Use Boolean controls and indicators located on the Boolean subpalettes to enter and display Boolean (TRUE/FALSE) values with objects such as buttons, switches, and LED lights.

The following list describes the common use cases of Boolean controls and indicators on the Controls palettes in LabVIEW.

Note The availability of Boolean controls and indicators might vary depending on the subpalette style you choose.
  • Button—Use as a control to select a command by depressing the button.
  • Rocker—Toggle—Switch—Use as a control. Select a command by rocking, toggling, or switching the object from one position to the other.
  • LED—Use as an indicator. Display that a condition is met. LabVIEW turns the light ON or OFF depending on whether the condition is met.
  • Radio buttons—Use as a control. Select a command from a list of choices.
  • Checkbox—Use as a control. Select a TRUE or FALSE state, such as when only one option is possible.
  • Mixed checkboxes—(System palette only) Use as a control. Select a TRUE, FALSE, or MIXED state, such as when simultaneously setting a property of multiple objects where some are TRUE and FALSE.

    • Mechanical Actions of Boolean Controls

    In LabVIEW, Boolean controls have a configurable mechanical action that lets them resemble the behavior of physical instruments, such as oscilloscopes and multimeters.

    There are two general categories of mechanical action: switch and latch. Switch and latch actions are similar in that they both change the value of the Boolean control. The actions differ in how the value of the control reverts to the previous value.

  • Switch action—Allows only the user to revert the value of the control back to the previous value.
  • Latch action—Allows the VI that reads the control to revert the value of the control back to the previous value. Also allows the user to return the value of the control to the previous value, but only if the user does so before the VI reads the control.
    Note Latch actions cannot be used with local variables. Latch actions used with event structures typically have their terminals placed inside the Value Change event frame.

    • To define the mechanical action for a Boolean control, right-click the control and select the behavior from the Mechanical Action menu. Table 3. Boolean Control Mechanical Actions provides more information about the three types of switch behaviors and latch behaviors:

    Table 3. Boolean Control Mechanical Actions
    Behavior When to Use Example
    Switch When Pressed
    • Changes the current value as soon as you click the control.
    • Retains the new value until you click the control again.
    		 Light switch: The light turns on as soon as you switch the control. The light stays in that state until you switch the control again.
    Switch When Released
    • Changes the current value when you release the mouse button.
    • Retains the new value until you click the control again.
    		 Checkbox: The checkbox changes its value only after you release the mouse button. This gives you the ability to reconsider your choice after clicking by moving the cursor away from the checkbox before releasing the mouse button.
    Switch Until Released
    • Changes the current value only when you click and hold the mouse button down.
    • Reverts to the previous value when you release the mouse button.
    		 Doorbell: The bell rings as soon as you press the button. The bell continues to ring until you release the button.
    Latch When Pressed
    • Changes the current value as soon as you click the control.
    • Reverts to the previous value after the VI reads the control.
    		 Emergency stop button: The button stops the system as soon as you press the button. The button resets as soon as the system reads the change in value, allowing for the button to be pressed again.
    Latch When Released
    • Changes the current value when you release the mouse button.
    • Reverts to the previous value after the VI reads the control.
    		 Close button: The button closes the program only after you release the mouse button and the application reads the change in value. This gives you the ability to reconsider your choice after clicking by moving the cursor away from the button before releasing the mouse button.
    Latch Until Released
    • Changes the current value only when you click and hold the mouse button down.
    • Once you release the mouse button, the value will revert to the previous value after the VI reads the control.
    		 Robot movement control: The movement control informs the system of the robot to move the robot while the control is pressed down. Once the control is released, and the system of the robot has read the control, the robot goes back to its previous state of non-movement.
    Note (FPGA Module) On FPGA targets, use Switch When Pressed, Switch When Released, or Switch Until Released as a control that changes the current value once a new value is written from the host VI to the FPGA target, and retains the new value until another value is written from the host VI again. Use Latch When Pressed, Latch When Released, or Latch Until Released as a control that only changes the current value when a new value is written from the host VI to the FPGA target, and reverts to the previous value once the new value has been read by the FPGA target.