Additional application examples
Further Information
Refer also to the application example found in the overview for this function block.
This section describes an additional possible application, where the function block evaluates a mode selector switch.
The function block must only be used in an actual application once a risk analysis has been conducted.
Details of the risk category/SIL/PL have not been included here, as classification is always based on the application in which the function block is used.
NOTE:
The use of the safety-related function block alone is not sufficient to execute the safety-related function according to the Cat./SIL/PL determined by the risk analysis. In conjunction with the safety-related I/O device used, additional measures must be taken to meet the requirements of the safety-related function. These include, for example, the appropriate wiring and parameterization of the inputs and outputs as well as measures to exclude (design out) errors that cannot be detected. For additional information, refer to the documentation provided with the safety-related I/O device used.
NOTE:
Refer to the notes in the User Manual on proper electrical connection of the Safety Logic Controller and the extension modules (e.g., connecting the mode selector switch).
Operating mode selection with locking of the set operating mode and manual operating mode confirmation
This example uses a three-stage mode selector switch S1 to show how operating modes are selected. In order to operate the controlled machine in operating mode 2 (in the example shown, this is setup mode) or 3 (manual mode), the selected mode must be enabled manually by pressing an enable switch. This enable switch is evaluated via the safety-related SF_EnableSwitch function block.
Connecting the SF_ModeSelector function block:
The function block is perpetually activated by the TRUE constant at the Activate input.
The mode selector switch S1 to be evaluated is connected to the input terminals I0 to I2 of the safety-related input device SDI 1. The signals are assigned to the global I/O variables and the function block inputs are connected as follows:
|
Terminal |
Global I/O variable |
Function block input |
|
I0 |
S1_State0_In |
S_Mode0 |
|
I1 |
S1_State1_In |
S_Mode1 |
|
I2 |
S1_State2_In |
S_Mode2 |
A key switch S2 is connected to input terminal I3 of the safety-related input device SDI 1. The signal is assigned to the global I/O variable S2_LockMode_In, which in turn is connected to the S_Unlock input of the SF_ModeSelector function block. Locking the key switch (S_Unlock = SAFEFALSE) locks the operating mode that has been set.
The AutoSetMode input is set to FALSE, which means that manual confirmation of the set operating mode is required at the S_SetMode input. A button S3 is connected to the input terminal I4 of the safety-related input device SDI 1 for this purpose. The signal is assigned to the global I/O variable S3_SetMode_In, which in turn is connected to the S_SetMode input of the function block.
The signal of reset button S4 connected to input terminal NI0 of the standard input device DI1 is used for resetting error messages (positive signal edge at the Reset function block input) of both safety-related function blocks and for removing the restart inhibit of the SF_EnableSwitch function block. For this reason, the global I/O variable S4_Reset is assigned to the function blocks SF_EnableSwitch and SF_ModeSelector.
The use of enable outputs S_Mode0Sel to S_Mode2Sel is described in the notes below.
Connecting the SF_EnableSwitch function block:
The SF_EnableSwitch function block evaluates an S5 enable switch connected to the Safety Logic Controller. The S_EnableSwitchOut enable output can only become SAFETRUE if input S_SafetyActive = SAFETRUE (see note below). This depends on the other input signals.
The function block is perpetually activated by the TRUE constant at the Activate input.
The three-stage enable switch S5 is connected to input terminals I5 and I6 of the safety-related input device SDI 1.
The two signals are connected to the S_EnableSwitchCh1 and S_EnableSwitchCh2 inputs of the function block via the global I/O variables S5_SwitchCH1_In and S5_SwitchCH2_In.
A restart inhibit is set via S_AutoReset of the SF_EnableSwitch function block. This inhibit becomes active after a valid signal sequence returns at the function block inputs S_EnableSwitchCh1 and/or S_EnableSwitchCh2. The restart inhibit is removed via the shared Reset button S4 (see above).
NOTE:
Notes on the graphic:
The S_Mode0Sel to S_Mode2Sel enable signals of the SF_ModeSelector function block have the following functions:
(1): Automatic mode.
(2): Setup mode. Request for the safely reduced speed at the speed monitor.
(3): Manual mode.
Connecting the SF_EnableSwitch function block:
(4): The S_SafetyActive input of the SF_EnableSwitch function block is connected to the feedback signal of the speed monitor. This feedback signal is used to set the selected operating mode (reduced speed).
(5): The S_EnableSwitchOut enable signal of the SF_EnableSwitch function block is connected to other safety-related function blocks or functions and controls the application accordingly.
|
S1 |
Mode selector switch with 3 switch positions |
|
S2 |
Key switch (blocking the mode selection) |
|
S3 |
Confirmation |
|
S4 |
Reset |
|
S5 |
Three-stage enable switch |
|
|
See note above the illustration. |
