Introduction

The ACS712 is a hall-effect based current sensor that can measure both AC and DC currents up to ±5A. It provides analog output proportional to the measured current, making it ideal for energy monitoring, motor control, and over-current protection applications.

Key Features

Technical Specifications

Pin Configuration

Wiring Diagram

// Basic Connections:
// VCC → 5V
// GND → GND
// OUT → A0
// IP+ → Load positive
// IP- → Load negative

Basic Current Measurement

const int sensorPin = A0;
const float mVperAmp = 185.0; // Sensitivity for 5A model
const float vRef = 5.0; // Arduino reference voltage
const int adcResolution = 1023; // 10-bit ADC

void setup() {
  Serial.begin(9600);
}

void loop() {
  float voltage = (analogRead(sensorPin) * vRef) / adcResolution;
  float zeroVoltage = vRef / 2; // 2.5V at no current
  float current = (voltage - zeroVoltage) * 1000 / mVperAmp;
  
  Serial.print("Voltage: ");
  Serial.print(voltage, 3);
  Serial.print("V\tCurrent: ");
  Serial.print(current, 2);
  Serial.println("A");
  
  delay(1000);
}

AC Current Measurement

const int samples = 200;
float offset = 2.5; // Zero current voltage (VCC/2)

void setup() {
  Serial.begin(9600);
  // Calibrate zero offset
  float sum = 0;
  for(int i=0; i<samples; i++) {
    sum += analogRead(A0);
    delay(1);
  }
  offset = (sum / samples) * (5.0 / 1023.0);
}

void loop() {
  float maxI = 0, minI = 0;
  
  for(int i=0; i<samples; i++) { float voltage = (analogRead(A0) * 5.0) / 1023.0; float current = (voltage - offset) * 1000 / 185.0; if(current > maxI) maxI = current;
    if(current < minI) minI = current;
    delay(1);
  }
  
  float peakToPeak = maxI - minI;
  float rmsCurrent = peakToPeak / (2 * sqrt(2));
  
  Serial.print("RMS Current: ");
  Serial.print(rmsCurrent, 2);
  Serial.println("A");
}

Advanced Features

void checkOverCurrent() {
  float current = getCurrent();
  if(current > 4.0) { // 4A threshold
    digitalWrite(13, HIGH); // Alert LED
    Serial.println("OVER CURRENT!");
  } else {
    digitalWrite(13, LOW);
  }
}

float calculatePower(float voltageSupply) {
  float current = getCurrent();
  return voltageSupply * current;
}

#define FILTER_SIZE 10
float filterBuffer[FILTER_SIZE];
int filterIndex = 0;

float filteredCurrent(float rawCurrent) {
  filterBuffer[filterIndex] = rawCurrent;
  filterIndex = (filterIndex + 1) % FILTER_SIZE;
  
  float sum = 0;
  for(int i=0; i<FILTER_SIZE; i++) {
    sum += filterBuffer[i];
  }
  return sum / FILTER_SIZE;
}

Troubleshooting