
B-6
Ladder Logic (LAD) for S7-300 and S7-400
C79000-G7076-C504-02
Table B-4 Elements of Absolute Programming for Detecting Direction
System Component
Absolute Address
Photo electric barrier 1 I 0.0
Photo electric barrier 2 I 0.1
Display for movement to right Q 4.0
Display for movement to left Q 4.1
Pulse memory bit 1 M 0.0
Pulse memory bit 2 M 0.1
Q 4.1
Photoelectric barrier 1
“PEB1”
S
Display for movement to left
“LEFT”
I 0.0
Network 1: If there is a transition in signal state from 0 to 1 (positive edge) at input I 0.0 and, at the
same time, the signal state at input I 0.1 is 0, then the package on the belt is moving to the left.
Pulse memory bit 1 Photoelectric barrier 2
P
“PMB1” “PEB2”
I 0.1M 0.0
Network 2: If there is a transition in signal state from 0 to 1 (positive edge) at input I 0.1 and, at the
same time, the signal state at input I 0.0 is 0, then the package on the belt is moving to the right. If one
of the photoelectric light barriers is broken, this means that there is a package between the barriers.
Q 4.0
Photoelectric barrier 2
“PEB2”
S
Display for movement to right
“RIGHT”
I 0.1
Pulse memory bit 2 Photoelectric barrier 1
P
“PMB2” “PEB1”
I 0.0M 0.1
Network 3: If neither photoelectric barrier is broken, then there is no package between the barriers.
The direction pointer shuts off.
Q 4.0
Photoelectric barrier 1
“PEB1”
R
Display for movement to right
“RIGHT”
I 0.0
Photoelectric barrier 2
“PEB2”
I 0.1
Display for movement to left
Q 4.1
R
“LEFT”
Figure B-4 Ladder Logic for Detecting the Direction of a Conveyor Belt
Programming Examples
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