The counter Z4 is set to a value of 10 corresponding with closure of input E1.3. It then counts backwards each time input E1.2 is closed. The output A2.7 is deactivated at the end of the countdown (value 0).

The ladder program is very simple. Assigning the constant KZ10 to input ZW simplifies setting the value of the counter to 10. The set input (S) has been connected to a contact E1.3 whereas the decrease (ZR) connects to a contact of E1.2. On the rising edge of E1.3 the value of the counter is programmed to 10. Each rising edge of E1.2 reduces the count by 1 unit. The output from the counter (Q) is high when the value of the count is not equal to 0. Therefore all that is required is to use it to control output A2.7 of the PLC.

The first group of statements of the AWL program increases the value of the counter Z4 by 1 unit on each rising edge of E1.2. The second group programs the counter with the values stored in ACCU1 (10) corresponding with the rising edge of E1.3. The last group transfers the status of the counter to output A2.7.

More examples: [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ] [ 10 ] [ 11 ] [ 12 ] [ 13 ] [ 14 ] [ 15 ] [ 16 ] [ 17 ] [ 18 ] [ 19 ] [ 20 ] [ 21 ] [ 22 ] [ 23 ] [ 24 ] [ 25 ] [ 26 ] [ 27 ] [ 28 ] [ 29 ] [ List ]
More PLCs examples: Not still available