Author Topic: Difference between level and trigger?  (Read 8735 times)


  • Guest
Difference between level and trigger?
« on: May 17, 2010, 10:38:02 AM »
What is the difference between level and trigger in the activation of coils?


  • Developer
  • Administrator
  • *****
  • Posts: 924
  • Nirtec
    • The EasyPLC Project
Re: Difference between level and trigger?
« Reply #1 on: May 17, 2010, 11:40:17 AM »
The EasyPLC Help says:

Level activation: the coil is activated by level, this means that whenever the condition is true the reel will be executing

Trigger activation: the coil is activated by flank (trigger), this means that the coil is executed only one time, when the segment is true for the first time and it doesn't execute again until the segment doesn't make the transition FALSE/TRUE again

I will try to explain you with an example:

---| INP 1 |-------------------( DAT1 +1)---|

If the coil is activated by level mode, the dat1 will be added 1 to its value always that the Input 1 will be true. The speed of the addition will depend only of the scan cycle of the PLC. This is not a good solution for a controlated situation.

If the coil is activated by trigger mode: only when the Input 1 pass from 0 to 1 the addition is made.

Some coil controls can need this behavior, like data stack, blocks or configurable blocks. Typing the '!' command you indicate if this component will be activated by level (!) or by trigger.

---| INP_1 |-------------------( DAT1 +1)---| activated by trigger (default)

---| INP_1 |-------------------( DAT!1 +1)---| activated by level

Other example the simple segment:

---| INP_1 |-------------------( OUT 1)---| How it works? by level or trigger. The out coil will work by default by level, because if the input 1 is On the Output 1 will remain to 1 and if Input changes to Off the Output 1 will change also to Off.

This means that some coils can have a default behavior different from others.