Arduino Relay module interfacing
Relay modules are assembled units commonly included with Optocouplers, diodes, LED’s, transistors, etc.. So, for the Arduino interfacing we just have to connect a supply voltage, GND and input signal connection.
An input section of the relay module consists of three terminals VCC and GND and a signal input (IN1).
If the load connection is between the COM and NC, the terminals will be closed for LOW state input signal and open during HIGH state input. Inversely, the HIGH state closes and LOW state opens for a connection between COM and NO.The output contacts of the module have three connections, labelled as Common (COM), Normal close (NC) and Normal open (NO).
The pin arrangements of the relay modules may be different from one another. The chance of damage to the module due to wrong connection is considerable, so check the label of each pin and ensure the contacts are correct.
Multi-channel Relays can be interfaced in the same way, Only additional input pins IN1, IN2, IN3,etc., need to be connected to the module, from the Arduino outputs.
For 12V or high power relays external DC supply is required. While using external supply common ground terminals should be connected to the module and the Arduino.