SF_TwoHandControlTypeII

The following description is valid for the function block SF_TwoHandControlTypeII_V1_0z, Version 1.0z (where z = 0 to 9).

Short description

The safety-related SF_TwoHandControlTypeII function block evaluates the switching behavior of a type II two-hand control device connected to the Safety Logic Controller.

This involves evaluating the switching states of both the buttons on the two-hand control device. The S_TwoHandOut output only becomes SAFETRUE if both inputs switch from SAFEFALSE to SAFETRUE, either simultaneously or consecutively (if both buttons on the two-hand control device are pressed after being not actuated before).

NOTE:

Unlike the type III two-hand control device, type II does not evaluate whether both buttons are actuated within a period of 500 ms.

NOTE:

The used type II two-hand control device must comply with the requirements set out by EN 574.

Function block inputs

Click the corresponding hyperlinks to obtain detailed information on the items below.

Name	Short description	Value
Activate	State-controlled input for activating the function block. Data type: BOOL Initial value: FALSE NOTE: While function block activation is taking place (with input Activate = TRUE), both inputs must show the SAFEFALSE state. This means that none of the buttons on the two-hand control device must be actuated. Otherwise, the function block detects this as an error (output Error = TRUE).	FALSE: Function block inactive TRUE: Function block activated
S_Button1 and S_Button2	State-controlled inputs for evaluating the connected two-hand control device. Data type: SAFEBOOL Initial value: SAFEFALSE	SAFEFALSE: Button not pressed SAFETRUE: Button pressed

Function block outputs

Name	Short description	Value
Ready	Output for signaling "Function block activated/not activated". Data type: BOOL	FALSE: Function block is not activated (Activate = FALSE) and all outputs of the function block are switched to FALSE/SAFEFALSE. TRUE: Function block is activated (Activate = TRUE) and the output parameters represent the state of the safety-related function.
S_TwoHandOut	Control signal for stopping (stop request) or starting and maintaining machine operation. Data type: SAFEBOOL	SAFEFALSE: S_TwoHandOut switches to SAFEFALSE if the function block has not been activated or the buttons have not been actuated or have been actuated incorrectly or an error has been detected. SAFETRUE: S_TwoHandOut is SAFETRUE if the function block has been activated and the buttons have been actuated correctly and no errors have been detected.
Error	Output for error message. Data type: BOOL	FALSE: No error is present. TRUE: The function block has detected an error: During function block activation (with input Activate = TRUE), at least one input was in the SAFETRUE state. The S_TwoHandOut output switches to SAFEFALSE as a result. To leave the error state, both inputs S_Button1 and S_Button2 must show the SAFEFALSE state.
DiagCode	Output for diagnostic message. Data type: WORD	Diagnostic message of the function block. The possible values are listed and described in the topic "Diagnostic codes".

Signal sequence diagram

This diagram is based on a typical type II two-hand control application.

NOTE:

The signal sequence diagrams in this documentation possibly omit particular diagnostic codes. For example, a diagnostic code is possibly not shown if the related function block state is a temporary transition state and only active for one cycle of the Safety Logic Controller.

Only typical input signal combinations are illustrated. Other signal combinations are possible.

0	The function block is not yet activated (Activate = FALSE). As a result, all outputs are FALSE or SAFEFALSE.
1	Function block activated by Activate = TRUE. At this point, the two buttons are not actuated (S_Button1 and S_Button2 = SAFEFALSE). Both inputs must be SAFEFALSE during activation of the function block, so the Error output remains FALSE.
2	If both buttons are actuated, inputs S_Button2 and S_Button1 change one after the other from SAFEFALSE to SAFETRUE. When S_Button1 switches to SAFETRUE, the condition for two-hand control is met and the S_TwoHandOut output becomes SAFETRUE.
3	The S_TwoHandOut output becomes SAFEFALSE, as S_Button1 switches to SAFEFALSE (button is released).
4	Although the button at S_Button1 is now actuated again, the S_TwoHandOut output remains SAFEFALSE, as a change in state has only occurred at input S_Button1, with input S_Button2 remaining SAFETRUE throughout.
5	The function block is deactivated: Activate switches to FALSE. While the function block is inactive, S_Button2 returns to SAFEFALSE (button 2 is released). This change in state has no effect on the function block outputs, as the function block is not activated.
6	Function block is activated again (Activate becomes TRUE again). The signal combination at the inputs (S_Button1 = SAFETRUE and S_Button2 = SAFEFALSE) at the time when the function block is activated again leads to an error message (Error = TRUE, S_TwoHandOut = SAFEFALSE). Both inputs must be SAFEFALSE when the function block is being activated.
7	The error message is "reset", as S_Button1 and S_Button2 are now in the SAFEFALSE state (neither button is actuated).
8	Both buttons are actuated again, the condition for two-hand control is met, and S_TwoHandOut switches to SAFETRUE again.

Application example

This example shows the connection of a type II two-hand control device with the safety-related SF_TwoHandControlTypeII function block.

Each of the two buttons has both an N/C and an N/O contact and is connected to safety-related input device SDI 1 via a two-channel arrangement.

The two resulting signals monitored for antivalence are each assigned to global I/O variables and connected to the function block inputs S_Button1 and S_Button2 for evaluation

Further Information:

The details and notes for this application example must also be taken into account.

NOTE:

The S_TwoHandOut enable output of the SF_TwoHandControlTypeII function block is connected to an output terminal of the application via a global I/O variable or via other safety-related functions/function blocks.

Connect the S_TwoHandOut enable output of the SF_TwoHandControlTypeII function block to the S_OutControl input of the SF_EDM function block, for example, thus implementing a two-channel output connection.

Further Information:

For more detailed information, refer to the description of the corresponding safety-related function block.

NOTE:

The SF_TwoHandControlTypeII function block must not be activated by means of a TRUE constant at its Activate input, but the activation must be done by the application of the higher-level standard controller.

Possible measure for the activation of the SF_TwoHandControlTypeII function block at its Activate input:

At each device involved in the safety-related function, one input is fixed to "1". These inputs are AND combined and then used for activating the safety-related function. The safety-related function is not activated until all safety-related devices involved deliver valid process data. For that purpose, one safety-related input must be used per input module. With this measure, operation with partial configurations is possible.

S1	Button 1
S2	Button 2
	See second note above the illustration.

Detailed information

Additional information is available in the following sections: