The IEC 61131 standart offers a definition of Timers. PLC3000 integrates only TON timers that can be set by defining the time base %Ti.TB, and the preset value %Ti.PV. The timer is triggered by activating the input %Ti.IN, and the output %Ti.Q goes to 1 when the current timer value reaches the preset value.
The time bases %Ti.TB that can be declared are: 1, 10, 100 ms; 1, 10 s; 1 min.
Generation in LD
A Timer, its preset value and time base are defined during the variable creation with the Ladder code editor. For example, the Timer %T0 with a preset value %T0.PV=5 and a time base 100ms is defined as:
Illustration with a Grafcet
Let’s considering the following Grafcet
Programming in LD – Step/Step with Crossing Bits