4 Channel Relay Shield Arduino compatible

I've used this relay shield for a personal project, the quality of the boards was pretty fine but there was no documentation supplied except for an image or two on the original web site.

Module features are :

1. Standard for Arduino Shield interfaces and shape.
2. Can continue to stack other for Arduino expansion board (relays use Digital output Pins 7,6,5 and 4). Also the SPI connector is stackable
3. 3x M3 screw positioning holes for easy installation.
4. High Drive (5V or 3.3V) normally open contact closure.
5. 4 red led Onboard relay indicator

Special Note: If mounting on an Arduino Uno, take care about the pins of the green terminal blocks do not interfere with the USB interface (which is higher than normal).

Relay Shield Interface:

• Relay: sky- 5V DC relay , model HJR-4102-L-5V, 
• Power Interface : 5V DC power interface
• Indicator: four leds are red when the relay is driven high , the corresponding indicator will light up .
• Relay Terminals: Terminal high-power , high-current high voltage can be connected to the device - 3A 125VAC - 3A 24VDC

Here a simple example's sketch:

void setup () 

  { 

    pinMode (4, OUTPUT); 

    digitalWrite (4, LOW );

    pinMode (5, OUTPUT); 

    digitalWrite (5, LOW );

    pinMode (6, OUTPUT); 

    digitalWrite (6, LOW );

    pinMode (7, OUTPUT); 

    digitalWrite (7, LOW );

    pinMode (13, OUTPUT); 

    delay (5000);

 }

void loop () 

{ 

    

    digitalWrite (4, HIGH );

    digitalWrite (5, HIGH );

    digitalWrite (6, HIGH );

    digitalWrite (7, HIGH );

    digitalWrite (13, HIGH );

    delay (1000);

    digitalWrite (4, LOW );

    digitalWrite (5, LOW );

    digitalWrite (6, LOW );

    digitalWrite (7, LOW );

    digitalWrite (13, LOW );

    delay (1000);

    

}