Nexto XF – #13 Creating Seal Logic

The objective of this tutorial is to create a seal logic in a MasterTool X project.

Components

Equipment: 1 computer/notebook.

Software: MasterTool X

Tutorial Sections

1. ARCHITECTURE
2. DEVELOPMENT

1. ARCHITECTURE

A computer/notebook will be required to use MasterTool X.

Figure 1. Computer running MasterTool X

2. DEVELOPMENT

Seal logic is one of the most widely used structures in industrial automation. It allows an output to remain activated even after the initial command is released, being deactivated only when a specific condition occurs (usually a stop button).

Concept of Sealing Logic

Sealing logic is basically formed by:

• Normally open (NO) contact → start command
• Normally closed (NC) contact → stop command
• Coil → output to be kept on
• Contact in parallel to the NO, with the same address as the coil → responsible for the seal

When the start contact is activated, the coil energizes. The parallel contact, connected to the same variable as the coil, keeps the circuit active even after the start contact returns to the open state.

Inserting contacts into the networ

With UserPrg open, select the logic line (Network) where the condition will be created.

The normally open contact can be inserted into the network in the following ways:

• Context menu:
  Right-click on the network and select Insert Contact.
• Top toolbar:
  With the network selected, click on the Insert Contact command.
• Toolbox (right side of the screen):
  Access the Ladder Elements tab and select and drag it to the Contact code line.
• Keyboard shortcut:
  With the network selected, press Ctrl + K.

Figure 2. Inserting the open contact to build the Seal logic

Inserting the normally closed (NC) contact

The normally closed (NC) contact can be inserted using the same menus as the normally open (NO) contact:

• Context menu (right-click on the network)
• Top toolbar
• Toolbox (right side of the screen)

The difference is that the NC contact does not have a dedicated keyboard shortcut.

In addition, MasterTool IEC XE offers a practical way to change the type of the already inserted contact:

1. Insert a normally open (NO) contact into the network.
2. Right-click on the contact.
3. Select the Negation option.

When applying negation, the software inverts the contact type:

• A normally open (NO) contact becomes normally closed (NC)
• An NC contact becomes normally open (NO)
   

This feature facilitates adjustments to the logic without the need to remove and reinsert the contact, making editing faster and more organized.

Figure 3. Inserting the negated contact to build the Seal logic

Inserting the coil

The coil can be inserted:

• Through the context menu
• Through the top bar
• Through the toolbox
• Using the shortcut Ctrl + A

Associate the coil with the output variable that will be sealed.

Figure 4. Inserting the coil to build the Seal logic

Inserting the seal contact (in parallel)

1. Select the normally open starting contact.
2. Use the Insert Parallel Contact Below option, available:
   • In the top menu
   • In the context menu (right-click)
   • Shortcut CTRL + R
   • Toolbox (Parallel Contact)
3. Associate this contact with the same variable as the coil.

This contact is responsible for the self-maintenance of the logic.

Figure 5. Inserting a parallel contact to build the Seal logic

Operation of the seal logic

• When the start contact (NO) is activated, the coil energizes.
• The parallel contact (seal) closes, keeping the coil energized.
• When the start contact is released, the seal keeps the circuit energized.
• When the stop contact (NC) is activated, the circuit is interrupted and the coil turns off.

Testing the logic

After assembling the seal logic:

1. Download the application.
2. Put the CPU in RUN mode.
3. Manipulate the variables of the start and stop contacts.
4. Observe the behavior of the coil and the sealing contact in the Ladder logic.

This test confirms the correct operation of the sealing logic, widely used for motor actuation, retention systems, and on/off commands.

Figure 6. Operation of the Sealing Logic