AutomationDirect DL105, Руководство пользователя

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RLL
P
LUS
Stage
Programming
7--14
RLL
PLUS
Stage Programming
DL105 PLC User Manual, 3rd Edition
Some garage door openers today will
detect an object under the door. This halts
further lowering of the door. Usually
implemented with a photocell
(“electric-eye”), a door in the process of
being lowered will halt and begin raising.
We will define our safety feature to work in
this way, adding the input from the
photocell to the block diagram as shown to
the right. X3 will be on if an object is in the
path of the door.
Next, we make a simple addition to the
state transition diagram, shown in shaded
areas in the figure below. Note the new
transition path at the top of the LOWER
state. If we are lowering the door and
detect an obstruction (X3), we then jump
to the Push-UP State. We do this instead
of jumping directly to the RAISE state, to
give the Lower output Y2 one scan to turn
off, before the Raise output Y1 energizes.
Ladder
Program
Inputs Outputs
Toggle
X0 Y1
Raise
Y2
Lower
Up limit
X1
Down limit
X2 Y3
Light
Obstruction
X3
X0
Push--UP
UP
Push--DOWN
DOWN
X0
LOWER
RAISE
X0
X1
X0
X2 and
LIGHT
X0
X0
T0
X3
X3
It is theoretically possible that the down limit (X2) and the obstruction input (X3)
could energize at the same moment. In that case, we would “jump” to the Push-UP
and DOWN states simultaneously, which does not make sense.
Instead, we give priority to the obstruction
by changing the transition condition to the
DOWN state to [X2 AND NOT X3]. This
ensures the obstruction event has the
priority. The modifications we must make
to the LOWER stage (S5) logic are shown
to the right. The first rung remains
unchanged. The second and third rungs
implement the transitions we need. Note
the opposite relay contact usage for X3,
which ensures the stage will execute only
one of the JMP instructions.
OUT
Y2
SP1
S0 X2
JMP
SG
S5
LOWER State
X3
S2 X3
JMP
to Push-UP
to DOWN
Add Emergency
Stop Feature
Exclusive
Transitions