On this post, we are going to explain how to do the basics when working with internal relays of Industrial Shields' Programmable Logic Controllers. Reading this post, you will be able to understand how to connect and configure the analog inputs of your industrial Arduino PLC controller.

We recommend you to read the following blogs in order to understand the program of this blog. We used the following blog posts to do this example:

• How to program your industrial PLC with Arduino IDE: Installing the Industrial Shields's boards in the Arduino ID

In order to work with relays, you will need any of our industrial controllers for industrial automation that have relay capabilities.

• Industrial Shields controllers: Wifi & Bluetooth Controller Family, Ethernet Controller Family, GPRS / GSM Controller Family or 20IOs Controller Arduino Family

There are 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 references 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" equival to a relay closed, and "LOW" equival 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 the Ardbox family in 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 the M-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(R_01, HIGH);    
    delay(1000);
    Serial.println("Closing");
    digitalWrite(R_01, LOW);
    delay(1000);
}