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Example 6: Sequence control
If the N.C. contact of Y2 in the interlocking control configuration of example 5 is put in
series with the Y1 circuit, so that it is an AND condition for actuation of Y1 (see figure below),
not only is Y1 a condition for the actuation of Y2 in this circuit, the actuation of Y2 will also
stop the actuation of Y1. This configuration confirms the actuation order of Y1 and Y2.
Example 7: Oscillating circuit
Oscillating circuit with a period of ΔT+ΔT
The figure below shows a very simple ladder diagram. When starting to scan the Y1 N.C.
contact, because the Y1 coil has lost power, the Y1 N.C. contact will be closed. When the Y1
coil is then scanned, it will be electrified, and the output will be 1. When the Y1 N.C. contact
is scanned in the scanning cycle, because Y1 coil is electrified, the Y1 N.C. contact will be
open, the Y1 coil will then lose power, and the output will be 0. Following repeated scanning,
the output of Y1 coil will have an oscillating waveform with a period of ΔT (On) +ΔT (Off).
Y1
Oscillating circuit with a period of nT+ΔT
The program of the ladder diagram shown below uses timer T0 to control coil Y1's
electrified time. After Y1 is electrified, it causes timer T0 to close during the next scanning
cycle, which will cause the output from Y1 to have the oscillating waveform shown in the
figure below. Here n is the timer's decimal setting value, and T is the clock cycle of the timer.
X0
T0
X1
Y1
X2
Y2
Y1
Y1
T0
Kn
TMR
Y1
16-23
Chapter 16 PLC Function Applications│CFP2000
X3
Y2
Y1
X4
Y1
Y2
Y1
T
T
X0
Y1
nT
T
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