Hello everyone,

I am trying to make a loop in ladder logic, and as seen in attached pic. But for some reason everytime I call that FC, my plc stops and gives me an error. Why does it do that? Am I doing something wrong?

Thank you for helping me out!

Definition Handbook

Endless loop

See Loop, Endless

Definition Handbook

Loop, Endless

See Endless loop

.... a PLC is not a PC. If the PLC does not complete its scan cycle in time, the PLC goes into stop. Maybe tell us what you want to do.

William_B

Definition Handbook

Endless loop

See Loop, Endless

Definition Handbook

Loop, Endless

See Endless loop

.... a PLC is not a PC. If the PLC does not complete its scan cycle in time, the PLC goes into stop. Maybe tell us what you want to do.

 

Hi William,

I know it was an endless loop, i was just testing something out but I didn't know it would create this problem. 

AlI am trying to do is to control the belt speed through PLC. On certain condition, I want to start-stop-start-stop the belt so its running really really slow, so thats why i was setting/resetting "running". I thought the loop will be the best way to do that but I might wrong. I also tried the loop with a condition, which will lun the loop for 200 times, but that didn't work either. How can I achieve this? 

what I was thinking if that condition occurs: reset running-have a 500 ms delay and set running (keep doing that in loop for 200 times)

Thanks!

Hello,

agree absolutely with William, pay attention for not overtake that CPU cycle time. If I can give you little help, try making loop with registering f.ex. INT variable, starting from 0, with next condition to overtake f.ex. value 1000. If not reached, then add another +1 to that variable. If reached that 1000, reset to 0 f.ex. This loop is very easy, taking care of CPU cycle clock, but maybe can be not precise exactly (like HW Timer), but works. Try it

Duris_I

<snip>
... If I can give you little help, try making loop with ...
</snip>

Dear friend,

Thank you for jumping in with your help.
If nobody else says so.. I do appreciate it.

Please...
I think I know this user a little. (Sorry) Your words are not enough. You will do the most good if you could code a sample piece of LAD code and post it as an image.

Are you up for it? - my thanks regardless.

Greetings.
w

Hello William,

thnx for your suggestion, but my system is giving to user some idea. It will be better that he will fight with this problem with our 'little' help to finish, then he will be happy that he solved it. I'm sorry but this is my idea, I take your info that you know him, but programmer will be better programmer if try, make tests maybe with little support, not know complet solution, trying think about it. Maybe you understand my opinion, but this probably not belong to topic.

Edit: working with automation from 1995, but never had bad suggestions if I want help to someone, pls understand me...

AlI am trying to do is to control the belt speed through PLC. On certain condition, I want to start-stop-start-stop the belt so its running really really slow,

 JOG would do this without messing up your run logic (I assume you have a drive). Set your JOG speed to whatever low speed you want.  Use 2 timers to make an ON and an OFF pulse or use the built in clock pulse bits.  You can count the ON's and stop whenever you want

@William_B and Darus_I, you both have valid points, but if its too easy, then no learning takes place. 

Jeff Casagrande

AlI am trying to do is to control the belt speed through PLC. On certain condition, I want to start-stop-start-stop the belt so its running really really slow,

 JOG would do this without messing up your run logic (I assume you have a drive). Set your JOG speed to whatever low speed you want.  Use 2 timers to make an ON and an OFF pulse or use the built in clock pulse bits.  You can count the ON's and stop whenever you want

@William_B and Darus_I, you both have valid points, but if its too easy, then no learning takes place. 

@Jeff 
I like your idea for being simple and to the point.

@Duris_I
We all have our own way of learning and teaching.
This post aims as help with no ill will to yourself.

@the_learner_99
Attached is a design idea designed for the S7-200.
It is a basic idea of a sequence machine..
hopefully it is enough clues to have you program your own in the S7-1200.

Good luck.
w

William_B

Jeff Casagrande

AlI am trying to do is to control the belt speed through PLC. On certain condition, I want to start-stop-start-stop the belt so its running really really slow,

 JOG would do this without messing up your run logic (I assume you have a drive). Set your JOG speed to whatever low speed you want.  Use 2 timers to make an ON and an OFF pulse or use the built in clock pulse bits.  You can count the ON's and stop whenever you want

@William_B and Darus_I, you both have valid points, but if its too easy, then no learning takes place. 

@Jeff 
I like your idea for being simple and to the point.

@Duris_I
We all have our own way of learning and teaching.
This post aims as help with no ill will to yourself.

@the_learner_99
Attached is a design idea designed for the S7-200.
It is a basic idea of a sequence machine..
hopefully it is enough clues to have you program your own in the S7-1200.

Good luck.
w

First of all let me thank all of you for you suggestions/help! I have tried a loop with condition (intended to run 200 times as seen in attachment) but for some reason its not working. Can any of you tell me what's wrong with my code? I simply just want to slow down the speed of the belt and I like @jeff your suggestion but I haven't work with PLC much so I will look at jog option. But as of now, i think it will be easier if I just have a loop which will slow down my belt speed by stopping and restarting the belt itself! Please look at my attachment and any suggestion/help would be great!! I am just confused as to why my loop doesn't work! 

or maybe it is working, but just not slowing down the belt? 

Thanks I really appreciate all of your help! 

Hi,why You want to use loop for this....use two timers,create pulse generator,count pulses to 200....

for example look at Siemens pages:  https://support.industry.siemens.com/cs/document/54647747/how-do-you-program-a-pulse-encoder-in-step-7-(tia-portal)?dti=0&lc=en-WW

...to Your loop...how do You reset the output after timer sets?

Have nice day...