⚙️ What Is the ZMCT103C 5A Current Sensor (HW670)?
A Simple and Accurate Way to Measure AC Current
The ZMCT103C 5A Current Sensor, often seen on the HW670 breakout board, is a compact AC current transformer designed for microcontroller projects — especially Arduino and ESP-based systems.
It lets you safely measure alternating current (AC) without directly connecting your circuit to high-voltage lines — ideal for energy monitoring, automation, and smart metering projects.
“Think of the ZMCT103C as a bridge that lets your Arduino ‘sense’ electricity without getting shocked.”
🧠 How It Works
The ZMCT103C uses the principle of electromagnetic induction — when AC current passes through the input coil, it generates a proportional signal on the secondary side.
That tiny voltage is then amplified and filtered by the HW670 board’s circuitry, making it safe and readable by analog inputs (like A0 on an Arduino).
⚙️ Basic Operation Flow
1️⃣ AC current passes through the primary terminal
2️⃣ The sensor’s magnetic core induces a small current
3️⃣ The onboard amplifier converts it to a measurable voltage
4️⃣ The Arduino reads this voltage and calculates current
“You’re not measuring current directly — you’re measuring its magnetic fingerprint.”
⚡ Key Features
- Measures AC currents up to 5A RMS
- Output voltage range typically 0–1V (centered)
- Fully isolated from the high-voltage circuit
- Compact and easy-to-mount module (HW670 board)
- Works with Arduino, ESP32, STM32, and more
- Perfect for energy meters, current monitoring, and IoT automation
🧩 Technical Specifications
| Parameter | Value |
|---|---|
| Model | ZMCT103C |
| Input Current | 0–5A AC |
| Output Voltage | 0–1V (typical) |
| Accuracy | ±1% (with calibration) |
| Isolation Voltage | 2000V |
| Module Version | HW670 breakout |
| Operating Frequency | 50/60 Hz |
| Operating Voltage (board) | 5V DC |
| Dimensions | 27 × 20 mm (approx.) |
💡 Typical Applications
| Use Case | Purpose |
|---|---|
| Smart energy meters | Track home energy usage |
| IoT monitoring | Cloud-connected current sensing |
| Industrial automation | Detect current draw and load levels |
| Home projects | Measure power consumption safely |
| Solar energy systems | Monitor inverter or grid output |
🔧 How to Connect to Arduino
Example Sketch Snippet
int sensorPin = A0;
float sensorValue;
void loop() {
sensorValue = analogRead(sensorPin);
Serial.println(sensorValue);
delay(500);
}
Once you have readings, apply calibration constants to convert voltage to current (A) using known load values.
🧠 Calibration Tip
Connect a known load (e.g., a 60W bulb at 120V ≈ 0.5A).
Record the output voltage — use this as your reference factor for future measurements.
This ensures your sensor gives accurate, reliable readings in any setup.
💬 In Simple Terms
“The ZMCT103C + HW670 board turns dangerous AC current into a safe signal your Arduino can understand — it’s like giving your circuit an electrical sixth sense.”
It’s small, reliable, and perfect for anyone starting out in IoT energy monitoring or DIY home automation.