Interface Current Transformers with Arduino Microcontroller for Accurate AC Current Measurement

Current transformers (CTs) are versatile devices primarily used for monitoring and measuring AC current. They play a crucial role in a wide range of applications, from industrial settings to smart homes. Integrating CTs with an Arduino microcontroller allows for precise and flexible data collection, making it a valuable technique for both hobbyists and professionals. In this article, we will explore the methods and steps needed to interface a current transformer with an Arduino microcontroller, enabling accurate AC current measurement.

Understanding Current Transformers

A current transformer (CT) is a device that outputs a small AC voltage proportional to the current flowing through its primary winding. This output voltage is much smaller than the current, typically ranging from millivolts to volts. The key parameter that determines the output voltage is the CT's ratio and the current being measured.

Components Needed

To interface a current transformer with an Arduino microcontroller, you will need the following components:

Current Transformer (CT): Choose a CT suitable for your application, such as a 5A/1A or 100A/5A model. These models have different input and output ranges. Burden Resistor: This resistor is connected across the CT output to convert the current output to a voltage. The value of the resistor depends on the CT specifications and the expected current. Arduino Board: Any Arduino model, such as the Arduino Uno or Mega, can be used. Additional Components: For signal conditioning, you may want to consider diodes, capacitors, and resistors, although these are optional but recommended for better performance.

Wiring

The wiring process is straightforward:

Connect the CT's secondary terminals to the burden resistor. Connect the burden resistor's output to the Arduino's analog input pin. Ensure proper grounding and consider using a diode for protection against reverse voltage.

To achieve accurate readings and avoid potential damage, it's essential to ensure that the CT is rated for the current levels you are measuring. High currents can be hazardous, so always follow safety guidelines.

Arduino Code

To read and convert the voltage into current using an Arduino, you need to write and upload the appropriate code to your Arduino board. Here's an example of how to do this:

const int analogPin  A0;  // Pin where the burden resistor is connectedconst float burdenResistance  10.0;  // Burden resistor value in ohmsconst float ctRatio  100.0;  // CT ratio, e.g., 100:5  100void setup() {    (9600);  // Initialize serial communication for debugging}void loop() {    int sensorValue  analogRead(analogPin);  // Read the voltage across the burden resistor    float voltage  sensorValue / 1023.0 * 5.0;  // Scale the reading to 5V reference    float current  voltage / burdenResistance * ctRatio;  // Convert to current    (current);  // Print the current value    delay(1000);  // Delay for readability}

The code initializes serial communication in the `setup()` function. Then, within the `loop()` function, it reads the voltage value from the burden resistor, converts it to current using the known CT ratio and burden resistor value, and prints the result to the serial monitor.

Considerations

When interfacing a current transformer with an Arduino, there are several important factors to consider:

Safety: Ensure that the CT is rated for the current levels being measured. Handling high currents safely is crucial to avoid potential hazards. Calibration: Calibrate your setup to ensure accurate readings. This involves verifying the CT's output against a known current source. Filtering: If you are measuring AC current, consider implementing a low-pass filter to smooth out the readings and reduce noise.