Automating Manufacturing Systems - Process Control and ...

plc states - 12.11
FIRST STATE WAIT FOR TRANSITIONS
state_1
MCR
S1
S1
L1
L2
MCR
U
L
Figure 12.12
Ladder Logic for First State
The second state is more complex because it involves a time delay, as shown in
Figure 12.13. When the state is active the TON timer will be timing. When the timer is
done state 2 will be unlatched, and state 3 will be latched on. The timer is nonretentive, so
if state_2 if off the MCR block will force all of the outputs off, including the timer, causing
it to reset.
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