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12 October 2012

Launched in Japan a year ago and now available worldwide, the MELSEC L series PLC from Mitsubishi Electric has been designed to bridge the gap between the FX compact PLC and the Q series

With functionality exceeding that traditionally associated with mid-range PLCs, the MELSEC L has all the features and functions needed for sophisticated automated machines built into the CPU. Combining the L Series with other Mitsubishi products such as the GOT HMIs and Inverter Drives, offers the machine builder a sophisticated, cost effective, integrated control platform.


Typical applications include high speed bottling, labelling and packaging machines. Features include 24 points of on board I/O, a dual-channel high speed counter, two axes of positioning, pulse catch and interrupt functions, Ethernet connectivity and built-in data logging.




The positioning function has a start time of just 30μs, with a maximum high-speed output of 200k pulses per second, and features such as S-curve acceleration and deceleration, meeting the needs of complex machine positioning applications.


The data logging function provides a simple means of collating OEE (overall equipment efficiency) data, energy monitoring, sequencing and production traceability, with the facility to store this data to an SD memory card using the integral memory card slot. The same memory card slot also makes it easy to back up or load the CPU programs and parameters. The backups can then be just as easily restored or used to program other CPUs. The memory card can also be used to hold data captured with the data logging function. Typical PLC input devices are unable to detect pulse signals whose ON time is shorter than the scan time or do not occur during I/O refresh periods. The pulse catch function allows these signals to be reliably detected and passed to the sequence program. This function is different from the interrupt input function in that it does not require any special programming. Pulse catch inputs may be used in programs exactly the same as traditional input (X) signals.


The Ethernet communications port provides a simple interface to enterprise level, seamless peer-to-peer communications, and direct connectivity to HMIs. Logged data can also be retrieved via this port using FTP commands. The CPU has a basic operation

processing speed of better than 9.5ns per instruction and this makes it ideally suited to high speed machine applications. The base CPU for example, can incorporate a 16-character by 4- line display, providing convenient monitoring and easy access to diagnostic information both for the CPU and any connected I/O modules, without the need to connect a PC or software. Users can check the system status and make setting changes directly from the display.


Key Points

  • Typical applications include high speed bottling, labelling and packaging machines
  • The system can be expanded up to a total of 40 expansion modules, which include motion control modules, analogue I/O modules and temperature control modules

The system can be expanded up to a total of 40 expansion modules, which include motion control modules, analogue I/O modules

and temperature control modules. Mitsubishi Electric has developed a new motion module for the L Series that provides high-speed,

high precision control of up to sixteen axes per module over Mitsubishi’s SSCNET III servo controller network. SSCNET is limited to Mitsi servos but maximises speed in this configuration. The CPU can accommodate multiple motion modules and can consequently provide many axes of control, with capabilities including a cam function, phase compensation, mark detection and 600 points of user-defined positioning data. The high-speed analogue modules have been designed to provide a conversion speed of just

20μs per channel, with a precision of +/-0.1%. Temperature control modules provide highly stable regulation performance.




Interfaces to CC-Link IE Field, CC-Link and Modbus allow access to information across the network. CC-Link is the dominant FA

network standard in Asia and continues to gain support worldwide. L series CPUs are compatible with the latest generation of CC-Link devices and support connections with over 1000 different product types. Without adding a module, these CPUs can perform high-speed communication with a maximum of 128 words between a master station and a local station. CCLink IE Field is an ethernet-based Gigabit network designed to provide cost-effective, reliable connectivity to field devices.