An Introduction to Omron PLCs

A basic understanding of the features and capabilities of the Omron family of PLCs and hardware.

There are dozens of manufacturers of Programmable Logic Controllers that are used in the automation industry. One of the leading makers of compact PLCs for machine automation is Omron PLC.

Omron offers a flexible line of scalable industrial PLC controllers for use in single machines or as part of larger machine control installation.

Standard Omron PLC models

Omron offers several models of PLC hardware that provide several processing and I/O options for small to large machine automation systems.

Standard Omron PLC Models


The CJ2M line of PLC processors and I/O have a modular design and support more than 2500 digital and pulse input and output I/O points wired to I/O cards in local and remote racks. Every CJ2M CPU model supports a large number of steps of programming logic. 

CJ2M line of PLC processors

The 10 separate CJ2M models support from 5000 to 60,000 program steps of programming logic. 

CJ2M steps of programming logic


For smaller, single-machine installations, the CP2E-series of micro-PLCs is a good choice, with up to 60 points of onboard I/O. I/O expansion models can extend its I/O capabilities, including analog and temperature inputs.

CP2E onboard IO

As with the CJ2M CPU, the CP2E PLC can support large logic programs.

CP2E steps of programming logic

CP1H and CP1L

The CP1H and CP1L micro-PLCs are designed for compact machines, such as case-packers and stretch-wrappers.

CP1H and CP1L Omron PLC

These CPUs have the capability of high-speed counters and pulse outputs which allow this PLC model to perform multi-axis positioning control. Both models come with onboard and add-on I/O, including digital, analog, and temperature sensor units.

CP1H and CP1L


For larger systems, the CS1 CPU has a maximum capacity of over 5000 digital I/O points over seven expansion racks. Any combination of up to 80 I/O modules and communication modules can be mounted in any position in the I/O racks.

CS1 Omron PLC

The CS1 allows the use of IEC standard Structured Text and ladder language, which allows flexibility in how programs are written.

CS1 IEC standard language

Other important capabilities of a CS1-based system is its support for position and motion control modules, analog input and output modules, loop control modules, and interrupt and safety relays.

CS1 modules

The CS1D variant provides several dual-redundancy options. CS1 models allow for hot-swapping of CPUs, power supplies, and I/O units to minimize downtime.

Omron PLC Ethernet interfaces

Omron PLC communication options

Ethernet interface

Each of these PLC families has specific models that can have one or more Ethernet interfaces with the Ethernet/IP data link function.

Omron PLC Ethernet interfaces

Ethernet/IP is an Industrial Ethernet communication protocol widely used by Rockwell and other automation PLC and device manufacturers that allows for structured, tag-based communication.

Serial communication 

All PLC models support serial RS-232, RS-422, and RS-485 communication through the addition of option boards. This allows for additional device types, such as motion controllers, to be interfaced directly to the PLC.

Omron PLC serial communication Options

CompoBus/S network 

In addition, the CP1E, CP1H, and CS1 CPUs support Omron’s proprietary CompoBus/S I/O subsystem, which allows for high-speed, long-distance remote I/O connections.

Omron PLC CompoBus

DeviceNet and Profibus-DP

DeviceNet and Profibus-DP are supported by the CS1 CPUs so that additional device types, such as weigh scales and motor drives, can be connected to the PLC network.

Omron PLC DeviceNet and PROFIBUS-DP

CX-One software

The CX-One software suite allows users to build, configure, and program Omron PLCs, HMIs, motion-control systems, and networks using only one software package.

Additional software packages can be purchased to provide functionality for supervisory machine visualization and control, communication drivers and interfaces to 3rd party HMI’s, OPC server capability, and development software for Omron’s LD, HD, and mobile robots.

CX-One software can be installed on Windows 7 Service Pack 1, Windows 8.1, and Windows 10.

CX-One Software

Example system hardware configuration

As an example, we will configure a small PLC system to control a series of conveyors, motors, and sensors used for transporting boxes from a case packer to a palletizer. For this example, the conveyors and associated equipment have a total of 50 digital inputs and 25 digital outputs. 

To simplify programming, troubleshooting, and maintenance, we want the process to be controlled by a single CPU. We will locate the PLC and I/O cards in a single panel. Remotely located I/O is not required for this simple process.

Example System

Omron PLC Example system

We will choose the CP1L-EM30DR-D CPU which features relay outputs and an Ethernet port for networking connections.

Example System networking connections

To service the bulk of the I/O, we will choose a variety of CP1W 24VDC input, output, and mixed I/O modules. All outputs will be relay outputs. Each of the expansion modules will require an I/O Connecting Cable.

To complete the network, we add a 5-port network switch with failure detection, a small HMI panel with an Ethernet port, and a 20A DC power supply. This provides the functionality we need in a compact, easily installed, and configured package.

Example System Hardware Configuration


This article has provided a basic understanding of the features and capabilities of the Omron family of PLCs and hardware. Once you understand the requirements for your process, choosing the right CPU, communication interfaces, and I/O modules should be easy to do.

If you have any questions about the Omron PLCs or PLCs in general add them in the comments below. As you know, we read each and every comment and reply to it in less than 24 hours!

Got a friend, client, or colleague who could use some of this information? Please share this article.

The RealPars Team

By Scott Sommer

By Scott Sommer

Automation Engineer

Posted on Jan 25, 2021

Ted Mortenson
By Scott Sommer
Automation Engineer

Posted on Jan 25, 2021

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