Siemens S7 Ladder Logic (Beginner)

[SteveOll]

Hi I have just started using Siemens S7 PLC for a mechatronics degree. I have used Matushita PLCs before but I am having difficulty with Siemens S7 ladder logic. I am trying to cycle a double acting pneumatic cylinder using a physically latching start switch and the cycle has to happen only once and then the start button has to be pressed again for the cycle to repeat.

I know that it is very easy to achieve this if the start button is non-latching, but i have spent hours trying to figure it out
( ) but I just end up with the cycle repeating automatically.

Can anyone give me any pointers regarding this? Thanks

 

[PeterW]

Try the one shot bit

 

[JOLTRON]

If you provide more details about what you are trying to do, or what is not working, someone may be able to help you.

Also post any work that you have completed so we can see what you have going on.

 

[tahir4awan]

Generally in industry non latched contactor (magnetic switch) are used and latching is performed through programing. I would suggest you to latch and unlatch your switch through programming.

 

[RheinhardtP]

So you have a latching start,Do you have sensors on the cylinder to determine the position?

When you say cycle i assume you mean extend cylinder to a limit and then back to the start position.

I agree with Peter you would require a leading edge detector to ensure that the code does not repeat itself. I would then set a memory bit Called Cycle. With this Energize the "Open" Output. When you hit the "Open" Limit you can de energize the "Open" Output , Energize the "Close" Ouput. And upon reaching your "Close" Limit Clear the cycle bit.

The Leading Edge will have toi be cycle to run the cycle over again.