Configuring External Operator Bells and Horn Signal Modules in SIMATIC PCS 7 WinCC

In SIMATIC PCS 7 WinCC, external audible annunciators—such as high-decibel control room bells, horns, and sirens—are configured using the WinCC Horn editor. When client workstation sound cards are unavailable or industrial 24V DC / 230V AC signals are required, engineers configure physical outputs via PCI/PCIe signal modules (using driver HMPCI64.INF) or route Horn message-class trigger tags across the plant bus to Automation Station digital output channels driving physical relays.

Audible Annunciation Architecture in SIMATIC PCS 7 WinCC

Industrial control rooms require immediate acoustic notification when high-priority process alarms (such as safety trips, environmental deviations, or critical interlocks) occur. In SIMATIC PCS 7, this functionality is provided by the Horn component of WinCC:
* Audio Card Annunciation: Plays customized .wav audio files through workstation speakers or external sound systems based on alarm priority.
* Signal Module Annunciation: Triggers hardware relay contacts on dedicated PCI or PCIe signal plug-in cards installed directly in the OS client or OS single station IPC.
* AS Process Bus Routing: Sets a binary tag in WinCC upon active unacknowledged alarm, transmitting a signal to an Automation Station (AS) digital output channel that energizes an industrial bell or rotating beacon.

Configuring the WinCC Horn Editor for Sound and Signal Routing

To configure acoustic alarms in WinCC Explorer:
1. In the WinCC project tree, right-click Horn and select Open.
2. Message Assignment Tab:
* Define filtering criteria based on message classes (e.g., Alarm High, Warning High, Process Message).
* Assign authorization levels and area filtering so operators only hear alarms for their designated plant sections.
* Map the filtered message class to a logical Signal Tag (e.g., Horn_Alarm_Active).
3. Signal Assignment Tab:
* Link the logical Signal Tag to a physical output.
* For sound cards, specify the exact .wav file path.
* For hardware signal cards, select Output 1, Output 2, or Output 3.
* For PLC relay activation, assign an internal or external binary process tag.
4. Set the acknowledgment behavior: configure whether the signal silences when the operator clicks the Horn Silence button in the OS runtime header, or whether silencing requires full alarm acknowledgment.

Hardware Implementation: PCI/PCIe Signal Modules

When using industrial signal cards (such as the Siemens 6DS1916-8RR PCI card or modern PCIe equivalents):
1. Install the card into an available PCI/PCIe slot of the OS workstation IPC.
2. In Windows Device Manager, locate the card under Other devices (often identified as a system controller).
3. Right-click and choose Update driver software, navigating to Siemens/WinCC/Options/Drivers/ and selecting HMPCI64.INF.
4. Once installed, open Control Panel -> Signal Unit Hardware Setup to configure relay pulse duration and test hardware contacts.
5. Connect external 24V DC bell circuits to the isolated relay contact terminals on the card connector.

Software Implementation: AS Digital Output Relay Trigger via PLC Tags

In modern distributed architectures where OS clients lack PCI expansion slots, routing via the Automation Station is the standard engineering practice:
1. Create WinCC Binary Tag: In WinCC Tag Management, create an external binary tag Bell_Trigger mapped to a CFC input pin or DB bit on the process bus connection.
2. Assign in Horn Editor: In the Horn editor's Message Assignment tab, configure the target alarm classes to energize Bell_Trigger.
3. CFC Logic in AS:
* In a CFC chart executing in cyclic interrupt OB35, feed Bell_Trigger into a pulse timer block (e.g., TIMER_P or standard APL logic).
* Connect the timer output to the channel driver block (Pcs7DiOu) addressing an ET 200 digital output module.
* Connect the digital output to an interposing 24V DC relay powering the plant bell or siren.
4. Silencing Logic: Route the standard WinCC horn silence event (@HornReset) to reset the trigger tag, allowing operators to silence the bell immediately from any OS client station.

Verification

In CFC or runtime simulation, trigger a high-priority process alarm.
Confirm that the designated digital output channel on the ET 200 rack energizes and the external bell sounds.
Click the Acknowledge Horn button in the WinCC runtime banner: verify that the bell silences immediately while the visual alarm remains flashing until acknowledged.
Check the WinCC alarm log to ensure the message was correctly categorized under the assigned horn message class.

Limitations and Operational Precautions

Ensure high-decibel bells are driven through interposing relays; never connect high-inductance electromechanical bells directly to sensitive solid-state PLC output cards without flyback diode or snubber protection.
If multiple OS clients share a single external bell via the AS, ensure horn acknowledge logic on any client silences the common bell to prevent operator fatigue.
Signal module PCI cards require compatible 64-bit drivers (HMPCI64.INF); verify driver compatibility when migrating Windows operating systems.

Engineer FAQ

Can I use both PC sound card audio and an external bell simultaneously?
Yes, the WinCC Horn editor allows simultaneous assignment of .wav sound files and external binary signal tags to the same alarm class.
What is the difference between acknowledging the horn and acknowledging the alarm?
Acknowledging the horn silences the audible sound or de-energizes the bell; acknowledging the alarm confirms visual awareness and transitions the alarm from flashing to steady state.
Where is the driver for the Siemens PCI signal module located?
The driver is located on the WinCC installation media and hard drive under <WinCC Installation Directory>/Options/Drivers/HMPCI64.INF.
Can an external bell be triggered only for specific plant areas?
Yes, the Message Assignment tab in the Horn editor supports filtering by both message class and plant area (technological hierarchy).
Why does the external bell stay on continuously after an alarm clears?
If the Horn configuration lacks an automatic reset or pulse duration limit, the tag remains high until an explicit operator silence command resets the signal.
Can I trigger an external bell from a WinCC Web Navigator client?
Web Navigator clients cannot directly trigger physical server signal cards, but server-side Horn instances process alarms and trigger AS outputs regardless of client connection type.
What S7 block is recommended for pulse-stretching the bell trigger in CFC?
The TimerP or PulseGen block is commonly used to ensure the bell rings for a defined minimum duration (e.g., 5 seconds) even if the alarm is fleeting.
Does WinCC OS Redundancy require Horn configuration on both servers?
Yes, in redundant OS server pairs, the Horn editor must be configured identically on both servers, or configured on the clients if sound is localized to client PCs.
Can I use an OPC tag to trigger the external bell?
Yes, any valid WinCC external tag—including OPC DA or OPC UA tags—can be selected as the target signal tag in the Horn editor.
How do I prevent nuisance bell ringing during plant startup?
Use the PCS 7 alarm hiding (smart alarm management) function or operating mode suppression to suppress audible horn generation for uncommissioned units.

Technical References

SIMATIC HMI WinCC V7.5 / V8.0 Horn Configuration Manual
SIMATIC PCS 7 OS Process Control System Operating Manual
Siemens Industry Online Support Entry: External Horn and Signal Modules in PCS 7 (Entry ID 298433)
SIMATIC PCS 7 Advanced Process Library (APL) Function Manual

Related Tags

PCS 7, WinCC, Horn, Audible Alarm, External Bell, Signal Module, HMPCI64, Alarm Logging, ET 200, Relays

Configuring External Operator Bells and Horn Signal Modules in SIMATIC PCS 7 WinCC