Rockwell Automation Publication 1756-AT017A-EN-P - January 2013
Position-based Output Control with the MAOC Instruction 13
Strobe Trigger Example
In this strobe trigger example, a camera takes a picture of labels on boxes as they
travel along a conveyor. The conveyor can be driven by any device, such as a servo
drive, variable frequency drive, or soft starter. An encoder sends the speed of the
conveyor to the controller.
Figure 11 - Strobe Trigger Example
The programming logic for this example must take into account the following:
• Boxes on the conveyor are 1000 mm apart.
• The strobe must trigger when a box is in the middle of its travel, nominally
at 500 mm.
• The duration of the strobe light flash must be exactly 10 ms.
• To account for boxes that are out of place, the strobe must trigger multiple
times: just before, at, and just after the center of the field of view.
Figure 12 shows the configuration of the output cam for this example. As the axis
travels through the 450 mm, 500 mm, and 550 mm points, the strobe output
turns On for 10 ms, independent of the scan time of the controller. This is
especially useful for applications with long scan times, or exact requirements for
the On time duration.
Figure 12 - Output Cam for Strobe Trigger
Encoder
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