Pond Water Level Monitor for Aquaculture

1. Introduction

In aquaculture (shrimp, fish farming), pond/tank water level directly affects animal health — too little water causes heat stress and low dissolved oxygen, while overflow causes water loss and pollutes the surrounding area. This project mounts an HC-SR04 ultrasonic sensor above the pond to measure the distance down to the water surface in real time, converts it to a water-level percentage, and sounds a local buzzer alert when the level drops too low (needs a top-up) or rises too high (risk of overflow/flooding).

This is a non-contact measurement approach well suited to pond environments, since the sensor never touches the water — reducing the risk of corrosion or fouling compared to float-type or electrode-based water-level sensors.

2. Components Needed

3. Wiring Diagram

Important hardware safety note:

• The HC-SR04 outputs its ECHO pulse at 5V, but the ESP32's GPIO only tolerates up to about 3.3V (~3.6V absolute maximum). When deploying on real hardware,

• you must use a resistor voltage divider (e.g. 1kΩ in series to GND through a 2kΩ, tapping the midpoint into GPIO27) or a level-shifter module on the ECHO line before connecting it to the ESP32 — otherwise you risk damaging the GPIO pin/chip over time.

• The sensor also needs to be mounted in a watertight enclosure when placed outdoors or over the pond, to prevent damage from rain/humidity.

4. Example #1 — Basic Distance Measurement with the HC-SR04

#define TRIG_PIN 26
#define ECHO_PIN 27

void setup() {
  Serial.begin(115200);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
}

void loop() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  long duration = pulseIn(ECHO_PIN, HIGH, 25000);
  float distanceCm = duration * 0.0343 / 2.0;

  if (duration == 0) {
    Serial.println("Khong doc duoc cam bien (timeout)");
  } else {
    Serial.print("Khoang cach: ");
    Serial.print(distanceCm);
    Serial.println(" cm");
  }

  delay(1000);
}

5. Example #2 — Buzzer Alert When Water Level Crosses a Threshold

#define BUZZER_PIN 25

const float DISTANCE_LOW_WATER_CM = 130.0;  // qua xa cam bien = nuoc thap

void setup() {
  pinMode(BUZZER_PIN, OUTPUT);
  digitalWrite(BUZZER_PIN, LOW);
}

void loop() {
  float distanceCm = 140.0; // thay bang gia tri do tu HC-SR04 thuc te

  if (distanceCm > DISTANCE_LOW_WATER_CM) {
    digitalWrite(BUZZER_PIN, HIGH); // canh bao nuoc thap
  } else {
    digitalWrite(BUZZER_PIN, LOW);
  }

  delay(1000);
}

6. Example #3 — The Complete Pond Water-Level Monitoring Application

/*
  Theo doi muc nuoc ao nuoi thuy san
  Board: ESP32 DevKit V1 (30 pins)
  Cam bien: HC-SR04 (sieu am do khoang cach tu mep ao xuong mat nuoc)
  Canh bao tai cho: Active Buzzer

  Wiring (khop voi diagram tren IoTLabs Maker):
    HC-SR04   TRIG -> GPIO26     ECHO -> GPIO27
              VCC  -> VIN(5V)    GND  -> GND
    Buzzer    IO   -> GPIO25     VCC  -> 3V3   GND -> GND

  LUU Y QUAN TRONG (an toan phan cung):
    HC-SR04 xuat xung ECHO muc 5V nhung GPIO ESP32 chi chiu duoc toi da 3.3V (~3.6V).
    Trien khai thuc te BAT BUOC dung cau phan ap tro (vi du 1kOhm + 2kOhm) tren chan ECHO
    truoc khi noi vao GPIO27, neu khong se co nguy co hong chan GPIO/chip ve lau dai.
    Ngoai ra can op ky watertight cho dau do khi lap ngoai troi/tren mat ao.

