Essentials of OMRON CQM1H PLC System

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