Arduino Air Compressor DIY Step-by-Step Guide

/*
  Arduino Air Compressor Controller
  Monitors pressure via an analog sensor and controls a relay.
*/

// --- Configuration ---
const int SENSOR_PIN = A0;      // Pressure sensor signal pin
const int RELAY_PIN = 7;        // Relay control pin

// Pressure Settings (Adjust these to match your system)
const int CUT_OFF_PRESSURE = 90; // PSI: Compressor OFF
const int CUT_IN_PRESSURE = 60;  // PSI: Compressor ON

// Sensor Calibration (0.5V = 0 PSI, 4.5V = Max PSI)
const float MAX_SENSOR_PSI = 100.0;
const float MIN_SENSOR_VOLTAGE = 0.5;
const float MAX_SENSOR_VOLTAGE = 4.5;

void setup() {
  Serial.begin(9600);           // For debugging
  pinMode(RELAY_PIN, OUTPUT);   // Relay control
  pinMode(SENSOR_PIN, INPUT);   // Pressure sensor input

  digitalWrite(RELAY_PIN, LOW); // Start with compressor OFF
  Serial.println("System Initialized...");
}

void loop() {
  // 1. Read sensor
  int rawADC = analogRead(SENSOR_PIN);

  // 2. Convert ADC (0-1023) to Voltage (0-5V)
  float voltage = rawADC * (5.0 / 1023.0);

  // 3. Convert Voltage to Pressure (PSI)
  float pressure = 0.0;
  if (voltage >= MIN_SENSOR_VOLTAGE) {
    pressure = ((voltage - MIN_SENSOR_VOLTAGE) * MAX_SENSOR_PSI) / 
               (MAX_SENSOR_VOLTAGE - MIN_SENSOR_VOLTAGE);
  }

  // 4. Debugging output
  Serial.print("Voltage: "); Serial.print(voltage);
  Serial.print("V | Pressure: "); Serial.print(pressure); Serial.println(" PSI");

  // 5. Control logic (with hysteresis)
  if (pressure < CUT_IN_PRESSURE) { digitalWrite(RELAY_PIN, HIGH); // Turn compressor ON Serial.println("Status: COMPRESSOR ON"); } else if (pressure >= CUT_OFF_PRESSURE) {
    digitalWrite(RELAY_PIN, LOW);   // Turn compressor OFF
    Serial.println("Status: COMPRESSOR OFF");
  }

  delay(500); // Prevents noise and rapid cycling
}