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.

Typical applications: Multi axis position detection, encoder high-speed counting, fixed length cutting control.

2. Pulse I/O board (CQM1H-PLB21)

Applicable slot: Right slot only

Pulse input: 2 channels, single-phase up to 50kHz, differential phase 25kHz. Support target value/region comparison interruption.

Pulse output: 2 channels, up to 50kHz (20kHz when connected to a stepper motor). Supports trapezoidal acceleration and deceleration control with fixed duty cycle (50%) (using PULS/PED commands) and variable duty cycle (1% -99%, using PWM commands).

Typical applications: stepper motor positioning control, proportional solenoid valve drive, frequency adjustable PWM heating control.

3. Absolute Encoder Interface Board (CQM1H-ABB21)

Applicable slot: Right slot only

Core function: 2-channel absolute encoder input (binary Gray code, maximum counting frequency 4kHz), resolution 8/10/12 bits optional. Support origin compensation (set to zero at any position) and power-off to maintain position data.

Interruption: Target value comparison (48 points) or region comparison (8 intervals).

Typical applications: Absolute position detection of rotating workbenches, height positioning of lifting equipment.

4. Simulation setting board (CQM1H-AVB41)

Applicable slot: left or right slot (but not both at the same time)

Core function: 4 multi turn potentiometers, with set values stored in IR 220 to IR 223 using 4-digit BCD codes (0000-0200).

Typical application: Operators manually adjust timer settings, speed settings, and PID target values without the need for programming equipment.

5. Analog I/O board (CQM1H-MAB42)

Applicable slot: Right slot only

Input: 4-channel, can independently select -10~+10V, 0~10V, 0~5V or 0-20mA, resolution 1/4096, A/D conversion time 1.7ms/point.

Output: 2 channels, can independently select -10~+10V or 0-20mA, D/A conversion time is 1.7ms/2 points.

Accuracy: ± 0.5% FS at 25 ° C, ± 1.0% FS at 0-55 ° C.

Note: There is no hardware averaging function, and if filtering is required, the AVG instruction in the program must be used.

Typical applications: analog sensor acquisition, frequency converter speed setting, servo torque command.

6. Serial Communication Board (CQM1H-SCB41)

Applicable slot: only left slot

Port: 1 RS-232C (maximum 19.2kbps, 15m), 1 RS-422A/485 (maximum 19.2kbps, 500m, supports 1: N connection).

Protocol support: Host Link, no protocol, protocol macro, 1:1 data link, NT link (1:1 or 1: N).

Protocol macros: Allow users to create custom communication protocols using CX Protocol software, exchange data with serial devices such as thermostats, barcode scanners, and smart meters, and execute them in single steps through PMCR instructions.

Typical applications: Communicating with multiple frequency converters, connecting touch screens (NT Link), and reading third-party instrument data.

I/O unit and communication unit: the cornerstone of building a complete control system

1. I/O unit

Input unit: DC input (12V/24V, 8/16/32 points), AC input (100-120V or 200-240V, 8 points). The response time can be set to 1-128ms in the PLC setup.

Output unit: Relay output (2A/point, 8/16 points), transistor output (NPN or PNP, 0.1A-2A), three terminal bidirectional thyristor output (0.4A).

Specialized I/O units: B7A interface unit (single cable up to 500m), temperature control unit (thermocouple/platinum resistor, 2/4 circuits, with heater disconnection alarm), safety relay unit (2 safety inputs+4 general inputs), analog input/output unit (CQM1-AD042/DA022), etc.

2. Communication unit

Controller Link Unit (CQM1H-CLK21): Supports data linking (automatic data sharing, maximum 1000 word transmission/8000 word reception per node) and information services (SEND/RECV/CMND instructions). Transmission distance: 500m at 2Mbps, 800m at 1Mbps, 1km at 500kbps. Up to 32 nodes. Suitable for multi PLC data exchange in production lines.

DeviceNet I/O Link Unit (CQM1-DRT21): DeviceNet slave station, 16 inputs/16 outputs, occupying 1 input word+1 output word. Supports 125/250/500kbps, with a maximum communication distance of 500m (125kbps).

PROFIBUS-DP I/O Link Unit (CQM1-PRT21): Slave, configurable 2/4/6/8 word I/O, automatically detects 9.6k-12Mbps baud rates, addresses 0-99. Support DP functions such as Sync/Freeze/Clear.

CompoBus/S Master Station Unit (CQM1-SRM21-V1): Supports high-speed mode (750kbps, 100m) and long-distance mode (93.75kbps, 500m). The number of I/O points can be set to 128 points (64 in/64 out), 64 points, or 32 points, with 4 or 8 points per slave station. The fastest communication cycle is 0.5ms.

AS Interface Master Station Unit (CQM1-ARM21): controls up to 31 slave stations, with 4 inputs and 4 outputs per slave station, and a communication cycle of 5ms.

Advanced features: interrupts, high-speed counting, and pulse output

CQM1H provides multiple interrupt handling mechanisms, significantly improving real-time response capabilities:

1. Input interrupt

The four points of IR 00000~IR 00003 built into the CPU unit can be used as interrupt inputs. After being enabled by the INT (89) instruction, when the input signal changes from OFF to ON, the main program pauses and immediately executes the corresponding interrupt subroutine (subroutine number 00-03). The interrupt response time is not affected by the PLC scanning cycle and is suitable for emergency parking, high-speed detection, and other scenarios.

