How to Use Current Sensor ACS712 : Examples, Pinouts, and Specs

The ACS712 is a Hall effect-based current sensor that provides an analog output proportional to the current flowing through it. It is capable of measuring both AC and DC currents, making it a versatile component for a wide range of applications. The sensor is available in different variants to measure currents up to ±5A, ±20A, or ±30A. Its compact design and ease of use make it a popular choice for current monitoring and control in electrical systems.

• Power monitoring in household and industrial devices
• Overcurrent protection in circuits
• Battery management systems
• Motor control and monitoring
• Energy metering and load detection

Below are the key technical details of the ACS712 current sensor:

The ACS712 has 8 pins, but only a few are typically used in most applications. Below is the pinout:

1. Power the Sensor: Connect the Vcc pin to a 5V power supply and the GND pin to the ground of your circuit.
2. Connect the Load: Pass the current-carrying wire through the IP+ and IP- terminals. Ensure the current flows in the correct direction as indicated on the sensor.
3. Read the Output: The OUT pin provides an analog voltage proportional to the current. At 0A, the output voltage is approximately Vcc/2 (2.5V for a 5V supply). The voltage increases or decreases based on the current direction.

• Calibration: The sensor's output may vary slightly due to manufacturing tolerances. Calibrate the sensor in your application for accurate readings.
• Noise Filtering: Add a capacitor (e.g., 0.1 µF) between the OUT pin and GND to reduce noise in the output signal.
• Current Range: Ensure you select the correct ACS712 variant (±5A, ±20A, or ±30A) based on your application's current range.
• Isolation: The ACS712 provides electrical isolation between the current-carrying conductor and the sensor's output, enhancing safety.

Below is an example of how to interface the ACS712 with an Arduino UNO to measure current:

// Include necessary libraries (if any)

// Define the analog pin connected to the ACS712 OUT pin
const int sensorPin = A0;

// Define the sensitivity of the ACS712 (e.g., 185mV/A for ±5A model)
const float sensitivity = 0.185; // Sensitivity in V/A

// Define the supply voltage (Vcc) of the sensor
const float Vcc = 5.0; // Supply voltage in volts

// Define the zero-current voltage (Vcc/2)
const float zeroCurrentVoltage = Vcc / 2;

void setup() {
  Serial.begin(9600); // Initialize serial communication
}

void loop() {
  // Read the analog value from the sensor
  int sensorValue = analogRead(sensorPin);

  // Convert the analog value to voltage
  float sensorVoltage = (sensorValue / 1023.0) * Vcc;

  // Calculate the current in amperes
  float current = (sensorVoltage - zeroCurrentVoltage) / sensitivity;

  // Print the current value to the Serial Monitor
  Serial.print("Current: ");
  Serial.print(current);
  Serial.println(" A");

  delay(1000); // Wait for 1 second before the next reading
}

• Replace sensitivity with the appropriate value for your ACS712 variant (e.g., 0.1 for ±20A, 0.066 for ±30A).
• Ensure the current-carrying wire is properly connected to the IP+ and IP- terminals.

1. No Output or Incorrect Readings

   • Cause: Incorrect wiring or loose connections.
   • Solution: Double-check all connections, especially the Vcc, GND, and OUT pins.

2. High Noise in Output

   • Cause: Electrical noise or lack of filtering.
   • Solution: Add a 0.1 µF capacitor between the OUT pin and GND to filter noise.

3. Output Voltage Does Not Change

   • Cause: Current is not flowing through the IP+ and IP- terminals.
   • Solution: Ensure the current-carrying wire is properly connected and the load is active.

4. Inaccurate Current Measurements

   • Cause: Sensor not calibrated or incorrect sensitivity value used.
   • Solution: Calibrate the sensor by measuring a known current and adjusting calculations accordingly.

Q: Can the ACS712 measure both AC and DC currents?
A: Yes, the ACS712 can measure both AC and DC currents. The output voltage will vary proportionally with the instantaneous current.

Q: How do I select the correct ACS712 variant?
A: Choose the variant based on the maximum current you need to measure. For example, use the ±5A model for small currents and the ±30A model for larger currents.

Q: Is the ACS712 safe to use with high voltages?
A: Yes, the ACS712 provides electrical isolation between the current-carrying conductor and the sensor's output, making it safe for high-voltage applications.

Q: Can I use the ACS712 with a 3.3V microcontroller?
A: While the ACS712 is designed for a 5V supply, it may work with a 3.3V microcontroller if the output voltage range is within the ADC input range. However, accuracy may be affected.