A Single Channel Relay Module is an electromechanical switch that allows a low-power microcontroller (like Arduino, ESP32, Raspberry Pi) to safely control high-voltage devices such as lights, fans, motors, and appliances. 🔹 Key Features: Relay Type: SPDT (Single Pole Double Throw) – 1 relay per module Operating Voltage: Common versions are 5V and 12V (coil voltage) Control Signal: Works with 3.3V or 5V logic, so it’s compatible with Arduino and Raspberry Pi Load Capacity: Up to 250V AC / 10A Up to 30V DC / 10A Isolation: Often includes an optocoupler for electrical isolation between control side (Arduino) and load side (AC mains) Indicator LED: Shows relay status (ON/OFF) Triggering: Can be LOW-triggered or HIGH-triggered depending on module design 🔹 Pinout (Typical 5V Single Channel Relay Module): VCC → +5V supply GND → Ground IN → Control signal (from Arduino GPIO pin) Relay Output Pins: COM (Common) – Middle terminal NO (Normally Open) – Connected to COM when relay is ON NC (Normally Closed) – Connected to COM when relay is OFF 🔹 How it Works: When the control pin (IN) receives a HIGH/LOW signal, the relay coil energizes. This closes (or opens) the switch between COM and NO/NC, allowing a high-voltage circuit to be controlled. The low-power microcontroller never directly touches the high-voltage line — it only controls the relay. 🔹 Applications: Smart home automation (lights, fans, appliances) Industrial control systems IoT projects (Wi-Fi or GSM-controlled switches) Motor control Safety switching between circuits