Basic PLC Ladder Programming Examples 3


Basic PLC
Ladder Programming Training Examples for Beginners.

friends here we are starting here a series of Free Training on PLC
Ladder Programming training & tutorials.These PLC Ladder Programs
are important to get basics of Ladder programs.

Ladder Practice Problem:

Controlling the running state of the 1 ph motor by pressing START and
STOP pushbuttons i.e. motor should remain in ON state after START pushbutton is
pressed and should OFF when STOP pushbutton is pressed. Checking if the Motor
is running normally by pressing TEST pushbutton.

PLC Ladder Programming Practice Problem 3

Topics Covered in this example is Latching Contacts Ladder Program.

of PLC Inputs Required

X0 – START pushbutton to Start Motor
X1 – STOP pushbutton to Stop Motor
X2 – Error signal from Motor to PLC.

  Number of PLC Outputs Required


Y0 –1 phase Motor

PLC Ladder Programming:

PLC Ladder Programming Practice Problem3

PLC Ladder Program

  1. Press START button lightly and X0 = ON. The Motor will keep running if
    no error occurred (X3 = OFF). The action can be practiced by a latching circuit
    which takes output Y0 as one of the input condition to keep the motor running
    even if the START button is not pressed(See
    normally open contact Y0 below X0
  2. When STOP button is pressed, X1 = ON and Y0 = OFF. The motor will stop
  3. If error occur (X3 = ON), Y1 will be OFF and the motor will stop
  4. When TEST is pressed (X2 = ON), Y0 = ON. The motor will start running if
    no error occurred (X3 = OFF). On the contrary, when TEST is released, the motor
    will stop running. The testing function is performed by this process.    

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