Basic PLC Ladder Programming Examples 23

Basic PLC Ladder Programming Examples 23

Basic PLC Ladder Programming Training Examples for Beginners.  Hi friends, here we are starting unique a series of Free Training on PLC Ladder Programming & tutorials. These PLC Ladder Programs are important to learn basics of Ladder programs.

Example 7: Sequential control

If we serially connect the
normally closed contact of Y2 in example 5 to the circuit of Y1 as an AND
condition for Y1 (as the diagram in the left hand side), the circuit can not
only make Y1 as the condition for Y2, but also allow the stop of Y1 after Y2 is
enabled. Therefore, we can make Y1 and Y2 execute exactly the sequential
control

Example 8: Oscillating circuit

The ladder diagram above is a
very simple one. When the program starts to scan the normally closed contact
Y1, Y1 will be closed because coil Y1 is Off. When the program then scan to
coil Y1 and make it On, the output will be 1. When the program scans to the
normally closed contact Y1 again in the next scan cycle, because coil Y1 is On,
Y1 will be open and make coil Y1 Off and output 0. The repeated scans will
result in coil Y1 outputs oscillating pulses by the cycle

Example 9: Flashing circuit

The ladder diagram is an
oscillating circuit which makes the indicator flash or enables the buzzer
alarms. It uses two timer to control the On/Off time of coil Y1. n1 and n2
refer to the set values in T1 and T2 and T is the cycle of the clock

Example 10: Trigger circuit


The rising-edge differential
instruction of X0 makes coil M0 generate a single pulse of ΔT (one scan cycle).
Coil Y1 will be On during this scan period. In the next scan period, coil M0
will be Off and the normally closed contact M0 and Y1 will all be closed,
making coil Y1 continue to be On until another rising-edge arrives in input X0,
making coil M0 On for another scan period and Y1 Off. Such kind of circuit
relies on an input to make two actions execute interchangeably. Also from the
timing diagram on the last page, we can see that input X0 are square pulse
signals of the cycle T and coil Y1 output are square pulse signals of the cycle
2T.
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