Delta MH300 Series - Page 886

Chapter 16 PLC Function ApplicationsMH300
16-23
compiling program may sometimes omit identical state output, as shown in Figure 16-36.
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MPS
MPP
MRD
Figure 16-36
16-4-4 Common basic program design examples
Start, stop, and protection circuits
Some applications may require a brief close or brief break using a button to start and stop equipment.
A protective circuit must therefore be designed to maintain continued operation in these situations.
This protective circuit may employ one of the following methods.
Example 1: Priority stop protective circuit
When the start N.O. contact X1=ON, and the stop N.C. contact X2=OFF, Y1=ON. If X2
switches to ON, coil Y1 is no longer electrified, and this is therefore referred to as priority
stop. See Figure 16-37.
Y1
X2
X1
START
STOP
Y1
Figure 16-37
Example 2: Priority start protective circuit
When the start N.O. contact X1=ON, and the stop N.C. contact X2＝
OFF, Y1=ON, and
coil Y1 is electrified and protected. If X2 switches to ON, coil Y1 still protects the contact
and continues to be electrified, and this is therefore referred to as priority start. See Figure
16-38.
Y1
X2
X1
START
STOP
Y1
Figure 16-38