  Nguyen ly do muc nuoc:
    distance_cm = khoang cach tu cam bien (gan mieng ao) xuong mat nuoc.
    muc nuoc CAO  <-> distance_cm NHO (nuoc gan cam bien)
    muc nuoc THAP <-> distance_cm LON (nuoc xa cam bien)
  Canh bao khi muc nuoc qua thap (can bom bo sung) hoac qua cao (nguy co tran/ngap).
*/

#define TRIG_PIN 26
#define ECHO_PIN 27
#define BUZZER_PIN 25

// Hieu chinh theo kich thuoc ao thuc te (khoang cach tu cam bien den day/mep ao)
const float SENSOR_TO_EMPTY_CM = 150.0; // khoang cach khi ao can (muc nuoc = 0%)
const float SENSOR_TO_FULL_CM  = 20.0;  // khoang cach khi ao day (muc nuoc = 100%)

const float LOW_LEVEL_ALERT_PCT  = 20.0;  // canh bao muc nuoc thap
const float HIGH_LEVEL_ALERT_PCT = 95.0;  // canh bao muc nuoc qua cao / sap tran

const unsigned long MEASURE_INTERVAL_MS = 3000;
const unsigned long PULSE_TIMEOUT_US = 25000; // ~4.3m, du cho khoang cach thuc te trong ao

unsigned long lastMeasure = 0;
bool sensorTimeoutSeen = false;

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

  unsigned long duration = pulseIn(ECHO_PIN, HIGH, PULSE_TIMEOUT_US);
  if (duration == 0) {
    return -1.0; // timeout / khong doc duoc - cam bien mat ket noi hoac ngoai tam
  }
  return duration * 0.0343 / 2.0; // toc do am thanh ~343 m/s
}

void setBuzzer(bool on) {
  digitalWrite(BUZZER_PIN, on ? HIGH : LOW);
}

void setup() {
  Serial.begin(115200);
  delay(300);
  Serial.println();
  Serial.println(F("=== Theo doi muc nuoc ao nuoi IoTLabs - Boot OK ==="));

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(BUZZER_PIN, OUTPUT);
  digitalWrite(TRIG_PIN, LOW);
  setBuzzer(false);

  Serial.println(F("HC-SR04 + Buzzer san sang. Bat dau do muc nuoc dinh ky."));
}

void loop() {
  unsigned long now = millis();
  if (now - lastMeasure < MEASURE_INTERVAL_MS) {
    return;
  }
  lastMeasure = now;

  float distanceCm = measureDistanceCm();

  if (distanceCm < 0) {
    sensorTimeoutSeen = true;
    setBuzzer(false); // khong doan canh bao khi khong co du lieu tin cay
    Serial.println(F("{\"distance_cm\":null,\"level_pct\":null,\"alert\":null,\"status\":\"sensor_timeout\"}"));
    return;
  }
  sensorTimeoutSeen = false;

  // Quy doi khoang cach -> % muc nuoc, gioi han 0-100
  float levelPct = (SENSOR_TO_EMPTY_CM - distanceCm) /
                    (SENSOR_TO_EMPTY_CM - SENSOR_TO_FULL_CM) * 100.0;
  if (levelPct < 0) levelPct = 0;
  if (levelPct > 100) levelPct = 100;

  const char* alert = "normal";
  bool buzzerOn = false;
  if (levelPct <= LOW_LEVEL_ALERT_PCT) {
    alert = "low_water";
    buzzerOn = true;
  } else if (levelPct >= HIGH_LEVEL_ALERT_PCT) {
    alert = "high_water";
    buzzerOn = true;
  }
  setBuzzer(buzzerOn);

  Serial.print(F("{\"distance_cm\":"));
  Serial.print(distanceCm, 1);
  Serial.print(F(",\"level_pct\":"));
  Serial.print(levelPct, 1);
  Serial.print(F(",\"alert\":\""));
  Serial.print(alert);
  Serial.println(F("\",\"status\":\"ok\"}"));
}

7. Common Issues

8. Summary

This pond water-level monitoring system catches a too-low or too-high water level early, without a sensor that touches the water directly — well suited to the harsh conditions of an aquaculture pond.

The local buzzer alert lets operators know right away, even with no network connection.

Possible extensions: send water-level data over MQTT to a dashboard monitoring multiple ponds at once, or integrate automatic pump control via a relay when the level drops below a safe threshold.