Configuring Siemens SIMATIC VS120 Vision Sensor with S7-300 PLC

Overview of SIMATIC Machine Vision and S7-300 Integration

The SIMATIC Machine Vision family from Siemens bundles industrial-grade image processing into compact, IP67-rated sensors designed for direct integration with SIMATIC controllers. The portfolio spans the entry-level VS110 / VS120 compact sensors and the higher-performance VS72x series (VS721, VS722, VS723, VS724). All members expose a common PROFINET IO / PROFIBUS DP connectivity model, which makes the configuration workflow against a SIMATIC S7-300 CPU nearly identical across the line.

This reference walks through the complete path from a powered sensor on the shop floor to verified cyclic I/O exchange with a SIMATIC S7-300 PLC. Topics covered include hardware configuration in STEP 7 V5.5 and TIA Portal, software installation of Spectation V2.8.2 engineering software and VS Link V1.2.6 configuration software, PROFINET device naming, function-block programming on the S7-300, and the final commissioning checks that confirm cyclic data exchange. The reference cites the official Siemens support entry 16531802 — Tips and Tricks for SIMATIC VS72x for further application examples.

SIMATIC VS Sensor Family Comparison

The following table summarizes the differentiating parameters of the SIMATIC VS line as deployed with an S7-300. Values are taken from the respective Siemens operating instructions and the VS72x tips & tricks entry. Where a row is not applicable to a model, the cell is marked “n/a”.

All VS variants present themselves on PROFINET as a modular I/O device. The default module layout is 4 bytes input / 4 bytes output (control word + status word + 16-bit result), expandable up to 32 bytes in each direction when extended result / command channels are activated in Spectation.

Prerequisites: Hardware, Software, Cabling

Confirm the following before powering the sensor. Skipping any item typically surfaces as cryptic PROFINET alarms (see troubleshooting matrix below).

The S7-300 system is documented at SIMATIC S7-300 product page; PROFINET conformance is per IEC 61158 / IEC 61784, which the VS sensors implement through the standard PROFINET IO Device stack.

Installing Spectation V2.8.2 and VS Link V1.2.6

1. Install Spectation V2.8.2 first. It contains the offline job editor, image catalog, and the OPC-style script runtime used inside the sensor.
2. Accept the default installation directory (typically C:\Program Files\Siemens\Spectation). The installer registers a service that exposes the local image database to VS Link.
3. Install VS Link V1.2.6. VS Link is the network configuration utility — it discovers the VS sensors on the service subnet, pushes the device name, sets the PROFINET device name, and uploads / downloads the compiled job (Spectation output).
4. Start VS Link. The first run prompts for a project directory. Create one per cell, e.g. D:\VS_Projects\Cell_A.
5. Connect the service PC to the VS sensor using either RS-232 (VS7xx) at 115 200 / 8 / N / 1 or Ethernet (VS110/VS120). On the VS110/120 the default service IP is 192.168.1.100 / 24.

PROFINET Hardware Configuration in STEP 7 V5.5 / TIA Portal

The S7-300 project must contain the VS sensor as a PROFINET IO device. The procedure differs slightly between the two engineering tools but produces the same PROFINET configuration on the wire.

STEP 7 V5.5 (HW Config)

1. Open the S7 project in STEP 7 V5.5 and launch HW Config.
2. Open the Options > Install GSD File dialog and select the VS GSDML file. After successful install the VS device appears under PROFINET IO > Additional Field Devices > Sensors > Siemens AG > SIMATIC VS.
3. Drag the VS sensor onto the PROFINET IO system assigned to the S7-300 CPU. The default PROFINET device name assigned by HW Config is vs72x-1; rename it to match the VS Link project (e.g. cell-a-vs-1).
4. Assign the VS sensor to the same PROFINET IO subnet as the CPU. STEP 7 proposes an IP address in the same subnet as the CPU interface; keep the proposal or enter one consistent with the cell IP plan.
5. Insert the 4 Byte DI / 4 Byte DO module (or the wider module matching the Spectation job) into slot 0 of the VS device. STEP 7 assigns I-address and Q-address ranges in the S7-300 process image — note them for the PLC program.

TIA Portal (Devices & Networks)

1. Open the project in TIA Portal and switch to Devices & Networks.
2. Options > Manage general station description files (GSD) — install the VS GSDML.
3. Drag the VS device from the hardware catalog onto the PROFINET subnet. TIA Portal generates a default device name, IP, and module slot.
4. Open the VS device properties and align the I/O addresses to the desired ranges in the S7-300 process image (e.g. IB 100 – IB 103 / QB 100 – QB 103).
5. Compile the S7-300 station and download HW Config to the CPU.

PROFINET Network Commissioning and Device Naming

1. In VS Link, click Search for Devices. The tool broadcasts a DCP identify-all and lists every VS sensor on the service subnet with its MAC, current IP, current PROFINET name, and serial number.
2. Select the sensor whose serial number matches the label on the housing. Click Assign Name and enter the same name used in HW Config / TIA Portal (e.g. cell-a-vs-1). Confirm with Assign IP, entering the IP that matches HW Config.
3. Restart the sensor (power cycle) so the new name takes effect. The PROFINET LED transitions from flashing to steady once the controller establishes an AR (Application Relationship).
4. Return to STEP 7 / TIA Portal and confirm the VS device shows No fault in the online diagnostics view. The cyclic I/O LEDs on the CPU blink at the configured update rate (default 1 ms).

If the sensor does not appear in the search, the most common cause is a managed switch filtering LLDP / DCP multicast. Either enable PROFINET filter per the switch vendor doc, or temporarily connect the service PC directly to the sensor port.

