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>>Message imported from previous forum - Category:General Items<< User: mchartrand, originally posted: 2018-10-17 18:37:04 Id:75 This is a re-posting from the obsoleted (October 2018) "Schneider Electric Telemetry & SCADA" forum.
**krugman21: _I was approached by my employer about a week ago, and asked to set up a SCADA system on pipeline run. I have written some applications in c#, but am completely unfamiliar with SCADA Systems and ladder logic. I am am trying to figure out how these systems work and exactly what I will need to do. A few questions I have is, will I need to program both the SCADAPack and the HMI? If so, are both of them programmed using the same language? Is Isagraf just a programming environment? Do I need to use both telepace and isagraf? Can someone just lay out the basic steps from the beggining to finish? From what I have read so far, it writing ladder logic, and programming PLC's is much different than what I currently do with object oriented language._**
zack123: This is the basic idea. To actually do these things, it will require hours of clicking around and trying things. These steps must be done in parralel. Write the PLC program, this can be done in ladder logic, C, or some other type of programming language as allowed by the PLC in question. The PLC should then have variable "Tags". Clear SCADA calls them points. These points, or in other words, externally addressable variables are controlled or displayed with an HMI or SCADA software. The PLC program will be written to respond to changes in these variables or to update the values of these variables so that the displays on the SCADA get updated. Variable Tags or "Points", are downloaded, and if changed by the user, uploaded by the SCADA software at a periodic rate. Often this is done with "Modbus" protocol which may be carried over a serial connection or via TCP/IP. Other protocols such as "Profibus" are available.
**_krugman21: I appreciate that, it has helped me understand the process better. Another question I have, is the same program that is written for the PLC the same as what is used for the HMI. For example the if I write the code for PLC in ladder logic, is it that same program that I am interacting with on the HMI? From what I can tell, ladder logic is graphical, so i wasn't sure if that is the GUI that the user is interacting with on the HMI. Or if by graphical they just mean that the "writing" of the program is done graphically.._**
zack123: No, they are two different computers with two different programming languages.
**_krugman21: Is Isagraph used to program the PLC or the HMI, or both?_**
bwootton: isagraph and Ladder Logic are 2 differnet ways to program the ScadaPack PLC.
The HMI has to be programmed seperatly.
Ex. PLC is programmed to calculate a PSI reading, start pumps, etc. Basically calculating and controling stuff.
HMI will be programmed to show that PSI reading, the pump status, etc. It is just a graphical interface to the user, Human Machine Interface.