2. Interval timer interrupt

The STIM (69) instruction can be used to set up to 3 interval timers to trigger interrupt subroutines with a fixed cycle (minimum 0.5ms). Suitable for tasks that require periodic execution, such as PID calculations and data acquisition, to avoid jitter caused by changes in scanning cycles.

3. High speed counter interrupt

The CPU unit has a built-in high-speed counter (using three input points IN04, IN05, and IN06) that can count pulses from the rotary encoder, with a maximum frequency of 5kHz for single-phase and 2.5kHz for two-phase. Support target value comparison (up to 16 target values) and region comparison (up to 8 intervals), and execute interrupt subroutine when the count value reaches the condition.

The pulse I/O board (PLB21) and high-speed counting board (CTB41) provide faster counting and richer interrupt configurations (up to 48 target values).

4. Pulse output

Fixed duty cycle pulse: Use PULS (65) command to set the number of pulses (1 to 16777215), SPED (64) command to set the frequency (10Hz-50kHz), which can be combined with ACC command to achieve trapezoidal acceleration and deceleration.

Variable duty cycle pulse: Use PWM commands to output pulses with a duty cycle of 1% -99%, fixed frequency (91.6Hz, 1.5kHz, 5.9kHz), suitable for proportional control.

Programming and Debugging: CX Programmer and Protocol Macros

CQM1H supports OMRON CX Programmer software (Windows platform), which can be programmed and monitored through peripheral ports (connected to programming consoles or computers) or RS-232C ports.

Programming language: ladder diagram, with 162 instructions (14 basic instructions and 148 special instructions). The basic instruction execution time is 0.375-1.125 μ s, and the MOV instruction is 17.7 μ s.

Online editing: In MONITOR mode, user programs can be overwritten on a block by block basis, supporting simultaneous editing of multiple blocks.

Memory cartridge: It can store user programs, PLC Setup, and other data in EEPROM/EPROM/Flash. Simply replace the cartridge and restart to switch the entire software configuration, suitable for quick changeover in multi variety production.

Protocol macro development: Use CX Protocol software to create or modify communication protocols, download them to the serial communication board (SCB41), and call them using PMCR instructions in the ladder diagram. The system has built-in standard protocol libraries for communication with OMRON thermostats, barcode readers, modems, and other devices.

Key points of fault diagnosis and maintenance

1. Error log

CQM1H can record up to 10 errors (including user-defined errors), including error codes, details, and occurrence times (using a memory cartridge with a clock). Error logs can be read through programming devices.

2. Common errors and countermeasures

I/O verification error: The actual installed unit does not match the configuration recognized by the system. CQM1H does not have an I/O table, but if a bus error or unit recognition occurs, it is necessary to check the unit connection sequence and power load.

Cycle Time Over Flag (SR area) ON and operation continues when the cycle time exceeds 100ms; If the set cycle monitoring time (0-990ms/10ms step or 0-99s/1s step) is exceeded, the CPU will stop running. The SCAN instruction can be used to set the minimum cycle time.

Battery error: An alarm is triggered when the battery voltage is low, and it needs to be replaced as soon as possible. The replacement time should not exceed 5 minutes.

FAL/FALS Error: The user program can use FAL (06) to generate non fatal errors (flashing ALARM), FALS (07) to generate fatal errors (stopping PLC), and output custom error codes.

3. Maintenance operations

I/O Hold: If SR 25212 (I/O Hold Bit) is set to ON and this bit is held when the power is set to ON in the PLC Setup, the contents of the IR and LR areas will still be retained after mode switching or power failure.

Output OFF: When SR 25215 (Output OFF Bit) is set to ON, the outputs of all output units are forcibly cut off for emergency stop.

Force Set/Reset: The programming device can force ON/OFF to any position, supporting differential monitoring and data tracking.

Summary and Selection Guide

As the pinnacle of the OMRON CQM series, CQM1H's baseless modular design, dual plug-in board expansion, high-speed network interconnection, and rich specialized functions make it an ideal choice for single machine control to distributed systems.

Quick selection checklist:

Recommended configuration for application requirements

Small point logic control (<256 points) CQM1H-CPU11/21+power supply+I/O unit

RS-232C communication or touch screen CQM1H-CPU 21 or above is required

High speed counting (encoder) CPU 51/61+CTB41 or PLB21 (depending on frequency)

Stepper/servo pulse control CPU 51/61+PLB21

Analog input/output CPU 51/61+MAB42 (4 inputs/2 outputs) or AD042/DA022

Serial communication with third-party devices CPU 51/61+SCB41 (protocol macro)

Multi PLC data sharing CPU 51/61+CLK21 (Controller Link)

Distributed I/O (low-cost) with any CPU+SRM21-V1 (CompoBus/S)

Fieldbus/DeviceNet integration corresponds to slave units

In terms of spare parts, CQM1H has gradually ceased production, but there are still a large number of devices in operation. It is recommended that users keep CPU units, power supply units, and commonly used I/O units, and regularly backup programs to memory cartridges. For communication faults, prioritize checking the bus terminal resistance setting and baud rate matching; For abnormal pulse output, confirm whether the external power supply capacity and load resistance meet the requirements.