Siemens S7-200 – Getting Started with Siemens PLC
The Siemens S7-200 PLC is a very popular choice when you start PLC programming. It is the cheapest PLC from Siemens, and it is very easy to begin programming. The Siemens S7-200 has a limited variety of functions, but it certainly also has a lot of advantages. With this article, you will be ready to start configuring and programming the Siemens S7-200 PLC.
As you may know, the PLC product line from Siemens is named S7 or Step 7 PLCs. The smallest PLC model is the Siemens S7-200 PLC. In the line of PLCs, you will also find the Siemens S7-300, Siemens s7-400, Siemens S7-1200, and the most advanced PLC system in the line; Siemens S7-1500.
Even though the S7-200 PLC system is still the cheapest it is now the latest series of Siemens PLCs. Siemens has made a new kit for learning PLC programming. If you are serious about learning PLC programming you should take a look at the Siemens S7-1200 Starter Kit, which comes with the latest STEP 7 Basic TIA Portal (version 13).
This article will explain the Siemens S7-200 PLC.
Disclosure: Some of the links in this post are affiliate links and if you go through them to make a purchase I will earn a commission. I link to these products because of their quality and not because of the commission I receive. The decision is yours, and whether or not you decide to buy something is completely up to you 🙂
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Why Use The Siemens S7-200 PLC?
First of all, I would like to give you a few of the reasons why I think you should start PLC programming with the Siemens S7-200 PLC. Because even though this relatively small PLC is the cheapest one from Siemens, and therefore has a limited amount of built-in functions, this PLC has some clear advantages over other cheap PLC’s.
- Relatively cheap PLC
- Easy to program for beginners
- Build on the Siemens platform
Besides being cheap, Siemens S7-200 PLC is also quite user friendly. If you read further down this article, you will notice that this Siemens PLC is actually very easy to connect to, configure, program, and debug your programs. You can be programming ladder logic for Siemens S7-200 after just a quick configuring of the PLC programming environment.
The reason, this PLC is so easy to work with is that you use Siemens STEP 7 Micro/WIN to program the PLC. More about that piece of PLC programming software later in this article.
First, a little look at the various modules you can get for the S7-200 PLC system.
Siemens S7-200 CPU modules
The first module for the S7-200 series is the CPU module. This is a necessary module, and you will always need at least one of these. A Siemens S7-200 CPU module contains the CPU PLC hardware. This is the module that has your PLC program stored and runs it.
There are several CPU modules for the S7-200 available. Some with digital inputs and outputs only, some with analog inputs and outputs, and some with expansion modules available.
CPU 221
- 6 digital inputs
- 4 digital outputs
- Not expandable with modules
- Siemens article number: 6ES7211-0BA22-0XB0
CPU 222
- 8 digital inputs
- 6 digital outputs
- Up to 2 expansion modules
- Siemens article number: 6ES7212-1AB22-0XB0
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CPU 224
- 14 digital inputs
- 10 digital outputs
- Max. 7 expansion modules
- Siemens article number: 6ES7214-1BD22-0XB0
CPU224XP
- 14 digital inputs
- 10 digital outputs
- 2 analog inputs
- 1 analog output
- Up to 7 expansion modules
- Siemens article number: 6ES7214-2AD23-0XB0
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CPU224XPsi
- 14 digital inputs
- 10 digital outputs (sinking outputs)
- 2 analog inputs
- 1 analog output
- 7 expansion modules
- Siemens article number: 6ES7214-2AS23-0XB8
CPU226
- 24 digital inputs
- 16 digital outputs
- Maximum 7 expansion modules
- Siemens article number: 6ES7216-2BD22-0XB0
Expansion Modules for Siemens S7-200
Most of the CPU modules for the Siemens S7-200 can be expanded with other modules. Those modules can have different functions. You can expand the CPU with just the functions you need, whether its PLC communications like Profibus or extra inputs.
The Siemens PLC system is well known for this system of PLC modules. A PLC CPU module as a base, and then some modules for further functionality.
