This is a 5V 2ch RobotDYN relay interface board. It can be used to control a variety of high-current appliances and equipment. It has high-current relays that operate at AC250V 10A or DC30V 10A and a standard interface that can be controlled directly by the microcontroller.. optical isolators are built into the module. it keeps high voltage from affecting the system receiving the signal.

Package Includes:

• 1 x 2ch RobotDYN Relay Module Low Trigger

Features:

• Each relay features an LED indicator
• Color: Black
• Optocoupler included on the board for reducing the distortion.
• One normally closed contact and one normally open contact
• High-impedance controller pin
• Power supply indicator and Control indicator lamp
• The power source can be configured with a jumper located on the board.

Description:

This is a 5V 2ch RobotDYN relay interface board, It can be used to control a variety of high-current appliances and equipment. It has high-current relays with a standard interface that can be controlled directly by the microcontroller. optical isolators are built into the module. it keeps high voltage from affecting the system receiving the signal. An optocoupler is a component that uses light to transfer electrical signals between two states of isolation circuits while preventing high voltage from affecting the receiving system. The relay's maximum contact is AC250V 10A and DC30V 10A, and microcontrollers can be connected directly to the standard interface. Safety features are provided by red working status indicator lights. MCU control, industrial sector control, PLC control, and intelligent home control are all common applications.

Principle of Work:

A relay is a type of switch that can be controlled with an electrical signal. It is a way to open or close a circuit in this case via a signal from the connected microcontroller. The relay isolates the circuit on the device you want to control from the device that's controlling it. and low-level triggered will allow the current to go through the power line when the control signal is GND or close. optocoupler on the other hand makes real photo isolation between the relay and the MCU which is very good to minimize the distortion from the other side

Pinout of the Module:

GND - Connect 0V of the external Power Supply.

SGND - Connect 0V of the Arduino.

IN1 - Controls Relay 1, active Low! The relay will turn on when this input goes below about 2.0V

IN2 - Controls Relay 2, active Low! The relay will turn on when this input goes below about 2.0V

VCC - Connect 5V to this pin. Is used to power the optocouplers

NC: you connect your application here if you want it to be working all the time and stop when you attach input to GND

COM: common always connected

Applications:

• Relay Drive from External Contacts.
• LED Series and Parallel Connections.
• Electronic Circuit Drive by Means of a Relay.
• Home automation
• Battery backup
• High current load switching

Circuit:

Two distinct loads have been connected to the relay's NO terminals. Each relay's common terminal has a live wire connected to it. When the relays are activated, the load is powered and connected to the live wire. This configuration can be reversed by connecting the load to the NC terminal, which keeps the load powered on until the relay is activated.

Library:

This Module doesn't need a library to work.

Code:

void setup() {
 // initialize digital pin LED_BUILTIN as an output.
 pinMode(2, OUTPUT);
 pinMode(3, OUTPUT);

digitalWrite(2, HIGH);
digitalWrite(3, HIGH); 


}
// the loop function runs over and over again forever
void loop() {
 digitalWrite(2, LOW); // turn the LED ON by making the voltage LOW delay(1000);
 delay(1000); // wait for a second 
 digitalWrite(3, LOW); // turn the LED ON by making the voltage LOW delay(1000); 
 delay(1000); // wait for a second 

 digitalWrite(2, HIGH); // turn the offon (HIGH is the voltage level)
 delay(1000); // wait for a second 
 digitalWrite(3, HIGH); // turn the offon (HIGH is the voltage level) 
 delay(1000); // wait for a second 
 
}

Technical Details:

• 2 Channel
• Supply voltage – 3.3V to 5V
• Trigger current – 5mA - 15mA
• Relay maximum contact voltage – 250VAC, 30VDC
• Relay maximum current – 10A

Resources:

 Tutorial 1

Comparisons:

Using an Active Low Triggered Relay Module comes with a price that you need to use a current to keep the application off on the other side of the relay or you can use this board with the application were required to be on all the time and turn it off less often or simple you can connect the application on the NO side instead of the normal connecting. the optocoupler on the other hand is very useful this device lowers the distortion from the power lines and makes the circuit more isolated and better than the boards where no such a device is included so you need always to connect the GND of the MCU GND of the circuit which is not very good idea sometimes.

This kind of relay board has so many advantages like being able to withstand large inrush currents and high mechanical structure reliability, not being susceptible to the external electromagnetic environment, and being able to carry high voltage, and high current load but still, it has multiple disadvantages to the SSR Boards that they are slower than SSRs at 5 to 15ms and it has a larger package size, is not suitable for small projects and electromechanical relays tend to have a shorter life than other types of relays due to mechanical wear if you interested in SSRs you can get it from here