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Ladder Logic VS. Functional Block Diagrams

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#1 geometrixeng


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Posted 27 March 2012 - 01:31 PM


Can you do everything using ladder logic that you can do using FBD?

Can you do everything using FBD with SFC's that you can do using FBD without SFC's?

I generally have repetitive processes that essentially move from top to bottom (i.e. using SFC's) with inputs and timing all along the way.

I do not yet know ladder logic, but I have tinkered around with FBD for a while. I am no expert using FBD whatsoever. I am just wondering if there is a preferred method.


#2 Jesus Miranda

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Posted 04 April 2012 - 11:09 AM

Hello geometrixeng.

Ladder language is limited in the case of the Millenium 3. There are certain things that you can not do:
  • You can not use the analog inputs
  • You can not do any mathematical operations
  • You can not use the Display function block, only the Text function block, which has less flexibility
Also, on FBD you have a lot of application specific function blocks that are not available when using Ladder. In general, we only recommend Ladder for very basic programs.

As for SFC, you certainly can do sequential operations using standard function blocks but SFC makes it a lot easier.

Best regards,

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