Katerina

Hello! I have written a plc program in ladder which is used for controlling/coordinating a production process in a manufacturing cell (including a robot , turning machine and milling machine and intermediate buffers). For the control of the whole cell I am using a ‘central’ plc which sends and receives signals to/from the robot and the other machines. Moreover the signals that are sent to the robot and other machines are more than one .For instance, different signals sent to the robot referring to different movements which should made by the robot according to the program). As you can see in the picture I have attached (which is only a small part of the 'central' plc program) Rst_I_A_T  is the output from the central plc (input to the robot) telling the robot to start a specific movement and Rfin is the input to the central plc (output from the robot) telling the central plc that this movement has been finished. Questions : 1)      Generally when we want to control a robot in an industry which should be coordinated with other machines (and not have a continuous standard operation) do we use a separate plc connected to the robot? 2)      Is the way I am using Set and Reset for the input to the Robot Rst_I_A_T right ? I mean Rst_I_A_T is sent as a continuous signal to the robot and is reset by by the central plc when it receives Rfin from the robot. Is that right? (Actually the task that I am doing is only in a theoritical level but I would like to be as right as possible!)

ΗI! Thank you for your answer! As you can see, my knowledge in robotics and communication between controllers is limited. So, I really appreciate somebody's opinion who has practical experience in these issues! So, if you had to coordinate/control a robot and and other machines which should work together properly (so as not to have collisions/deadlocks and mininmize waiting times ) wouldn't you use a central plc?? I have seen somewhere that in these cases they  also use a separate plc for the robot.

Well..after some changes I made, it seems to work ok (so far)! I did the simulation using force on/off very carefully keeping track of the outputs. I hope this is enough! Now I am thinking of another issue that has to do with communication of the program I have made with other plcs. Ι have posted it in another topic of this site regarding robots.  

Hi! I would like to ask if I can use SET/RESET commands more than one time (for the same value/address) in the same program.I have already created the program but there are a lot of warnings like: WARNING: Duplicated output -  RSET 200.00 at rung 1 (6, 5)  WARNING: Duplicated output -  SET 100.00 at rung 1 (6, 7)  WARNING: Duplicated output -  RSET 200.01 at rung 2 (6, 3)  WARNING: Duplicated output -  RSET 200.00 at rung 2 (6, 5)                             ....................... Do these warnings have to do with using set or reset many times for the same value? I don't want  to put every set and reset of the same value together because this causes changes in the order (and consequently the priority)of the rungs.(I noticed this when I tried to do a simulation) (I have attached a picture of a small part of the program so you can see clearly what I mean)

Hello! Thank you for your answer! Regardless of using KEEP or SET/RESET and regardless of the communication protocol used , I would like to ask you : Is the 'policy'  I have used for  signal transmission between the robot and the central plc is correct /realizable??? 1) The central plc sends a signal Rst_I_A_T to the controller of the robot  2)The robot controller receives the signal and performs the corresponding motion (Rst_I_A_T is still on) 3) The robot controller sends signal Rfin to the central plc when motion is finished (Rst_I_A_T is still on) 4) When the  central plc receives Rfin from the robot it resets the Rst_I_A_T signal. So the robot stops seeing it.

Τhank you for your answer! To be honest, I got confused ! Regarding the first  picture : 1)       the rungs of the first picture seem to me very strange. I mean I would never put the open |  | and closed contact |/| of the same bit (CF113) connected to the same coil (W1.00). Is this an alternative way instead of using set/reset?   2)      I cannot understand why the second rung determines the state of the coil. For instance, in the very first example#1 in your picture ,considering that the plc starts ‘reading’ from the top rung to the bottom, the W1.00 should be activated (because it is connected with an open contact and it is the first rung) and stay activated for ever given that we have an always on contact.

Hello! Is this methodology professionally avoided though? What I am trying to do actually is translating Petri Nets into ladder .(Petri Nets are a mathematical way of programming  automated production systems in order to avoid deadlocks) So,  I use this repeated SET/RESET for variables  because I am following a standard translation methodology. What are  STEP/SNXT instructions and how could they help me ?

What exactly do you mean by saying ''not work as expected. Only the last instance will be evaluated'' ?? I have tried to do some kind of simulation using force on/off.It seems to work as expected until a point where something goes wrong ( that is what I am trying to find out right now )

I am using version 9.2 of Cx-programmer. I want to compare the current value of a reversible counter(CNTR)  with the value 0. I tried to create a comparator by writing [CMP C7 0 ] and then in the next rung I connect the comparator with a coil ( which should be energised when the comparator is true). But there is an error : ERROR: Coil is not positioned correctly at rung 155 ( 6, 0 ).  ERROR: Function 'CMP(020)' is positioned incorrectly. at rung 155 ( 0, 0 ).   I have attached apicture which shoes clearly what I have done!

Thank you all for your answers!!

Hi! Thank you for your answers! It seems that Cx Simulator has been installed. The button ''Online with Simulator'' is active but when I press it it says : ''The selected port does not exist.Do you wish to find any available serial port and go online?''  The PLC model that I am using right now in my projest is CS1G-H (Which I actually set for no specific reason). Should I change it to another type??

Thank you for your answer! What do you mean by saying''NO contact of the appropriate flag (<, <=,=,>=,>)'' ? Is that what you told me to do? (see the picture)  

Hi I am new to using PLCs. I am trying to find a way to simulate ladder programs offline because I don't have a plc module. I read in the introduction guide that this can be done either with the simulation connection button (which  cannot be activated in the version  Cx-one 4.10.0005 that I am using) or with the switchbox utility which seems to work in my version. But unfortunately (after searching in manuals and on the internet) I cannot find any more information on how to use the switchbox. Can anyone tell me where I can find more information or a tutorial about how to use this tool ?