16-Channel Relay Board Module, Active-Low

Features

• Good in safety. In power system and high voltage system, the lower current can control the higher one, able to control various appliances and other equipment with high-current current.
• Standard interface that can be controlled directly by microcontroller (Arduino, 8051, AVR, PIC, DSP, ARM, ARM, MSP430, TTL logic).
• Indication LEDs for Relay output status.
• With a normally-open (NO) and a normally-close (NC) contact.

Specification

• Number of Relays: 16
• Control signal: TTL level
• Rated load: 7A/250VAC; 10A/125VAC; 10A/28VDC;
• Contact action time: 10ms/5ms
• Current: 15-20mA per channel
• Dimension: 133mm (L) * 55mm (W) * 19mm (H)

Below is an example for 4-channel relay board:

Pin definition

• COM - Common pin: This is source pin, that starts connected to NC, and connects to NO when you apply 0v / GND (active low)
• NC (Normally Closed): in which case NC is connected with COM when INT1 is set low and disconnected when INT1 is high;
• NO (Normally Open): in which case NO is disconnected with COM1 when INT1 is set low and connected when INT1 is high.
• INT 1- Relay 1 control port: changes from the COM–>NO to the COM–>NC when you apply 0v / GND (active low)
• INT 2- Relay 2 control port: changes from the COM à NO to the COM à NC when you apply 0v / GND (active low)

Above: Example of connecting power and lights to a relays COM and NO connectors.  

The Sketch

Enter the following sketch, upload it and go to town.
If you open your Arduino serial monitor you will be able to see the progress.

// Basic 4 Realy board connection
// Each relay is turned on for 2 seconds and then off.
// You can here them click as there state changes from off to on and on to off.
// You will also see the corresponding Red LED on the 4 Relay board light up when the relay is on.
// Define names for the 4 Digital pins On the Arduino 7,8,9,10
// These data pins link to 4 Relay board pins IN1, IN2, IN3, IN4

#define RELAY1  6                        
#define RELAY2  7                        
#define RELAY3  8                        
#define RELAY4  9

void setup(){    
// Initialise the Arduino data pins for OUTPUT
  pinMode(RELAY1, OUTPUT);       
  pinMode(RELAY2, OUTPUT);
  pinMode(RELAY3, OUTPUT);
  pinMode(RELAY4, OUTPUT);
}

void loop(){
   digitalWrite(RELAY1,LOW);           // Turns ON Relays 1
   delay(2000);                                      // Wait 2 seconds
   digitalWrite(RELAY1,HIGH);          // Turns Relay Off

   digitalWrite(RELAY2,LOW);           // Turns ON Relays 2
   delay(2000);                                      // Wait 2 seconds
   digitalWrite(RELAY2,HIGH);          // Turns Relay Off

   digitalWrite(RELAY3,LOW);           // Turns ON Relays 3
   delay(2000);                                      // Wait 2 seconds
   digitalWrite(RELAY3,HIGH);          // Turns Relay Off

   digitalWrite(RELAY4,LOW);           // Turns ON Relays 4
   delay(2000);                                      // Wait 2 seconds
   digitalWrite(RELAY4,HIGH);          // Turns Relay Off        
}

Video:

• Relay Video Explanation: http://www.youtube.com/watch?v=YJNUe65BVM0
• Using Relays and Relay Boards with the Raspberry Pi - http://www.youtube.com/watch?v=b6ZagKRnRdM