Essentials of OMRON CQM1H PLC System

Essentials of CQM1H PLC System: Comprehensive Analysis from Selection to On site Maintenance

In the field of industrial automation, the OMRON CQM1H series PLC has become a classic in the field of machine control due to its compact modular design, powerful plug-in board expansion capability, and flexible network communication function. Compared to the early CQM1 models, CQM1H has achieved a doubled increase in I/O capacity, program capacity, and data memory, and introduced Controller Link distributed control network, protocol macro communication, and various high-speed counting and pulse output functions. For engineers facing maintenance of old equipment, system upgrades, or selection of new projects, a deep understanding of the hardware architecture and core technical characteristics of CQM1H is key to ensuring stable equipment operation and improving control efficiency.

System Overview: Breakthrough in Baseless Modular Design

One of the most prominent features of the CQM1H series is its baseboard free structure - each unit is directly spliced through parallel bus connectors on the side, without the need for a backplane. This design not only reduces the overall height of the system, but also allows users to flexibly configure the number of units according to actual needs, maximizing the use of control cabinet space.

The system consists of the following core components:

CPU unit: Built in 16 point DC input, providing program and data storage, and supporting Inner Board expansion.

Power supply unit: Optional AC (100-240V or 110/230V) or DC (24V), some models provide 24V DC service power supply.

I/O unit: including DC/AC input unit, relay/transistor/three terminal bidirectional thyristor output unit, with points ranging from 8 to 32.

Specialized I/O units: such as analog I/O, temperature control unit, B7A interface unit, safety relay unit, etc.

Communication units: Controller Link unit, DeviceNet I/O link unit, PROFIBUS-DP I/O link unit, CompoBus/S master station unit, AS Interface master station unit.

Plug in board: Installed in two slots inside the CPU unit, it provides high-speed counting, pulse I/O, absolute encoder interface, analog settings, analog I/O, and serial communication functions.

Memory cartridge: Optional EEPROM, EPROM, or Flash memory for program and data backup.

The maximum number of I/O points in the entire system can reach 512 (CPU 51/61), with a maximum program capacity of 15.2K words, data memory (DM) of 6K words, and extended data memory (EM) of 6K words (only CPU 61). Compared to CQM1, the doubling of these capacities provides ample margin for handling increasingly complex control logic and data storage.

CPU Unit Selection: The Core Decision of Performance Grading

CQM1H offers four types of CPU unit models, and engineers need to choose according to application requirements:

Model I/O Capacity Program Capacity DM Capacity EM Capacity Plug in Board Supports Controller Link Supports Built in RS-232C

CQM1H-CPU 11 256 dots, 3.2K characters, 3K characters, all without support, unsupported, unsupported

CQM1H-CPU 21 256 dots, 3.2K characters, 3K characters are all supported. Not supported

CQM1H-CP51 512 points 7.2K words 6K words unsupported (2) supported (1) available

CQM1H-CPU61 512 dots, 15.2K characters, 6K characters, 6K characters support (2), support (1)

Selection suggestion:

For simple single machine control (with fewer than 256 points and smaller program size), CPU 11/21 is sufficient, but please note that CPU 11 does not have an RS-232C port.

If you need to connect to a touch screen, host computer, or perform serial communication, at least select CPU 21.

When high-speed counting, pulse output, analog or protocol macro communication are required, CPU 51/61 must be selected to support the plug-in board.

For applications that require networked distributed control or large-scale data storage, CPU61 is the best choice.

The front of the CPU unit is equipped with DIP switches, and the 8th pin (AR0712) can be customized by the user to distinguish between trial run and formal run modes in the program. In addition, the battery (CPM2A-BAT01) has a lifespan of approximately 5 years in a 25 ° C environment, and replacement should be completed within 5 minutes to prevent memory data loss.

Detailed explanation of plug-in board: the core weapon that endows PLC with dedicated functions

The plug-in board is an important feature that distinguishes CQM1H from other PLCs of the same period. The CPU 51/61 provides two slots (left slot and right slot) inside the CPU unit, which can accommodate the following six types of internal plug-in boards to achieve dedicated functions without occupying external I/O slots.

1. High speed counting board (CQM1H-CTB41)

Applicable slot: left or right slot (can hold two pieces)

Core function: 4-channel pulse input, maximum counting frequency 500kHz (optional 25kHz/250kHz). Supports differential phase (× 1/× 2/× 4), up/down mode, and pulse+direction mode.

Counting range: Linear mode -8388608 to+8388607 (BCD) or hexadecimal; Circular mode 0 to 8388607.

Output: External output of 4-point transistor, capable of outputting 4-bit bit patterns based on target value comparison or region comparison results.