hello guys

In another topic i post my problem and a reaction was that my problem had something to do with a sequencing problem. I didn't found a solution for it on this forum so i decided to make a new topic.

to simplefy my project:  my project is a conveyor with on the right site sensor R and on the left site sensor L 

if i put a can on the conveyor in front of sensor R the conveyor takes the can to sensor L.  when the can is being detect by sensor L the conveyor start to rotate the other direction and takes the can back to sensor R. when the can reaches sensor R i want the conveyor to stop and leave the can in front of sensor R. but instead of stopping the conveyor starts the cycle again and takes the conveyor again to sensor L. the conveyor is repeating the cylce over and over again.  as said before, i want the conveyor to leave the can in front of sensor R and the cycle may start again if i remove the can and put back in front of sensor R again. 

now i managed to get this working in the way i wanted with a timer and lots of contacts and pulses. but during programming i was wondering/convinced that it must be possible to get this working without the help of a timer and only by using contacts and pulses.

if anyone understand me, is my object possible without help of timers

gr gerard

William,

With puzzelin a lot with my program. it changed a lot from the thing it was when i started. now i thrown it away i also knew that there was someting fundamently wrong in it. and as i study your suggestion about how i should start.  your suggestion confirms for me that there was something wrong. if it works, i post it 

thank you that you are helping me 

for a big part (the basis) i understand your methode but somethings are for me some mystery 

-in the first network the third item, what is that and for what is it

-that move instruction in the end of network 1,  for what is that

-you use a datablock, can you show a screenshot of it 

-first i had siemens step7 v5.5 but now i have tia13 and in your screenshot i saw something                     like:"    #steps.%X1"   in my older version i knew exactly what it was.  it's a bite used in a datablock  right? . can you correct me if i'am wrony

hope i didn't ask to much

gr gerard

gerard32

-in the first network the third item, what is that and for what is it

-that move instruction in the end of network 1,  for what is that

-you use a datablock, can you show a screenshot of it 

-first i had siemens step7 v5.5 but now i have tia13 and in your screenshot i saw something                     like:"    #steps.%X1"   in my older version i knew exactly what it was.  it's a bite used in a datablock  right? . can you correct me if i'am wrony

Gerard,

Thank you for acknowledging my humble efforts. I am very sorry if this discussion is causing you to doubt your own efforts - please this is not my intentions. Do remember that each person has its own style of developing an answer to a problem. From practice our answers (coding) become more efficient.. but rarely without error.

background
#steps is declared as a STATIC variable of WORD type.  #steps is used to keep track of the sequence progress. In the program piece the variable is used in WORD format and BOOL format. In the example only one bit is ON within the WORD.

- in the first network the third item
You are looking at a compare function. The network makes sure that no sequence step is active before initializing a new sequence run.

- that move instruction in the end of network 1
For the situation you do not need to use the MOVE instruction. The MOVE instruction was used here to show how a sequence can be initialised. This is however a good way to re-initialise a sequence.. where you can ignore where the sequence was at that moment.

- you use a datablock, can you show a screenshot of it
The variables in the FB is not important. Only #steps is important. The #condition_? variables are suppose to be replaced by your own pieces.

- #steps.%X1
That is an addressing method called "slicing". This method is not available for all PLCs.. but you can use it in S7-1x00. It is one of the  reasons why it helps if we know what PLC you need to program for. In our case study,  we are able to hande the variable as WORD and BOOL.

w

William,

with this i'am going to try and see if i can get this work on my project

still somethings are a bit unknown for me,

i give it a try and come back to you 

gr gerard

gerard32

With this i'am going to try and see if i can get this work on my project

still somethings are a bit unknown for me,

i give it a try and come back to you

My paid-for responsibilities demands my full attention now - hopefully others will reply to any questions you may have.

See what you can do with what I have given you. Some of the information will seem contradictory if you only apply it to the code segment I have given. But you will do okay if you use the code segment as an incomplete template that is meant as a conversation starter.

Good luck!
w

william

you used steps,  but but what is the difference between using steps and for example a markers (m0.2)

i practice a lot with plc sim, i create ib etc. but how's that with that steps thing. where is that steps..  storing it's data. (maybe i get this part wrong)

gr gerard

gerard32

william

you used steps,  but but what is the difference between using steps and for example a markers (m0.2)

i practice a lot with plc sim, i create ib etc. but how's that with that steps thing. where is that steps..  storing it's data. (maybe i get this part wrong)

gr gerard

Gerard - Good to hear from you.

Yes you are right you are always welcome to use the memory markers.
If this makes sense to you then go ahead.. use them.

The reason I used the #steps variable was to introduce new ideas to you.
#steps is a variable that is a local user created variable that live in an FB.
I will see if I can make some screen captures in a next posting to explain.

Please.. let us return to the marker memory first.

Attached is a demonstration of how MW0 can be used. Note that the demo was done with an S7-1500, but the concepts stay the same. I recommend you try to replicate this for yourself.

Theory...
For Siemens PLC it is important to know that their original memory structures revolve around BYTE structures where 8 bits make up a BYTE. It is also important to know how they number their structures when working with M-flags. As example:

|                                            MD0                                            |
|             MW0                          |                   MW2                   |

|       MB0       |         MB1        |       MB2        |          MB3     |

| M0.7|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||| M3.0 |

However you can use the "slicing" method [FAQ link], as used also in the demo.

That is all I have to say regarding M-flags, until you have  questions.

(to continue in next post - creating variables in FB)

hello..............,

attached is a screenshot of the first and last network of my slicing sequence.  although i understand that set/reset, steps declaration and move instruction.  i just cant get the sequence working in the right way i want it to.

my sequence starts as soon as i put a can on a conveyor in front of sensor i0.0.  the conveyor takes the can through the sequence and than back towards sensor i0.0.  but as soon as sensor i0.0 detects the can again the sequence starts again. but thats not the way i want it.   what i want is that if the conveyor takes the can back to sensor i0.0 again the sequence has to stop.   and may only restart again if i take the can from the conveyor by hand and put it back again in front of sensor i0.0.

i don't know if it's possible what i want, but i've tried a lot and somehow i get the feeling that there must be some kind of trick for it

that stepss.x4 thing in my attachment is from an experiment

gr gerard