MITSUBISHI ELECTRIC MELSEC iQ-R/Q/L Complete Guide

System Q Series: Mature and Reliable Modular Main Force

3.1 Universal CPU and High Performance Models

The System Q series offers over 25 general-purpose CPU models, ranging from Q00UCPU (10k steps, 120ns/step) to Q100UDEH (1000k steps, 9.5ns/step). The QnUDV series (such as Q03UDV and Q26UDV) uses high-speed RISC processors, with LD instructions requiring only 1.9ns, and supports SD cards and extended SRAM cartridges.

Multi CPU system: System Q can install up to 4 CPUs (PLC, motion, PC, C controller, robot, or NC CPU) on the same substrate. For example, combining a general-purpose CPU with a Q172DSCPU motion CPU to achieve the separation of sequential control and high-speed motion control. When allocating I/O modules, each CPU has an independent I/O range (divided by the "CPU No." switch on the substrate).

Fault case: In a multi CPU system, one CPU cannot access the I/O module. The common reason is that the "control CPU" is not set correctly in the I/O allocation parameters. In the "PLC Parameters" ->"I/O Allocation" section of GX Works2, specify the CPU number to which each module belongs (main CPU is 0, others are 1-3). If the module is shared by multiple CPUs, "shared memory" communication needs to be enabled.

3.2 Redundant CPU and Hot Backup System

Q12PRHCPU and Q25PRHCPU support hot standby redundancy, and the primary and backup systems synchronize data through fiber optic tracking cables (QC10TR/QC30TR). The minimum user configurable switching time is 22ms (48k word synchronous data). The redundant system can connect to remote I/O stations (via MELSECNET/H redundant ring network), but the central expansion board cannot be used.

Replacement precautions: If upgrading an old Q series non redundant system with Q12PRHCPU, it is necessary to replace it with a redundant substrate (such as Q38RB) and add a backup power module (Q63RP). The original program can be used directly, but redundant parameters such as tracking data capacity and switching conditions need to be added.

3.3 Security Solution: QS and WS

QS Safety PLC (QS001CPU): an independent safety controller that complies with SIL3/Cat.4 and is connected to remote safety I/O via CC Link Safety network (such as QS063BT82-12DT). Suitable for the safety protection of the entire production line.

Safety relay module (QS0RS2SN, etc.): can be directly installed on standard Q series substrates to add safety functions to conventional PLCs without the need for an independent safety controller.

WS Security Controller (WS0-CPU0002): A compact security controller programmed through graphical functional blocks, suitable for standalone or small systems.

Fault handling: The safety relay module reports an error of "input inconsistency". Check if the dual channel safety inputs (such as the two normally closed contacts of the emergency stop button) are activated simultaneously. Use a multimeter to measure the resistance difference between two channels. If the difference is greater than 50 Ω, it may be due to contact oxidation or poor circuit contact. Replace the button or re press the terminal.

L series: compact high-performance choice without bottom plate

4.1 Clever design of built-in functions

The L series CPUs (L02CPU, L26CPU-BT, etc.) adopt a baseless structure and directly expand modules through side connectors, saving a lot of cabinet space. Each CPU comes with:

24 point digital I/O (16 in/8 out), with 2 channels supporting 200kHz high-speed counting and 200kHz pulse output (can be used to control two axis servo or stepper).

Built in USB Mini-B and Ethernet (10/100M) ports, supporting direct programming and SLMP communication.

SD/SDHC card slot for data recording (up to 10 settings, 32-4832kB each).

The high-end version (L26CPU-BT) has an additional built-in CC Link master/slave function (up to 10Mbps).

Application tip: Use the built-in data recording function to collect device operating parameters (such as temperature, pressure, and output) without the need to write complex programs. Set the sampling trigger conditions and storage format through the "Data Record Configuration" wizard of GX Works2. The generated CSV file can be directly analyzed using Excel for easy fault tracing.

4.2 Scalability

The L series can connect up to 40 expansion modules (main module+expansion module). By using L6EXB branch modules and L6EXE extension modules, flexible module layout can be achieved. The longest extension cable is 30 meters (LC30E), suitable for layered installation of control cabinets.

Troubleshooting: All LEDs of the expansion module are off, but the CPU is normal. Firstly, check if the expansion cable is securely plugged in, and then measure the 5V power supply (from the CPU side) on the expansion module. If the voltage is lower than 4.75V, it indicates that the CPU power supply capacity is insufficient and a higher power module needs to be replaced (L61P outputs 5A, while L63P outputs only 0.6A? In fact, L61P is 5A and L63P is 24V input, and the output capacity needs to be checked in the table. More accurate: L61P outputs 5V 5A, L63P outputs 24V, outputs 5V 2.5A? According to the PDF, L63SP outputs 5V 2.5A. Users should be prompted to calculate the total load current.