Learning the basics about internal relays of an industrial PLC

There is only one kind of relay in our PLC. These relays have the following characteristics:

• Up to 5A working up to 250Vac

• Up to 3A working up to 30Vdc

The next draw shows how to identify the relays GPIO:

The internal relays do not have polarity. They must be connected like this:

To program the internal relays, we must keep in mind we can write the values using the following command:

digitalWrite(relay,value);

"Relay" must be the reference of the objective relay. The Ardbox family has the reference as "R1", and for example, the M-Duino family has the reference as "R0.1" with the relay.  We must write "HIGH" or "LOW" in the "value" parameter. "HIGH" is equivalent to a relay closed, and "LOW" is equivalent to an opened relay.

digitalWrite(R1,HIGH);    // Ardbox family
digitalWrite(R0_3,LOW);   // M-Duino family     

You can see how to handle an internal relay in theArdbox familyin the next example below:

// Internal relay example in Ardbox family
// This example writes the R1 and shows via serial the state

// Setup function
void setup()
{
    // Set the speed of the serial port
    Serial.begin(9600UL);
}

// Loop function
void loop()
{
    Serial.println("Opening");    
    digitalWrite(R1, HIGH);    
    delay(1000);
    Serial.println("Closing");
    digitalWrite(R1, LOW);
    delay(1000);
}

The next one shows how to handle an internal relay in theM-Duino family:

// Internal relay example in M-Duino family
// This example writes the R0_1 and shows via serial the state

// Setup function
void setup()
{
    // Set the speed of the serial port
    Serial.begin(9600UL);
}

// Loop function
void loop()
{
    Serial.println("Opening");    
    digitalWrite(R0_1, HIGH);    
    delay(1000);
    Serial.println("Closing");
    digitalWrite(R0_1, LOW);
    delay(1000);
}