15. System Intergration¶
Kindly refer to my Project page where i have shown detailed steps taken
Voltage Regulator¶
An LM7805 voltage regulator was used to convert the 12V supply to a regulated 5V output. This 5V supply was used to power the loads(control circuitry,12v pump and 12v solenoid valve). I ised 10µF capacitor connected to the regulator output to improve voltage stability and reduce fluctuations.
MOSFET Switching Circuit¶
An N-channel MOSFET was used as an electronic switch to control the 12V solenoid valve. The gate was connected to the controller output through a 47Ω resistor, while a 10kΩ pull-down resistor was connected between the gate and ground to keep the MOSFET OFF when no signal was present. The drain was connected to the valve’s negative terminal and the source to ground. When a control signal was applied, the MOSFET turned ON and allowed current to flow through the valve.
Solenoid Valve Connection¶
The positive terminal of the 12V solenoid valve was connected directly to the 12V supply. The negative terminal was connected to the MOSFET drain. This allowed the controller to switch the valve ON and OFF through the MOSFET.
Pump Connection¶
The 12V water pump was connected in parallel with the solenoid valve. The positive terminal was connected directly to the 12V supply, while the negative terminal was connected to the MOSFET drain. As a result, both the pump and valve could be controlled simultaneously using a single MOSFET.
Power Filtering¶
A 100nF capacitor was connected across the main 12V supply line to reduce electrical noise and improve the stability of the power circuit.
Programming¶
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <WiFi.h>
#include <PubSubClient.h>
// ================= LCD =================
LiquidCrystal_I2C lcd(0x27, 16, 2);
// ================= WiFi =================
const char* ssid = "MT";
const char* password = "#@Innovate";
// ================= MQTT =================
const char* mqtt_server = "broker.emqx.io";
WiFiClient espClient;
PubSubClient client(espClient);
// ================= Pins =================
const int turbidityPin = A2;
const int CONTROL_PIN = D10; // Active LOW output
const int flowPin = D2; // Flow sensor pin
// ================= Turbidity Calibration =================
float V_clean = 2.77;
float V_dirty = 0.90;
// ================= Flow Variables =================
volatile int pulseCount = 0;
float flowRate = 0.0;
float totalLiters = 0.0;
unsigned long previousMillis = 0;
// =====================================================
// Interrupt for Flow Sensor
// =====================================================
void IRAM_ATTR pulseCounter() {
pulseCount++;
}
// =====================================================
// Average Turbidity Reading
// =====================================================
int getAverage() {
int sum = 0;
for (int i = 0; i < 20; i++) {
sum += analogRead(turbidityPin);
delay(5);
}
return sum / 20;
}
// =====================================================
// WiFi Connection
// =====================================================
void setup_wifi() {
Serial.print("Connecting to WiFi");
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("\nWiFi connected");
Serial.println(WiFi.localIP());
}
// =====================================================
// MQTT Reconnection
// =====================================================
void reconnect() {
while (!client.connected()) {
Serial.print("Connecting MQTT...");
if (client.connect("ESP32WaterPurifier")) {
Serial.println("Connected");
} else {
Serial.print("Failed, rc=");
Serial.print(client.state());
Serial.println(" Retrying...");
delay(2000);
}
}
}
// =====================================================
// Setup
// =====================================================
void setup() {
Serial.begin(115200);
pinMode(CONTROL_PIN, OUTPUT);
digitalWrite(CONTROL_PIN, HIGH); // Default OFF
pinMode(flowPin, INPUT_PULLUP);
attachInterrupt(digitalPinToInterrupt(flowPin),
pulseCounter,
FALLING);
Wire.begin(D6, D7);
lcd.init();
lcd.backlight();
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("Water Purifier");
lcd.setCursor(0, 1);
lcd.print("Starting...");
delay(2000);
setup_wifi();
client.setServer(mqtt_server, 1883);
Serial.println("=== SYSTEM READY ===");
}
// =====================================================
// Loop
// =====================================================
void loop() {
if (!client.connected()) {
reconnect();
}
client.loop();
// ================= TURBIDITY =================
int raw = getAverage();
float voltage = raw * (3.3 / 4095.0);
float turbidity =
((V_clean - voltage) /
(V_clean - V_dirty)) * 100.0;
// Clamp values
if (turbidity < 0) turbidity = 0;
if (turbidity > 100) turbidity = 100;
String status;
// ================= Decision Logic =================
if (turbidity < 20) {
status = "CLEAN";
// Active LOW output OFF
digitalWrite(CONTROL_PIN, HIGH);
}
else if (turbidity < 50) {
status = "SLIGHT DIRTY";
digitalWrite(CONTROL_PIN, LOW);
}
else if (turbidity < 80) {
status = "DIRTY";
digitalWrite(CONTROL_PIN, LOW);
}
else {
status = "VERY DIRTY";
digitalWrite(CONTROL_PIN, LOW);
}
// ================= FLOW SENSOR =================
unsigned long currentMillis = millis();
if (currentMillis - previousMillis >= 1000) {
previousMillis = currentMillis;
// YF-S201 calibration factor
flowRate = pulseCount / 7.5;
float litersThisSecond = flowRate / 60.0;
totalLiters += litersThisSecond;
pulseCount = 0;
// MQTT Messages
char flowMsg[20];
char totalMsg[20];
char turbidityMsg[20];
sprintf(flowMsg, "%.2f", flowRate);
sprintf(totalMsg, "%.2f", totalLiters);
sprintf(turbidityMsg, "%.1f", turbidity);
// ================= MQTT Publish =================
client.publish("water/flow", flowMsg);
client.publish("water/total", totalMsg);
client.publish("water/turbidity", turbidityMsg);
client.publish("water/status", status.c_str());
// ================= Serial =================
Serial.print("Turbidity: ");
Serial.print(turbidity, 1);
Serial.print("% | ");
Serial.print(status);
Serial.print(" | Flow: ");
Serial.print(flowRate);
Serial.print(" L/min");
Serial.print(" | Total: ");
Serial.print(totalLiters);
Serial.println(" L");
// ================= LCD =================
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("T:");
lcd.print((int)turbidity);
lcd.print("% ");
if (turbidity < 20)
lcd.print("RUN");
else
lcd.print("STOP");
lcd.setCursor(0, 1);
lcd.print("F:");
lcd.print(flowRate, 1);
lcd.print("L/m");
}
}
I generated the above code using chatgpt using the following prompt;
Develop a single Arduino sketch for the Seeed Studio XIAO ESP32 that combines the existing turbidity monitoring system with a YF-S201 flow sensor and MQTT communication. The system should read turbidity from A2, measure flow rate and total volume using the flow sensor on D2, display turbidity status and flow information on a 16×2 I2C LCD (SDA = D6, SCL = D7), connect to Wi-Fi and publish flow rate, total liters, turbidity percentage, and water quality status to an MQTT broker every second. The valve/MOSFET connected to D10 should be controlled using active-low logic based on the turbidity level.