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Functional principle of the joker² light barrier system
Copyright eltima electronic 2022
The curtain barrier with two or three beams
Symbols:
or
, level:
To increase the detection rate, a curtain barrier can be used. In this mode,
the system effectively scans an area formed by two or three light beams. The
light barriers are linked by a logical
OR. This means that the action
mode is met, any one of the light
barriers is interrupted.
Usually the participating light barri-
ers would be set up parallel in a
plane (to make the position of the
subject more predictable), but they
could be set up facing any direction.
In this mode, any beam that is inter-
rupted must be reset before a new
action can be triggered even by a
different beam.
Note: Depending on the application, it can be advantageous to set up
the light barriers vertically, as in the example in Figure 15. In this case
the wide wingspan of the bird allows the beams to be placed farther
apart, increasing the area of detection (blue rectangle). In the hori-
zontal arrangement the birds present a narrower target, so the beams
must be closer together and the active area is much smaller.
The three beam cross barrier
Symbol:
, Level:
Just like the simple cross barrier, the three beams
barrier increases the selectivity of the system.
The light barriers are linked by a logically AND.
The action mode is met when all three light bar-
riers are interrupted at the same time, at which
point the trigger will be passed on to the digital
part.
The light barriers do not need to cross in one
point.
For example in the setup in Figure 16, the large
animal is detected, because it interrupts all three
light barriers, but the small is not because it could
only interrupt at most one barrier.
Once the action is met, all three beams must be
reset before a new action can be triggered.
Figure 15: Curtain barrier
Figure 16: Blanking out of
small objects