How do you design and test a sequential function chart in S7-GRAPH?

1 Install and launch S7-GRAPH

Before you can start designing your SFC, you need to install and launch S7-GRAPH on your computer. You can download the software from the Siemens website, or use the installation CD that comes with your PLC. To launch S7-GRAPH, you need to open the SIMATIC Manager and create a new project, or open an existing one. Then, you need to select the PLC type and the communication settings, and add a new SFC block to your project.

2 Define the steps and transitions

The next step is to define the steps and transitions of your SFC. A step is a state or condition of the PLC program, such as waiting for a sensor signal or activating an output. A transition is a condition or event that triggers the change from one step to another, such as a timer or a switch. To define the steps and transitions, you need to use the S7-GRAPH editor, which has a toolbar and a workspace. You can drag and drop the symbols from the toolbar to the workspace, and connect them with lines.

3 Assign the actions and conditions

After you have defined the steps and transitions, you need to assign the actions and conditions to them. An action is a command or instruction that the PLC executes when a step is active, such as setting or resetting a bit. A condition is a logical expression that determines whether a transition is true or false, such as comparing two values or checking a bit status. To assign the actions and conditions, you need to use the properties window, which shows the details of each symbol. You can enter the action or condition code in the corresponding field, or use the selection list.

4 Compile and download the SFC

The final step is to compile and download the SFC to your PLC. Compiling is the process of converting your SFC code into executable code that the PLC can understand. Downloading is the process of transferring the compiled code from your computer to the PLC memory. To compile and download the SFC, you need to use the menu commands or the toolbar buttons in the S7-GRAPH editor. You also need to make sure that your PLC is connected and switched on.

5 Test and monitor the SFC

Once you have downloaded the SFC to your PLC, you can test and monitor its performance. Testing is the process of verifying that your SFC works as intended and meets the requirements of your application. Monitoring is the process of observing and analyzing the behavior and status of your SFC during operation. To test and monitor the SFC, you need to use the online mode in the S7-GRAPH editor, which allows you to communicate with your PLC in real time. You can use the online functions to start and stop the SFC, force and release the steps and transitions, and view the action and condition values.

6 Modify and optimize the SFC

After you have tested and monitored your SFC, you may want to modify and optimize it. Modifying is the process of changing or adding steps, transitions, actions, or conditions to your SFC, according to your feedback or new requirements. Optimizing is the process of improving the efficiency and performance of your SFC, by reducing the complexity or eliminating the errors. To modify and optimize your SFC, you need to use the offline mode in the S7-GRAPH editor, which allows you to edit your SFC code without affecting your PLC. You can use the offline functions to insert, delete, move, or copy symbols, and to check the syntax and consistency of your code.