Safety Integrated - Industry - Siemens

Time sequence
For a better understanding, the time sequence of the parameters
used in the sample project is displayed in this section.
The name of the parameters corresponds to the symbols in
the STEP 7 project.
Variable Input / output Note/Explanation
START Input (NO) Start command for switching
the actuator on.
STOP Input (NC) Stop command for switching
the actuator off.
ACK Input (NO) Acknowledgement signal
OSSD Cyclic input date Bit which reads the fail-safe
S7-CPU of the LS4 via
PROFIBUS. A signal change
from "1" to "0" indicates a detection
zone violation.
ACTUATOR Output fail-safe output with indicator
light connected to it.
START 1
(NO)
0
STOP 1
(NC)
0
ACK 1
(NO)
0
OSSD 1
0
ACTUATOR 1
0
Note
Requirement for the above time sequence is an
adjusted, active zone pair.
Detection zone
violation
An explanation of the times is given in the diagram below:
Time Explanation
t1 Switching the actuator on: Indicator light goes on
(ACTUATOR="1").
t2 Switching the actuator off: Indicator light goes on
(ACTUATOR="0").
t3 Switching the actuator on: Indicator light goes on
(ACTUATOR="1").
t4 LS4 recognizes a violation of the active detection zone
(OSSD="0") . Then...
t5 ...a restart does not cause the indicator light to be switched on,
but...
t6 ...it must first be acknowledged. Only then...
t7 …does a renewed start request cause the indicator light to be
switched on.
t1 t2 t3 t4 t5 t6 t7
Functional Example No. AS-FE-I-010-V11-EN 295
t
t
t
t
t
G_FB_XX_178
Ex. No.
10