Article summary
The Siemens S7-1200 PLC includes about 20 unique family members. The products are easy to identify once we recognize the relationships between family members. This article simplifies the process and explains how the components may be identified in DigiKey’s catalog. A guided learning activity for educators and students is available.
This article is part of DigiKey’s Siemens PLC and Automation Resource Hub. Visit the hub for more technical briefs on Siemens components, applications, and programming.
Estimated reading time: 3 minutes
Range of the Siemens S7-1200 PLC family
This post helps you navigate the Siemens S7-1200 PLC family including the second generation (G2) and fail-safe (yellow safety) PLCs.
DigiKey is a distributor for the Siemens S7-1200 line of Programmable Logic Controllers (PLC). There are about 20 unique PLCs ranging from the smallest CPU 1211C with 8 inputs and 6 outputs (approximately $410 U.S. single quantity) to the larger CPU 1217C featuring larger memory with 14 inputs and 10 outputs. There are also fail-safe (safety) PLCs such as the CPU 1215 FC (see Figure 1) and the latest G2 PLCs such as the CPU 1214C.
Figure 1: Image of the Siemens CPU 1215 FC operating at the author’s workbench.
Tech Tip: Industrial control systems have a multi-decade service life, consequently we should select a PLC with more capability (processing power and I/O) than strictly necessary.
As a side benefit, if an I/O pin fails, the technician may be able to restore functionality by swapping to an unused pin provided the code is strictly organized with clear single location I/O mapping.
Siemens PLC selection is complicated by multiple descriptions
There are two general methods to identify a Siemens PLC including:
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CPU along with the I/O description such as CPU 1212 DC/DC/RLY
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Full part number such as 6ES72121HG500XB0
Both naming conventions are valid as they point to the same PLC, yet both can be difficult to use when it comes to locating a specific part. We will focus on the CPU descriptor as it is easier to remember and decode.
Tips for locating a Siemens PLC
This section describes the hierarchical structure of Siemens PLC family members and then shows how to locate a PLC with DigiKey’s search tools.
Tiered functionality within the S7-1200 family
The Siemens S7-1200 are grouped according to overall capability using a CPU classification. This provides an easy way to remember family relationships.
This list presents the PLCs in ascending order in terms of memory and I/O count:
- CPU 1211: Low-cost entry level with minimal e.g., 8 inputs and 6 outputs
- CPU 1212: standard and G2
- CPU 1214: standard and G2
- CPU 1215
- CPU 1217: largest memory along with 14 inputs and 10 outputs
In addition, the PLCs are classified as either standard or fail safe. Standard models are identified with a C as in CPU 1214C while fail-safe PLCs are identified with FC as in CPU 1214 FC.
Unfortunately, the G2 PLCs are not easily identified using the CPU descriptor. However, this is a minor concern as we can use the pictures to quickly identify the desired PLC. Likewise, we can use the parametric tools to locate the desired power supply input and output type. If necessary, we can visit Siemens mall to locate the full part numbers.
How to locate a Siemens PLC using DigiKey’s search tools
Once we know the Siemens CPU family, we can use a twin keyword lookup to find the desired parts. For example, search:
- “CPU 1214 PLC” to locate all PLCs in the 1214 family including standard, second generation, and all fail-safe PLCs. Partial search results are shown in Figure 2.
- “CPU 1214 C PLC” to locate the standard original and G2 PLCs
- “CPU 1214 FC PLC” to locate the fail-safe standard and G2 PLCs
Figure 2: Partial results of a DigiKey search for the Siemens CPU 1214 PLCs including G2 products currently in stock.
Next steps
Be sure to test your knowledge using the guided learning activity. It provides a framework for students and educations for a deeper understanding of the Siemens S7-1200 model numbers.
Parting thoughts
There is no “best” PLC. Instead, we see a variety of PLCs each suited for a particular application. This is reflected in the large number of PLCs within the Siemens S7-1200 family. We also recognize that the S7-1200 is bookended by the Siemens LOGO! and the powerhouse S7-1500.
Best wishes,
APDahlen
Related articles by this author
If you enjoyed this article, you may also find these related articles helpful:
- Make Your PLC Play a Song: Mastering Siemens PLC Memory Arrays
- Building a Structured Text User-Defined Function Block (UDFB) using Siemens TIA Portal
- What is a motor starter’s solid-state overload relay?
TL;DR
- DigiKey is a distributor for Siemens S7-1200 PLCs ranging from CPU 1211 to CPU 1217 including fail-safe and G2 models.
- Searching by CPU type (e.g., 1214 FC) is preferable to decoding and then searching by the full part number.
- The DigiKey search engine is designed with an AND-based filtering logic allowing us to locate products using focused keyword searches such as, “CPU 1215 FC”.
About this author
Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET-accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians. Dahlen has returned to his Northern Minnesota home and thoroughly enjoys researching and writing articles such as this.