Siemens PLC

Siemens S7-200 – Getting Started with Siemens S7 PLC’s

The Siemens S7-200 is a low-cost option for starting PLC programming. Its straightforward design and limited functions make it approachable for beginners, while still giving you reasons to choose it. This guide takes you through getting started with the S7-200 and programming it.

Siemens calls its PLC product line S7 or Step 7. The smallest model is the Siemens S7-200 PLC. Other models in the line include the Siemens S7-300, Siemens s7-400, Siemens S7-1200 and the most advanced system, Siemens S7-1500.

The S7-200 is Siemens’ most affordable option, although newer models are available. If you want to take PLC programming further, consider the Siemens S7-1200 Starter Kit. Its updated STEP 7 Basic TIA Portal gives you a more advanced place to begin learning.

The focus here is 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

Why Use The Siemens S7-200 PLC?

Here are my reasons for recommending the Siemens S7-200 PLC as a starting point for PLC programming. This relatively small model is Siemens’ cheapest and has a limited set of built-in functions. Even so, it has clear advantages over other inexpensive PLCs.

Relatively cheap PLC
Easy to program for beginners
Build on the Siemens platform

The Siemens S7-200 is inexpensive and easy to work with. As the examples below show, connecting and configuring it is straightforward, as are programming and debugging. After a short setup of the programming environment, you can start writing ladder logic for the S7-200.

Much of that ease comes from using Siemens STEP 7 Micro/WIN to program the PLC. I’ll explain the programming software in more detail later.

Let’s start with the modules available for the S7-200 PLC system.

Siemens S7-200 CPU modules

Siemens S7-200 PLC has several CPU modules available.

Every S7-200 system needs a CPU module. This module contains the PLC hardware that stores and runs your program. Without it, the PLC cannot run the program you write.

The S7-200 has several CPU module options. Some have only digital inputs and outputs, others include analog inputs and outputs and some support expansion modules.

CPU 221

CPU221 module from the Siemens S7-200 PLC series.

6 digital inputs
4 digital outputs
Not expandable with modules
Siemens article number: 6ES7211-0BA22-0XB0

CPU 222

Siemens S7-200 CPU222 module.

8 digital inputs
6 digital outputs
Up to 2 expansion modules
Siemens article number: 6ES7212-1AB22-0XB0

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CPU 224

CPU224 PLC CPU module from the S7-200 series.

14 digital inputs
10 digital outputs
Max. 7 expansion modules
Siemens article number: 6ES7214-1BD22-0XB0

CPU224XP

Siemens S7-200 CPU224XP module.

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

Siemens S7-200 CPU226 module.

24 digital inputs
16 digital outputs
Maximum 7 expansion modules
Siemens article number: 6ES7216-2BD22-0XB0

Expansion Modules for Siemens S7-200

Adding modules to the CPU lets you adapt the Siemens S7-200 to your needs. For extra inputs or communication capabilities such as Profibus, choose the appropriate expansion module. This lets you extend the PLC’s functions to suit the work you need it to perform.

This arrangement of PLC modules is familiar in Siemens systems: a CPU module forms the base, with other modules adding functions.

Selecting modules lets you give the Siemens S7-200 the functions you need. I like this use of PLC hardware, and it helps explain the Siemens S7 platform’s popularity. Many good PLC programming books also cover Siemens PLCs.

Input and Output Modules

Siemens S7-200 DI/DO module.

Input and output modules add more connections to your S7-200 CPU. You can choose separate modules or an input/output module that combines both types.

Sensor Specific Expansion Modules

Expansion modules are also available for particular sensor types. A thermocouple module, for example, lets you use one of the thermocouple types to measure temperature with your Siemens S7-200 PLC.

Communication Modules for S7-200

Siemens S7-200 communication with PROFIBUS and AS-Interface.

For PLC communication, the Siemens S7-200 supports network interface modules. Options include interfaces for the ASI bus and PROFIBUS networks as well as Ethernet.

Each network interface module uses standard connectors for its protocol. Ethernet, for instance, uses RJ45 connectors to connect the Ethernet cables. These modules also allow communication with other Siemens PLCs, including Siemens LOGO and S7-300 and 400 models.

Siemens S7-200 Programming Software

STEP 7-Micro/WIN 32 for PLC programming with Siemens S7-200

For me, the programming software is one of the main advantages of the Siemens S7-200 PLC. The S7 PLCs are programmed with STEP 7-Micro/WIN.

The S7-200 programming software is designed to be easy to use. It lets you program in standard PLC languages that follow IEC 61131. With STEP 7-Micro/WIN, you work with those standard languages in an environment intended to make programming straightforward.

Ladder Logic (LAD)
Function Block Diagram (FBD)
Instruction List (IL) in Siemens PLC’s called Statement List (STL)

These PLC programming languages include a range of instructions. They cover simple binary instructions and word operations, program control using master control relays (MCR) and even PID-loops.

Programming the Siemens S7-200 PLC

Getting started with Siemens S7-200 programming is fairly quick. Connecting it to your computer and uploading your first PLC program need not take much time.

The video below shows how to create a simple ladder logic program and upload it to a Siemens S7-200 PLC. With the RS485-based Siemens PPI (Point to Point Interface), you can connect to the PLC and upload a simple program within minutes:

If you run into COM-port problems, perhaps while using a USB COM-port, the following video can help:

Setting Up a Project and Symbol Table

In STEP 7-Micro/WIN, begin by creating a project for your S7-200 PLC. Part of setting up that project is selecting the type of CPU you have connected, so the project uses that model.

For a CPU224, for example, select that model in the project. Next, create a symbol table listing every PLC address used in the project. The table has 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.

Most Siemens SIMATEC PLC projects use a symbol list like this. When programming in ladder logic, you see the symbol name alongside the PLC address. This lets you identify the device connected to an input or output, or the function of a memory bit.

Siemens S7-200 Ladder Programming

Once your symbol list is ready, you can begin writing the PLC program. For beginners, my preferred starting language is ladder logic (LAD).

STEP 7-Micro/WIN keeps the instructions in a toolbar on the left. The basic bit logic category contains all the standard ladder logic symbols you will need.

Easy Program Edit in Run Mode

STEP 7-Micro/WIN lets you edit the program while the PLC is in run mode. On an S7-200 PLC, this means you can see the effect of each edit immediately.

Have you ever used an S7-200 PLC?

Leave a comment below with any questions about the Siemens S7-200 PLC or its STEP 7-Micro/WIN programming software.

If you have used an S7-200 in a project, tell us about the project and why you chose this PLC.

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