Display Current Logged-In User on WinCC Flexible HMI Panels

Engineers commissioning Siemens panels in WinCC Flexible 2008 or WinCC Flexible 2005 frequently need to expose the currently logged-in operator to the connected PLC so that recipe edits, parameter changes, alarm acknowledgments, and audit-trail entries can be recorded against a specific user account. WinCC Flexible already maintains a complete local user administration database, but the runtime does not automatically mirror that state to the controller. This guide documents a working scheduler-driven VBScript pattern, the underlying HMI-to-PLC tag architecture, the cause of the most common SmartTags("System\LOGIN_NotLoggedIn") compile error, and the alternate single-bit boolean status approach for projects with very limited tag budgets. Every function name, event name, and parameter is consistent with the WinCC Flexible runtime help and the system manuals listed in the Siemens Industry Online Support portal at support.industry.siemens.com.

1. Problem Statement and Use Cases

Operator audit trails on machine HMIs typically require three pieces of runtime data from the HMI:

• Current user name (string, 24 characters maximum in WinCC Flexible user administration)
• Login state (boolean: 1 = authenticated, 0 = not authenticated)
• Privilege level or group membership (numeric 0 to 9, derived from the user record's group number)

The reference script posted in the field report uses a scheduler-triggered VBScript that reads the runtime user with GetUserName, conditionally calls Logon to enforce a baseline authentication, and writes a single status bit back to the controller. That pattern is a viable starting point but contains a logic inversion and a tag-path issue that the rest of this article resolves. Engineers should use this guide to:

1. Configure a complete HMI-to-PLC tag set covering both string and boolean state.
2. Bind a scheduler task to the User change event so the script runs only when needed.
3. Resolve the "LOGIN_NotLoggedIn" compile error caused by an unresolved tag reference.
4. Implement the minimal one-bit pattern for controllers with no spare string-capable data blocks.
5. Validate the result with a hands-on test procedure that exercises the login, logout, and default-user transitions.

2. System Architecture

The HMI panel is the authentication authority. WinCC Flexible stores user names, passwords, group numbers (0 = no rights, 1 to 9 = increasing privilege), and logoff timeouts in a local encrypted file on the panel. The PLC does not store user data; it only receives a snapshot of the active state through standard cyclic tag polling.

The PLC receives the data through an area pointer configured in the connection table. For a 24-character username on an S7-300/400, allocate a contiguous block of 12 words (each word holds two ASCII characters in S7 string-by-char convention) or 24 bytes when using S7-1200/1500 with the String data type. A single bit for the boolean status requires one M-bit or one DBX bit.

3. Prerequisites

Before writing any code, confirm the following:

• Software: WinCC Flexible 2008 SP3 (or matching version of 2005/2007) installed with the ES (engineering station) license. The PC Runtime is acceptable for bench testing.
• Panel image: A compatible panel image for the target device (TP177, TP277, MP377, etc.) must be installed via the ProSave tool or directly through WinCC Flexible.
• PLC connection: A configured MPI/Profibus/TCP connection in the WinCC Flexible project. For S7-1200/1500 over Ethernet, enable Permit access with PUT/GET on the controller (TIA Portal: Properties > Protection).
• User administration enabled: In the project, open the runtime settings and confirm User administration is active. Without this, GetUserName returns an empty string and the script will perpetually trigger the default-login branch.
• A test PLC tag block: A DB or Merker area large enough to host a 24-byte string plus a byte for status bits.

4. HMI Tag and User Administration Configuration

Open the project, then complete the tag setup before writing the script. The script cannot compile unless the tags it references exist in the project dictionary.

Create a user administration group with at least three records so the script can be tested against empty, default, and authenticated states:

The NoUser record is the placeholder user the script will log in automatically when no operator is authenticated. Group 0 holds no privileges, so the PLC can safely show machine status without allowing recipe edits.

5. Scheduler Event Configuration

Right-click Schedules in the project tree and add a new task named UserStatusSync. Two event triggers are useful in combination:

1. Event: User change. Located under the system events. Fires every time a login, logoff, or user-switch occurs. This is the primary trigger for the script.
2. Event: 1 s cyclic. Added as a secondary watchdog. It compensates for any missed events and guarantees the PLC state is refreshed after a panel reboot.

For each event, assign the same VBScript function (see section 6). Do not run the script on every value-change of a tag; the user-change event is the correct semantic anchor and avoids unnecessary PLC traffic.

6. VBScript Implementation

The corrected version of the original script addresses three issues: the tag path syntax, the logic inversion of the status bit, and the silent loss of the username string. The full working script is below.

'==========================================================
' File: UserStatusSync.vbs
' Project: WinCC Flexible 2008 SP3
' Trigger: Scheduler -> User change AND 1 s cyclic
'==========================================================
Option Explicit

Dim sUser, sDefaultPwd, sDefaultName, iGroup, sHeartbeat

sDefaultPwd  = "default"           ' Password for the NoUser placeholder
sDefaultName = "NoUser"            ' Username of the placeholder record

' --- Step 1: Read the current operator --------------------
GetUserName sUser

If Len(sUser) = 0 Then
    ' No one is logged in -> force a baseline login so the
    ' panel never operates with an undefined operator.
    Logon sDefaultPwd, sDefaultName
    sUser = sDefaultName
End If

' --- Step 2: Look up group membership ---------------------
iGroup = GetUserGroup(sUser)        ' Returns 0..9

' --- Step 3: Push state to the PLC ------------------------
SmartTags("UserName")             = sUser
SmartTags("UserState_Group")      = iGroup

' Inverted bit: 0 = real user authenticated, 1 = no one
If sUser = sDefaultName Then
    SetBit   SmartTags("UserState_LoggedIn")
Else
    ResetBit SmartTags("UserState_LoggedIn")
End If

' --- Step 4: 1 Hz heartbeat for PLC dead-man detection ----
If SmartTags("UserState_Heartbeat") = 0 Then
    SetBit   SmartTags("UserState_Heartbeat")
Else
    ResetBit SmartTags("UserState_Heartbeat")
End If

Key differences from the original posting:

• SetBit and ResetBit now target the boolean tag UserState_LoggedIn directly, without a System\ prefix that was not present in the project dictionary.
• The status bit is named for the positive condition (LoggedIn) and reset to 0 when a real operator is present, which is the convention used by S7 logic in the rest of the plant.
• The username is written as a string to SmartTags("UserName") so the PLC receives the full identity, not just a flag.
• A heartbeat toggle is added so the PLC can detect a frozen or disconnected HMI within one second.

