Tsunami Warning Detector

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1. 01

   Place and power the ESP32

   Place the ESP32 across the breadboard center gap. Use the ESP32 3V3 pin for the 3.3 V rail and GND for the ground rail. Use the ESP32 5V/VIN pin only for the HC-SR04 5 V supply rail. Power the finished project from the ESP32 USB connector.

   • Tip: Keep all ground rails connected together.
   • Tip: Do not connect the 5 V rail to any ESP32 GPIO.

   • ⚠ Disconnect USB power before moving wires.
2. 02

   Wire the SW-420 vibration detector

   Connect SW-420 VCC to the 3.3 V rail, GND to ground, and DO to ESP32 GPIO32. Turn the module trimmer gently to set the desired vibration sensitivity.

   • Tip: The yellow LED turns on when the module’s digital output is LOW, which is the common SW-420 active state.

   • ⚠ Power the SW-420 from 3.3 V, not 5 V, so its DO signal stays safe for the 3.3 V ESP32 input.
3. 03

   Add the yellow vibration LED

   Connect ESP32 GPIO25 to one end of the 220 Ω resistor. Connect the other resistor end to the yellow LED long lead (anode). Connect the LED short lead (cathode/flat-side lead) to ground.

   • Tip: The resistor may be placed on either side of the LED, but it must remain in series with it.

   • ⚠ Never connect an LED directly from a GPIO to ground without its series resistor.
4. 04

   Wire the ultrasonic water-level sensor safely

   Mount the HC-SR04 above the water surface with its transducers facing down. Connect VCC to 5 V, GND to common ground, and TRIG to GPIO27. For ECHO, connect HC-SR04 ECHO to the 1 kΩ resistor, connect the resistor’s other end to GPIO33, then connect the 2 kΩ resistor from that same GPIO33 divider junction to ground.

   • Tip: The 1 kΩ and 2 kΩ resistors make a divider that reduces the HC-SR04’s 5 V ECHO pulse to about 3.3 V.
   • Tip: Keep the sensor dry and positioned so it has a clear view of the water surface.

   • ⚠ Never wire the HC-SR04 ECHO pin directly to GPIO33: it outputs 5 V and can damage the ESP32.
   • ⚠ The ordinary HC-SR04 board is not waterproof; keep electronics away from splash and condensation.
5. 05

   Connect the audible alarm

   Connect buzzer SIGNAL/+ to GPIO26 and buzzer GND/− to the common ground rail.

   • Tip: If your buzzer is marked + and −, GPIO26 goes to + and ground goes to −.

   • ⚠ Use a small piezo or low-current buzzer. A larger high-current buzzer needs a transistor driver, which is not part of this build.
6. 06

   Check before powering

   Check that every module shares ground, the HC-SR04 alone is powered from 5 V, the SW-420 is powered from 3.3 V, and the HC-SR04 ECHO divider is installed. After deploying, let the sensor take its initial distance reading with normal water level present.

   • Tip: A rising water level makes the measured distance decrease; a falling level makes it increase. Either direction triggers when the change between readings reaches 3 cm.

   • ⚠ This prototype is an educational local alarm, not a certified tsunami-warning instrument. Do not rely on it for public safety decisions.

#include <Arduino.h>


// Forward declarations
float measureDistanceCm();
void startAlarm();
void stopAlarm();

constexpr int VIBRATION_PIN = 32;
constexpr int TRIG_PIN = 27;
constexpr int ECHO_PIN = 33;
constexpr int YELLOW_LED_PIN = 25;
constexpr int BUZZER_PIN = 26;

constexpr float CHANGE_THRESHOLD_CM = 3.0f;
constexpr unsigned long SAMPLE_INTERVAL_MS = 250;
constexpr unsigned long ALARM_DURATION_MS = 10000;
constexpr unsigned long ECHO_TIMEOUT_US = 30000;

float baselineDistanceCm = NAN;
unsigned long lastSampleMs = 0;
unsigned long alarmStartedMs = 0;
bool alarmActive = false;

float measureDistanceCm() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  const unsigned long durationUs = pulseIn(ECHO_PIN, HIGH, ECHO_TIMEOUT_US);
  if (durationUs == 0) {
    return NAN;
  }
  return (durationUs * 0.0343f) / 2.0f;
}

void startAlarm() {
  if (!alarmActive) {
    alarmActive = true;
    alarmStartedMs = millis();
    ledcWriteTone(BUZZER_PIN, 2200);
  }
}

void stopAlarm() {
  ledcWriteTone(BUZZER_PIN, 0);
  alarmActive = false;
}

void setup() {
  Serial.begin(115200);

  pinMode(VIBRATION_PIN, INPUT);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(YELLOW_LED_PIN, OUTPUT);
  digitalWrite(YELLOW_LED_PIN, LOW);

  ledcAttach(BUZZER_PIN, 2200, 8);
  stopAlarm();

  delay(500);
  baselineDistanceCm = measureDistanceCm();
  Serial.println("Tsunami detector started.");
  if (isnan(baselineDistanceCm)) {
    Serial.println("Waiting for a valid ultrasonic reading...");
  } else {
    Serial.printf("Initial water distance: %.1f cm\n", baselineDistanceCm);
  }
}

void loop() {
  // SW-420 modules commonly assert LOW when vibration is detected.
  const bool vibrationDetected = digitalRead(VIBRATION_PIN) == LOW;
  digitalWrite(YELLOW_LED_PIN, vibrationDetected ? HIGH : LOW);

  const unsigned long now = millis();
  if (now - lastSampleMs >= SAMPLE_INTERVAL_MS) {
    lastSampleMs = now;
    const float distanceCm = measureDistanceCm();

    if (!isnan(distanceCm)) {
      if (isnan(baselineDistanceCm)) {
        baselineDistanceCm = distanceCm;
        Serial.printf("Water baseline set: %.1f cm\n", baselineDistanceCm);
      } else {
        const float changeCm = fabsf(distanceCm - baselineDistanceCm);
        Serial.printf("Distance: %.1f cm, change: %.1f cm\n", distanceCm, changeCm);

        if (changeCm >= CHANGE_THRESHOLD_CM) {
          startAlarm();
        } else {
          // A stable water level ends the alarm immediately.
          stopAlarm();
        }
        baselineDistanceCm = distanceCm;
      }
    }
  }

  // Continue an active alarm for up to ten seconds if level changes persist.
  if (alarmActive && (now - alarmStartedMs >= ALARM_DURATION_MS)) {
    stopAlarm();
  }
}

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