Basic PLC Ladder Programming Example 14

Basic PLC
Ladder Programming Training Example 14 : 24 Hour clock using Counter PLC Ladder Program 

Basic PLC Ladder Programming Training Examples for Beginners. Hi
Friends here we are starting a series of Free Training on PLC Ladder
Programming. These PLC Ladder Programs are important to get basics of Ladder

PLC Ladder
Practice Problem:

  •  Using 3 counters together with the flag of M1013 (1s clock pulse) to
    operate a 24-hour clock. 

Covered in this example is use of
Counter in PLC Program  
Number of
PLC Counter Required 

C0 – count per second
C1- count per minute
C2 – count per hour 
Number of
PLC internal memory flag Required

M1013 – 1s clock 

PLC Ladder

PLC Ladder
Programming Description: 


  • The key of operating a 24-hour clock is to use M1013 (1s clock
    pulse). When the program is executed, C0 will count once per second. When the
    counted number reaches 60(1 minute), C0 = ON. C1 will count once, and C0 will
    be reset at the same time; similarly, when the counted number in C1 reaches
    60(1 hour), C1 = ON. C2 will count once, and C1 will be reset at the same time.
    Furthermore, when the present value in C2 reaches 24, C2 will be reset, and the
    24-hour counting process will start again.
  • The 24-hour clock operates by using C0 to count “second”, C1 to
    count “minute” and C2 to count “hour.” In this clock, the value of “second”,
    “minute” and “hour” can be read by C0, C1 and C2 correspondingly. When the set
    value of C2 is 12, the clock will be a 12-hour clock.  

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