How to do looping in PLC using Ladder logic?

[pakiboy]

I m using S7(Siemens PLC) . I wanna ask how can we do looping using Ladder lagic? Say i want to make LED flesher which flesh LED infinite times or 10 times !! is there any possibility to make this logic on ladder logic or I have to use STL ??

Regards

Awaiting for swift responce.

 

[FvM]

Re: Looping in PLC

A similiar logic shouldn't be realized with loops in ST or any other PLC programming language. A loop effectively holds execution of PLC cycle.

Use a counter or a count variable and a timer respectively one of the available systimer ticks instead. This should be basically possible with any PLC programming technique.

 

[pakiboy]

Re: Looping in PLC @ FvM

Sorry FVM ...i could not get ur point clearly abt execution Cycle of PLC ? I m a beginner ..plz elaborate your point a little bit more!!!

Regards

 

[FvM]

Re: Looping in PLC

The basic concpt of a PLC is executing the main code (OB1) repeatedly. Acceptable cycle time depends on the application, with slow processes several 10 ms may be O.K. Blinking the LED in a loop would extend cycle time to several seconds, acceptable only for a PLC that has no other outputs than the blinking LED.

I'm sure that you can find some blinker examples in PLC tutorials that are compatible with regular operation.

 

[gerdfield]

Re: Looping in PLC

I think you can use special function relay to achieve it