With the modules, you can get the functionality you want with the Siemens S7-200. This is a great way to make use of PLC hardware, and it’s one of the reasons the Siemens S7 platform is so popular. There are also a lot of good PLC programming books that discuss Siemens PLCs.
Input and Output Modules
If you want to expand your S7-200 CPU with additional inputs or outputs you can get input and output modules. You can also get a so-called input/output module with both inputs and outputs.
Sensor Specific Expansion Modules
You can also get special extension modules for different sensor types. As an example, you can get an expansion module for a thermocouple, and thereby use one of the thermocouple types to measure temperature with your Siemens S7-200 PLC.
Communication Modules for S7-200
At last, you can expand the Siemens S7-200 system with PLC communication. You can get network interfaces for the ASI bus network, PROFIBUS network, an Ethernet network.
All the network interface modules have standard connectors for each network protocol. For example, the Ethernet network uses RJ45 connectors for connecting the Ethernet cables. The networking modules also lets you communicate with other Siemens PLC’s like the Siemens LOGO and the S7-300 and 400 PLC’s.
Siemens S7-200 Programming Software
One of the biggest advantages of using a Siemens S7-200 PLC is the programming software. The software used to program the S7 PLC’s is STEP 7-Micro/WIN.
The PLC programming software for the S7-200 is made to be intuitive and easy to use. You will be programming the Siemens S7-200 PLC with one of the standard PLC programming languages as described in the IEC 61131 standards. The languages you can use with STEP 7-Micro/WIN is:
- Ladder Logic (LAD)
- Function Block Diagram (FBD)
- Instruction List (IL) in Siemens PLC’s called Statement List (STL)
Within those PLC programming languages, you have a variety of instructions available. From simple binary instructions and word operations to program control with master control relays (MCR) and even PID-loops.
Programming the Siemens S7-200 PLC
Get started programming the Siemens S7-200 PLC can be done quite fast. From connecting the PLC to your computer and uploading your first PLC program shouldn’t take much time.
Take a look at this video to see how you can create and upload a very simple ladder logic example PLC program to a Siemens S7-200 PLC. By using the RS485 based Siemens PPI (Point to Point Interface) you can connect to the PLC and upload a simple program within minutes:
And if you are having issues with the COM-ports (maybe you are using a USB COM-port) you should check out this video:
Setting Up a Project and Symbol Table
Usually, the first thing you would do in the STEP 7-Micro/WIN is to set up a project for your S7-200 PLC. This means that you have to choose the CPU type you are using.
So if you are using a CPU224, that’s what you choose in the project. After doing so, you will be creating a symbol table. The symbol table is a list of all the PLC addresses used in your project. In this table you have three columns:
- Symbol: The name of the address used (Start, Stop, etc.)
- Address: Siemens PLC address you will be using (I for inputs and Q for outputs)
- Comment: Add a comment to help yourself and others understand the symbol.
Making such a symbol list is common practice with most Siemens SIMATEC PLC’s. When you are programming in ladder logic, for example, you will not only be seeing the PLC address, but also the symbol name. In that way, you can always see what is connected to the input or output or what the function of a memory bit is.
Siemens S7-200 Ladder Programming
After you’ve created your symbol list it is time to get to some PLC programming. The language I prefer to start with for beginners is ladder logic (LAD).
When you are programming in the STEP 7-Micro/WIN you always have a toolbar to the left with all the instructions you need. The bit logic instructions are the most basic ones and in that category, you will find all the standard ladder logic symbols.
Easy Program Edit in Run Mode
One of the great features in STEP 7-Micro/WIN is the ability to edit your PLC program even when the PLC is in run mode. You can do this with the S7-200 PLC’s and see the effects of your edits immediately.
Have you ever used an S7-200 PLC?
Feel free to write a comment below if you have questions about the Siemens S7-200 PLC or the STEP 7-Micro/WIN PLC programming software.
If you have used the S7-200 PLC in a project, we would love to hear about it and why you chose this PLC.
