an Arduino is by using an interrupt. However, this method can only detect a binary signal - that is, whether the piezo was triggered or not - but not how strongly it was pressed.

#define PIN_PIEZO 2
#define CUSTOM_DELAY 1000

#define lmillis() ((long)millis())

volatile int pressedSum = 0;
long lastAction;

void setup() {
    Serial.begin(9600);
    attachInterrupt(digitalPinToInterrupt(PIN_PIEZO), handlePiezo, RISING);
    lastAction = lmillis() + CUSTOM_DELAY;
}

void loop() {
    if (lmillis() - lastAction >= 0) {
        lastAction = lmillis() + CUSTOM_DELAY;
        Serial.println("Pressed on piezo: " + String(pressedSum) + " times");
    }
}

void handlePiezo() {
    pressedSum++;
}

ESP32

#define PIN_PIEZO 13

void setup() {
	pinMode(PIN_PIEZO, INPUT);
	Serial.begin(9600);
}

void loop() {
	int sensorValue = analogRead(PIN_PIEZO);
	Serial.println(sensorValue);
	delay(25);
}

Testing

After connecting the components and uploading the code to the microcontroller, you can gently tap the piezo disc. Upon opening the serial console or plotter, you should see that the input values change depending on the pressure you apply.