Hitachi LY Series Modules: LYD105A,

Technical Dossier

Product Details And Specifications

Hitachi LY Series: Comprehensive Module Range and Technical Overview

The Hitachi LY Series represents a core family of programmable logic controller (PLC) I/O modules deployed across global heavy industry installations, including petrochemical refineries, nuclear power auxiliary systems, steel manufacturing lines, and offshore platform control architectures. Originally developed as part of Hitachi's HIDIC (Hitachi Distributed Industrial Controller) platform, the LY Series established a standardized backplane bus interface that enabled modular expansion across large-scale distributed control environments. Installations of LY Series hardware remain active in facilities across Japan, Southeast Asia, the Middle East, and Eastern Europe, where long equipment lifecycles of 15–25 years make spare parts availability a critical operational concern.

The Evolution of LY Series Architecture

The LY Series was introduced as part of Hitachi's second-generation HIDIC PLC platform, succeeding the earlier H Series discrete I/O modules. The architecture is built around a parallel backplane bus with fixed slot addressing, supporting both local and remote I/O expansion racks. Early LY modules operated on 5 VDC internal logic with optocoupler-isolated field interfaces, a design retained across subsequent revisions to maintain backward compatibility with existing rack assemblies.

Key architectural milestones include the transition from DIN-rail discrete wiring to terminal block connector standardization (LY-D and LY-A sub-families), the introduction of high-density 32-point modules (LYD132, LYA132) to reduce rack slot consumption, and the later addition of diagnostic LED arrays for per-channel fault indication. Compatibility between early and late LY Series modules is maintained at the backplane level, provided the CPU module firmware version supports the extended module type codes introduced after 1998. Integrators replacing early LYD105A units with later-revision equivalents should verify CPU compatibility tables before substitution.

LY Series Full Catalog & Functionalities (SKU List)

DC Input Modules (DI)

• LYD105A: 16-point 24 VDC sink/source input module, 5 ms filter, screw terminal
• LYD110A: 16-point 12 VDC DC input module, optocoupler isolated, standard density
• LYD132A: 32-point 24 VDC high-density input module, dual connector interface
• LYD205A: 16-point 48 VDC input module, extended voltage range, industrial grade
• LYD305A: 16-point 100–120 VDC input module, high-voltage field interface

AC Input Modules (AI)

• LYA105A: 16-point 100–120 VAC input module, zero-cross detection, screw terminal
• LYA205A: 16-point 200–240 VAC input module, optocoupler isolated, standard density
• LYA132A: 32-point 100–120 VAC high-density input module, dual connector

DC Output Modules (DO)

• LYR105A: 16-point relay output module, 2A per point, Form A contacts, screw terminal
• LYT105A: 16-point transistor sink output, 24 VDC, 0.5A per point, short-circuit protected
• LYT132A: 32-point transistor output, high-density, dual connector, 24 VDC
• LYT205A: 16-point transistor source output, 24 VDC, 0.5A per point

AC Output Modules (AO)

• LYS105A: 16-point triac (SSR) output, 100–240 VAC, 1A per point, zero-cross switching
• LYS205A: 16-point triac output, 200–240 VAC, 2A per point, industrial duty

Power Supply & Specialty Modules

• LYP100: Rack power supply module, 24 VDC input, 5 VDC/3A backplane output
• LYP200: Rack power supply module, 100–240 VAC input, 5 VDC/5A backplane output
• LYC100: Communication adapter module, RS-232C/RS-485, HIDIC network interface

Sourcing Hard-to-Find & Obsolete LY Series Parts

The Hitachi LY Series entered end-of-life status progressively between 2005 and 2015, with Hitachi Industrial Equipment Systems discontinuing active production of most module variants. However, the installed base remains substantial, and facilities operating HIDIC-based control systems require access to verified replacement units to avoid full system migration costs, which typically range from USD 200,000 to over USD 1,000,000 for large-scale DCS replacements.

Quality Control for the LY Series Range

LY Series modules present specific test challenges due to their parallel backplane bus architecture and optocoupler-based field isolation. DriveKNMS applies a structured verification protocol to all LY Series units prior to dispatch:

• Backplane connector inspection: All edge connector pins are inspected under magnification for oxidation, mechanical deformation, and solder joint integrity. Pins are cleaned with isopropyl alcohol and contact conditioner where required.
• Functional I/O verification: Each input channel is stimulated at rated voltage (24 VDC for LYD105A) and the corresponding status LED and internal register bit are verified using a HIDIC-compatible test rack. All 16 channels are tested individually.
• Optocoupler leakage test: Field-side to logic-side isolation resistance is measured at 500 VDC. Minimum acceptable isolation is 10 MΩ per IEC 61131-2 requirements.
• Thermal cycling: Units are cycled between 0°C and 55°C for a minimum of two cycles to identify latent solder joint failures before shipment.
• Firmware/revision documentation: Hardware revision codes are recorded and included with shipment documentation to allow integrators to verify compatibility with installed CPU firmware versions.