Programming the VS Sensor Application in Spectation

1. Launch Spectation and create a new project. The Spectation script editor is a sequential, line-by-line environment — each line of the job produces one evaluation per trigger.
2. Define the trigger: either PROFINET control word bit (rising edge on bit 0 of the output) or the hardware trigger input on the sensor's M12 connector. For a PLC-driven cell, PROFINET triggering is the default.
3. Add evaluation blocks. Common blocks for an S7-300 cell are: Pattern Match, Brightness, Edge Count, Position, Blob, and Read Code (1D / 2D where licensed).
4. Map the boolean result of each block to one of the 16 available result bits in the status word. The S7-300 typically reads the result bits from input bytes 2 and 3 of the VS PROFINET slot.
5. Compile the job to the sensor via VS Link. The compiled binary is stored in non-volatile memory on the sensor; the active job number is selectable through the PROFINET control word.

S7-300 PLC Program Integration

The S7-300 reads the VS status word and writes the VS control word. The minimum useful exchange is one FC that performs three functions: trigger the inspection, wait for the result-ready bit, and read the result bits. The example below uses the default 4-byte I/O at addresses PIW 100 / PQW 100.

Symbol Table

FC100 — VS120 Trigger and Read (STL)

FUNCTION FC 100 : VOID
VAR
    busy        : BOOL;     // bit 0 of VS_Status, mirrored
    ready       : BOOL;     // bit 1 of VS_Status, mirrored
    error       : BOOL;     // bit 2 of VS_Status, mirrored
    result_bits : WORD;     // concatenated result bits 0..15
    trig        : BOOL;     // rising-edge trigger from line PLC
END_VAR
BEGIN
    NETWORK 1 // Mirror status bits
        A   I 100.0;     =   #busy;
        A   I 100.1;     =   #ready;
        A   I 100.2;     =   #error;

    NETWORK 2 // Read result word
        L   IB 102;
        T   LW 0;        // temp
        L   IB 103;
        T   LW 1;        // temp
        L   LW 0;
        SLD 8;
        OW;
        T   #result_bits;

    NETWORK 3 // Edge-triggered inspection
        A   #trig;
        FP  M 50.0;       // trigger one-shot
        JCN _NO_TRIG;
        L   #VS_Job;      // current job (0..255)
        SLD 4;            // align to bits 4..11 of control word
        OW  W#16#0001;    // set trigger bit
        T   QW 100;
        AN  #busy;
        JC  _NO_TRIG;     // sensor still busy, skip
_NO_TRIG: NOP 0;

    NETWORK 4 // Clear trigger once sensor acknowledges busy
        A   #busy;
        R   Q 100.0;
END_FUNCTION

FC101 — Job Switch

FUNCTION FC 101 : VOID
VAR_INPUT
    new_job : INT;        // 0..255
END_VAR
BEGIN
    NETWORK 1 // Validate range
        L   #new_job;
        L   255;
        >I;
        JC  _ERR;
        L   0;
        <I;
        JC  _ERR;

    NETWORK 2 // Write job into control word bits 4..11
        L   #new_job;
        SLD 4;
        T   QW 102;
        BEA;
_ERR:  S   M 60.0;        // job range flag
END_FUNCTION

For TIA Portal projects, the same logic is implemented in an FB written in SCL or LAD; the I/O addressing is via the HW tag table rather than absolute PIW/PQW.

Verification, Diagnostics, and Acceptance Test

1. Place a known-good part in the sensor field of view.
2. Force the trigger input in STEP 7 / TIA Portal (e.g. set M 50.0 true). Confirm that VS_Status bit 0 transitions to 1 within one PROFINET update cycle.
3. Verify bit 1 (result ready) transitions to 1 within the configured inspection time (typically < 50 ms for a single block, < 200 ms for a 5-block job).
4. Read VS_ResultLo and confirm the expected result bit is set (e.g. result bit 0 = pattern match OK).
5. Place a known-bad part; verify the corresponding result bit clears and the global error bit (status bit 2) is set if Spectation is configured to assert it on negative results.
6. Capture the online PROFINET diagnostics in HW Config / Devices & Networks. The VS device must show No fault, with the cyclic I/O indicators blinking at the configured update rate.
7. Run a 1 000-trigger soak test in Spectation to confirm the inspection time stays below the line cycle time.

Troubleshooting Matrix

For a deeper catalog of pitfalls (lens selection, illumination mounting, line-scan exposure timing) the Siemens Tips and Tricks for SIMATIC VS72x entry is the canonical reference. For cross-vendor comparison and selection criteria outside the Siemens portfolio, see Keyence vision sensors for a representative compact-sensor offering.

Field-Proven Notes and Best Practices

• Keep the 24 V supply to the VS sensor on a separate branch from any VFD or contactor coil. The sensor's PROFINET port is not isolated against common-mode transients on the power input.
• For reflective parts, mount the illumination at 15°–25° off-axis; for matte parts, use coaxial or ring light at near-normal incidence.
• Set the PROFINET send clock to 1 ms, but configure the reduction ratio so the VS sensor is polled at 4 ms (4× reduction). This is the proven balance between S7-300 CPU load and inspection latency.
• Always store the active Spectation project and the compiled job binary in the same S7 project folder as the STEP 7 source. This keeps the configuration reproducible across controller swaps.
• Document the PROFINET device name, IP address, and active job number in the HMI screen, not just in the PLC program. A field engineer replacing a sensor head must be able to identify all three from the HMI.