Image Trigger Station

In some applications, the image acquisition must be triggered directly on the camera by an external trigger, e.g. when components pass in front of the camera on a conveyor belt.

A handshake as with Vision standard station would possibly be too slow here. With Image Trigger Station the evaluation is therefore started by the image acquisition itself.

This requires a different handshake:

../../_images/Timing_VisionStationImageTrigger.png

Procedure

  1. The station sets READY to HIGH after loading the VisionJob.

  2. The PLC sets ENABLE to prepare the station.

  3. After the station has configured the image source, WAITING signals that the station is waiting for the next image acquisition.

  4. From now on, the PLC can trigger the image acquisition of the camera via hardware trigger.

  5. After the image transmission, the station starts the evaluation. During the evaluation are:

    • BUSY: HIGH

    • IO: LOW

    • NIO: LOW

    • ERROR: HIGH

  6. At the end of the evaluation BUSY is set to LOW and one of the result bits is set to HIGH:

    • IO: Good Part

    • NIO: Bad Part

    • ERROR: Error during evaluation

  7. The two bits FINISHED_1 and FINISHED_2 change their state after each image evaluation. The PLC can determine by the edge change whether an evaluation has taken place.

Hint

After restart or reset of the BV, both finished bits are set to LOW. This allows the PLC to distinguish between a real evaluation (1 bit HIGH, 1 bit LOW) and a reset (both bits LOW).

Configuration

Like any station, the Image Trigger Station is configured in stations.xml:

<station id="1" name="BV 1"  type="VisionStationImageTrigger">
  <param name="timeoutAllImages" value="10000"/>
  <param name="resetOutDataOnStart" value="False"/>
  <handshake>
    <param name="bitToASCII" value="false"/>
    <in>
      <bit bitRef="1001" id="enable"/>
    </in>
    <out>
      <bit bitRef="1001" id="ready"/>
      <bit bitRef="1002" id="busy"/>
      <bit bitRef="1003" id="error"/>
      <bit bitRef="1004" id="io"/>
      <bit bitRef="1005" id="nio"/>
      <bit bitRef="1006" id="waiting"/>
      <bit bitRef="1007" id="finished0"/>
      <bit bitRef="1008" id="finished1"/>
    </out>
  </handshake>
  <commandInterface>
    <in>
      <data dataRef="07" offset="0" length="24" id="DATA"/>
    </in>
    <out>
    </out>
  </commandInterface>
</station>

Parameters

  • timeoutAllImage: After the first image, all further images must be received within this timeout. Only active if multiple jobs are assigned to the station.

  • resetOutDataOnStart: If True, all output variables of the executed ToolGroupItems are set to their default values in addition to the handshake bits.

  • setBusyWithData: See Vision standard station

In addition, Criteria bits and user bits can also be used.

Note

The Image Trigger Station can currently only be used for BV jobs with exactly one physical image source, which can however provide multiple images as a master-slave-image-source.

Hint

If WAITING does not change to HIGH, the cause must be checked via the log file.

See also
Vision standard station
GInOut