In this lesson, I’m going to write a PLC program that can start and control the heavy
three phase electrical motor with the star-delta starter method. To assist in learning this
concept in more depth, I’ll write the program in two different ways and then test each of
the programs online with the PLC simulator to see if they work as needed. So let’s get started.
To get started with programming I click the
SIMATIC icon on the desktop. In software environment, the first thing I
need to do is create a new project. To do this, from the “file” menu, I select “new”.
In the “new project” window I’ll give my project a name and then click okay to create
the new project. In the next step, I need to define what type
of S7 PLC I’m going to use for this project. To do this I first click on my project and
then from the “insert” menu I select “station”. There is a list of all the stations that I
can choose from for my project. Now which one should I choose?
The CPU that I have in the actual environment is a “315-2DP”. The 300 here shows that
my PLC is a “S7 300” PLC so here I should choose “SIMATIC 300 Station”.
If I open the project tree, you see that a “S7-300” PLC has been added. I’ve defined
the type of PLC that I’m going to use in this project but what about the other PLC
modules? The next step is to define the PLC modules
within the software that I have in the actual environment. To do this I select “station”
here and then double click on “hardware” in the right side window.
My PLC is an S7-300 so I have to choose my modules from the “SIMATIC 300” subfolder
here. The first thing that I did in the actual environment
was to install a rack that will hold my PLC modules. This is the same for the software.
To define the PLC modules I need to have a rack in the software. To add a rack I’m
going to open the “rack 300” folder and then double click “rail”.
Now I have a rack that contains 11 slots. The first module that I placed on the rack
in the actual environment was a 2 ampere power supply that powers the CPU and the I/O modules.
To place the same module on the rack in software I open the “PS-300” folder and double
click on this 2 ampere power supply. I have to place the CPU on the second slot
so to do this I open the “CPU 300” folder. There is a list of all S7 CPUs that I can
use. My CPU is a “315-2dp” so I should open this folder here.
As you see, there are different order numbers for this CPU listed, which one should I use?
To do determine which one to select, I have to see what the exact order number of my CPU
is and then choose the same CPU here and put it on the rack.
Let’s assume that the order number of my CPU is “315 2AF02 0AB0” so I need to choose
this CPU here and place it on the rack. Since my CPU has a DP port, as soon as I place
it on the rack, this window opens up to help me create a Profibus network. I don’t need
this type of network for this project so I click cancel.
Because this CPU has a DP port, an extra “X2” row has been added to my rack here.
In the lower window, you have access to more information about the modules you have installed
on the rack. In the next lesson I’m going to add the
input and output modules to the rack and then download the hardware to the PLC.
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