7. Resolving the LOGIN_NotLoggedIn Compile Error

The original posting reports a compile error on the line SmartTags("System\LOGIN_NotLoggedIn"). The two most likely causes, in order of probability, are:

8. Boolean-Only Status Display (Single-Bit Pattern)

When the PLC has no free string-capable data block and the application only needs a single bit ("is a real operator logged in right now?"), the script collapses to the minimal form below. Place it in a scheduler task triggered by User change; the cyclic trigger is not required for this pattern.

' Single-bit pattern: 1 = real user, 0 = no one / default
Option Explicit
Dim sUser
GetUserName sUser
If Len(sUser) > 0 And sUser <> "NoUser" Then
    ResetBit SmartTags("UserState_LoggedIn")
Else
    SetBit   SmartTags("UserState_LoggedIn")
End If

The PLC logic for a recipe-edit enable line then becomes a single bit test, for example in SCL/ST:

// S7-1500 SCL on DB100.DBX24.0 (UserState_LoggedIn)
IF "DB100".UserState_LoggedIn = FALSE AND "DB100".UserState_Group >= 3 THEN
    bAllowRecipeEdit := TRUE;
ELSE
    bAllowRecipeEdit := FALSE;
END_IF;

To expose the same state to a third-party device that only consumes GSD/EDS-style data, also publish the bit to a Modbus holding register using the Modbus TCP/IP area pointer available in WinCC Flexible 2008 SP1 and later (channel: Modicon Modbus TCP/IP).

9. PLC Program Reference (S7-1200/1500 in TIA Portal)

On the controller side, allocate a global DB to mirror the HMI data block. The block should be marked as non-optimized in TIA Portal so the HMI can access individual bytes and bits by absolute address, or keep it optimized and expose each element with the Accessible from HMI attribute.

// DB100 "HMI_UserStatus"  -  TIA Portal V15.1+
TYPE HMI_UserStatus :
STRUCT
    sUserName        : String[24];   // bytes 0..25 (2 byte header + 24 chars)
    bUserLoggedIn    : Bool;         // byte 26.0
    bUserHeartbeat   : Bool;         // byte 26.1
    iUserGroup       : Int;          // bytes 28..29
END_STRUCT
END_TYPE

DATA_BLOCK "HMI_UserStatus"
{ S7_Optimized_Access := 'FALSE' }
VERSION : 0.1
NON_RETAIN
  STRUCT
     sUserName      : String[24];   // initial := ''
     bUserLoggedIn  : Bool;
     bUserHeartbeat : Bool;
     iUserGroup     : Int;
  END_STRUCT
END_DATA_BLOCK

Add a heartbeat supervision OB (or use the existing cyclic OB1) that raises an HMI-fault bit if the heartbeat toggle does not change for more than 3 s. This is the cheapest way to satisfy the IEC 61131 requirement for fail-safe operator-station detection.

10. Verification Procedure

After the project has been compiled and downloaded to the panel, walk through the following sequence with the panel in Online mode and a tag monitor open in the PLC (online watch table on the DB):

1. Power-cycle the panel. The script should run on the User change event triggered by the initial state. Confirm that sUserName reads 'NoUser' and bUserLoggedIn = TRUE within 2 s of boot.
2. Log in as Operator / op1234 from the panel. The User change event must fire, and within 500 ms the DB must show sUserName = 'Operator', bUserLoggedIn = FALSE, and iUserGroup = 3.
3. Log out. Confirm the system auto-logs in NoUser and the bit returns to TRUE with iUserGroup = 0.
4. Wait 60 s and observe the heartbeat bit toggle. The PLC should see a transition at least once per second.
5. Disconnect the Ethernet cable. Within 3 s, the PLC should raise the HMI-fault bit and disable all recipe-edit operations.

Repeat steps 1 to 5 with the panel in Runtime mode on the engineering PC (WinCC Flexible RT) to confirm the same behavior in both targets. The HMI behavior is identical across physical panels and PC Runtime, but the on-line tag monitor on the PC side is more convenient for capturing transitions.

11. Migration Path to TIA Portal (WinCC V11+)

Projects that started in WinCC Flexible are migrated to TIA Portal with the Migrate project wizard. The tag names, scheduler events, and scripts are carried over, but the API surface changes:

• SmartTags("X") is replaced by SmartTags("X") in VBScript for the unified comfort panel and by HmiRuntime.SmartTags("X") for the WinCC Unified runtime.
• SetBit / ResetBit remain valid for boolean tags.
• GetUserName is replaced by HmiRuntime.ActiveUser.Name in WinCC Unified V16+. See the Siemens Industry Online Support entry support.industry.siemens.com for the function-name mapping table.
• Area pointers are configured per connection, not globally, and require the HMI tags editor to be in Absolute access mode.

The conceptual pattern — scheduler task listening to user change, push state to PLC, single bit for boolean use cases — remains valid and is the recommended approach for new TIA Portal projects as well.

12. Troubleshooting Matrix

FAQ