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The ZMCT103C 5A AC Current Transformer Sensor Module is a compact, high-precision non-invasive current sensing board designed to measure single-phase AC load currents up to 5A RMS. The module uses the ZMCT103C micro current transformer, which isolates the low-voltage control circuit from high-voltage AC mains power.

Equipped with an onboard precision operational amplifier and an adjustable gain potentiometer, the module amplifies the low-level secondary AC voltage output generated by the transformer. This allows microcontrollers with integrated Analog-to-Digital Converters (ADCs)—such as Arduino, ESP32, or STM32—to read precise peak-to-peak voltage representations of the passing AC load current. It is an ideal component for building smart energy meters, power monitor plugs, overcurrent protective switches, and appliance health monitoring systems.

Key Features and Benefits

• High-Precision Micro Current Transformer: Employs the ZMCT103C core transformer featuring high linearity, high isolation voltage, and minimal phase error.

• Galvanic Isolation: Physical separation between the primary AC line and the microcontroller circuit guarantees user and component safety.

• Onboard Signal Amplifier: Includes an active op-amp conditioning circuit with an adjustable potentiometer to fine-tune signal amplification gain.

• Direct Microcontroller Interface: Outputs an analog sine wave voltage centered around half VCC​ suitable for direct reading via microcontroller ADC pins.

• Compact & Easy to Mount: Small footprint with standard 0.1" ($2.54\text{mm}$) header pins for easy breadboard and PCB integration.

Technical Specifications

Pinout & Wiring Guide

4-Pin Header Interface:

• VCC: Supply Voltage Positive ($+5.0\text{V DC}$).

• GND: Power Supply Ground ($0\text{V}$).

• OUT: Analog Output Voltage Signal (Connect to Arduino ADC pin A0).

• NC / GND: Not Connected or Ground reference pin.

Primary Wire Insertion:

Pass only ONE line wire (Live/Phase or Neutral, but NOT both together) of the AC load through the central hole of the ZMCT103C transformer.

SAFETY WARNING: High Voltage Mains Risk. Always ensure AC power is turned off before threading wires through the sensor hole. Do not thread both Live and Neutral through the hole simultaneously, as their currents will cancel each other out, resulting in a zero reading.

Arduino Quick-Start Code Example

This snippet calculates the Peak-to-Peak voltage and computes the estimated RMS AC current:

const int SENSOR_PIN = A0; // Connect Module OUT pin to Arduino A0

void setup() {
  Serial.begin(9600);
  Serial.println("ZMCT103C AC Current Sensor Test Initialized.");
}

void loop() {
  float voltagePeakToPeak = getPeakToPeakVoltage(SENSOR_PIN);
  
  // Calculate RMS voltage from Peak-to-Peak
  float voltageRMS = (voltagePeakToPeak / 2.0) * 0.707;

  // Calibration factor (adjust based on potentiometer setting)
  // Example: 1V RMS ~ 1A AC RMS
  float currentRMS = voltageRMS * 1.0; 

  Serial.print("Peak-to-Peak Voltage: ");
  Serial.print(voltagePeakToPeak);
  Serial.print(" V | RMS Current: ");
  Serial.print(currentRMS);
  Serial.println(" A");

  delay(1000);
}

float getPeakToPeakVoltage(int pin) {
  int minVal = 1023;
  int maxVal = 0;
  
  unsigned long startMillis = millis();
  while (millis() - startMillis < 100) { // Read for 100ms (5 full AC cycles at 50Hz)
    int readValue = analogRead(pin);
    if (readValue > maxVal) maxVal = readValue;
    if (readValue < minVal) minVal = readValue;
  }

  float peakToPeak = ((maxVal - minVal) * 5.0) / 1023.0;
  return peakToPeak;
}

Applications

• AC Appliance Energy Monitors: Smart plugs and power monitoring sockets to measure power consumption of home devices.

• Overcurrent Protection Circuits: Automatic safety cut-off circuits for motors, pumps, and air conditioners.

• Smart Grid & Home Automation: IoT-based current monitoring hubs powered by ESP32 or ESP8266.

• Load Diagnostics: Detecting machine operation states (ON, OFF, Idle, or Stalled) based on current draw.

Package Includes

• 1 x ZMCT103C 5A Range Single-Phase AC Current Transformer Sensor Module

Shipping & Delivery

• Free shipping on orders above ₹999 across India

• Dispatched within 1-3 business days

• Expected delivery: 3-7 business days depending on location

• Secure packaging to ensure safe transit of electronic components