Integrating PLC with SCADA: Real-Time Data Upload

Using Siemens PLC to integrate with SCADA systems for data collection, alarms, and remote control, the core of industrial automation. Today, I’ll teach you how to master it!

Project Requirements and Functionality

The main requirements for this project are:

1. Enable real-time data interaction between PLC and SCADA systems, such as device status, temperature, pressure, etc.
2. Support remote control of PLC by SCADA systems, such as starting or stopping devices.
3. Display alarm information on the SCADA interface, triggering audible and visual alarms during device anomalies.
4. Ensure stable data uploads, with automatic recovery in case of communication interruptions to prevent data loss.
5. Real-time display of PLC operational status on the SCADA interface for easy monitoring and management by operators.

Implementation Logic Breakdown

The entire SCADA system integration logic can be divided into the following parts:

• Communication Initialization Logic: Set the communication parameters of the PLC to establish a proper connection with the SCADA system, such as IP address and port number.
• Data Collection Logic: PLC collects real-time data from on-site devices, such as operational status, temperature, pressure, etc.
• Data Upload Logic: Send the collected data to the SCADA system via Ethernet or Modbus protocol.
• Remote Control Logic: The SCADA system sends commands to the PLC, such as start/stop signals, and the PLC controls the on-site devices based on these commands.
• Alarm Handling Logic: When the device operates abnormally, the PLC sends an alarm signal to the SCADA system, triggering an interface alarm.

Code Implementation

Below is the ladder diagram code for integrating PLC with SCADA using Siemens S7-1200, featuring clear logic and ease of use.

1. Input/Output Allocation Table

First, organize resource allocation for clearer subsequent operations.

2. Communication Initialization Logic

Use the PLC communication function block (TCON) to configure communication parameters, such as IP address and port number, to establish a connection with the SCADA system.

| TCON_INIT
|---| |-------( )---|   // Initialize communication connection  

Set the PLC’s local IP address and the SCADA system’s target IP address in the TCON block to ensure a smooth communication channel.

3. Data Collection Logic

The PLC collects real-time data from on-site devices, such as temperature and pressure, storing the data in a data block, ready for upload to the SCADA system.

| AIW0       DB1.DBD0
|---|MOV|------( )---|   // Write temperature sensor data to data block  

| AIW2       DB1.DBD4
|---|MOV|------( )---|   // Write pressure sensor data to data block  

4. Data Upload Logic

Upload the collected data to the SCADA system via Ethernet for monitoring purposes.

| DB1.DBD0   T_SEND
|---|MOV|------( )---|   // Send temperature data to SCADA via Ethernet  

| DB1.DBD4   T_SEND
|---|MOV|------( )---|   // Send pressure data to SCADA via Ethernet  

5. Remote Control Logic

The SCADA interface sends remote start/stop commands to the PLC, which controls the on-site devices accordingly.

| DB1.DBX0.0   Q0.0
|---| |-------( )---|   // Control on-site device based on SCADA start/stop command  

6. Alarm Handling Logic

When the collected device parameters exceed the set range, trigger an alarm signal and upload the alarm information to the SCADA system.

| AIW0       L#80.0    Q0.1
|---|>|-------(S)---|   // Trigger alarm if temperature exceeds 80℃  

| AIW2       L#150.0   Q0.1
|---|>|-------(S)---|   // Trigger alarm if pressure exceeds 150  

| Q0.1       T_SEND
|---| |-------( )---|   // Send alarm signal to SCADA via Ethernet  

7. Status Display Logic

Write the communication status and data upload status to the HMI for operators to monitor the system’s operational status in real time.

| TCON_STATUS  DB1.DBX0.1
|---| |-------( )---|   // Write SCADA communication status to HMI  

| T_SEND_STATUS  DB1.DBX0.2
|---| |-------( )---|   // Write data upload status to HMI  

Optimization and Common Issues

1. Communication Interruption Issue: Unstable networks may cause communication interruptions. You can add reconnection logic and regularly send heartbeat packets to check communication status.
2. Data Loss Issue: If the SCADA receiving frequency is low, it may lead to data loss. Consider adding a caching feature to send data in batches.
3. False Alarm Issue: Signal fluctuations from sensors may trigger false alarms. You can add signal filtering or delay confirmation logic.
4. IP Conflict Issue: The IP addresses of the PLC and SCADA must not overlap. Careful checking of network configurations during programming is necessary.

Complete Code Framework

Below is the complete ladder diagram code framework:

| TCON_INIT                                // Initialize communication
|---| |-------( )---|  

| AIW0       DB1.DBD0                    // Data collection
|---|MOV|------( )---|  

| AIW2       DB1.DBD4
|---|MOV|------( )---|  

| DB1.DBD0   T_SEND                     // Data upload
|---|MOV|------( )---|  

| DB1.DBD4   T_SEND
|---|MOV|------( )---|  

| DB1.DBX0.0   Q0.0                     // Remote control
|---| |-------( )---|  

| AIW0       L#80.0    Q0.1             // Temperature alarm
|---|>|-------(S)---|  

| AIW2       L#150.0   Q0.1             // Pressure alarm
|---|>|-------(S)---|  

| Q0.1       T_SEND                    // Alarm upload
|---| |-------( )---|  

| TCON_STATUS  DB1.DBX0.1              // Communication status display
|---| |-------( )---|  

| T_SEND_STATUS  DB1.DBX0.2            // Data upload status display
|---| |-------( )---|  

Conclusion

Integrating PLC with SCADA focuses on communication and data synchronization—write it clearly to avoid confusion! If you have any questions, feel free to leave a message, and we can research together!