Modular PLC System | Products — SGT Systems Limited

Overview

Modular PLC System is a DIN-rail Programmable Logic Controller built for industrial machine logic: a deterministic CPU plus a snap-together stack of digital, analog, high-speed counter and comms modules. Engineers program in IEC 61131-3 ladder, structured text, function block or SFC; field devices wire straight into spring-cage terminals.

Designed for OEM machine builders, system integrators and plant maintenance teams who need real-time control with deterministic scan cycles, diagnostics, and a path from prototype to production on the same hardware family.

Modular by design — mix DI, DO, AI, AO, HSC, fieldbus modules to match your I/O count
Deterministic scan — 1–10 ms cycle, <0.1 ms jitter
IEC 61131-3 — ladder, structured text, function block, SFC, instruction list
Fieldbus options — Modbus RTU/TCP, Profinet, EtherCAT, EtherNet/IP, OPC UA server

How It Works

CPU module on the leftmost DIN-rail slot reads the I/O backplane bus every scan, runs the user program, and writes outputs at deterministic intervals.
I/O modules snap onto the rail to the right of the CPU; the backplane connector auto-addresses them. Hot-swap supported for field replacement.
Field devices (sensors, valves, motors, drives, encoders, E-stops) wire into spring-cage terminals on the front of each I/O module.
Scan cycle — read inputs → execute logic → write outputs → housekeeping & comms → repeat.
Engineering IDE on a laptop talks to the CPU over Ethernet; engineers download programs, monitor live tags, set breakpoints, force values for commissioning.

Features

5 IEC 61131-3 languages — LD, ST, FBD, SFC, IL in one project
Hot-swap I/O modules — replace a faulty card without powering down
Online edit — modify running logic without stopping the machine
Diagnostics module — per-module health, faults, retries, voltage levels
OPC UA server — exposes tags to SCADA, MES, IT systems out of the box
Redundant CPU option — standby CPU on the same rail with bumpless transfer
Cybersecurity — role-based access, signed firmware, audit log, optional VPN tunnel
Cloud bridge — built-in MQTT client for sending tags to SGT or your own broker

Use Cases

OEM machine builders — bottlers, packers, assemblers, converting lines
Process plants — batching, mixing, dosing, CIP-SIP
Material handling — conveyors, sortation, palletisers, AS/RS
Building & infrastructure — HVAC, pump stations, water treatment, lighting
Energy — substations, solar trackers, BESS controllers, gen-set ATS
Retrofit & modernisation — replace obsolete S5 / S7-200 / SLC-500 / MicroLogix

Specifications

CPU: ARM Cortex-A 1 GHz, 512 MB RAM, 4 GB flash, real-time Linux kernel
Scan cycle: 1–10 ms configurable, <0.1 ms jitter
I/O capacity: Up to 32 modules per rail, up to 4 racks (1024 I/O) per CPU
Module types: 16/32 DI, 16/32 DO (relay/SSR), 4/8/16 AI (V/mA/RTD/TC), 4/8 AO, HSC 100 kHz, COMM
Fieldbus: Modbus RTU/TCP, Profinet IO, EtherCAT master/slave, EtherNet/IP, OPC UA
Compliance: CE, UL 508, IEC 61131-2, IEC 61508 SIL-2 variants, ATEX zone 2
Environmental: −25 to +60°C, IP20 (cabinet-mount), 24 VDC ±20%
Lifecycle: 15-year availability guarantee, 5-year hardware warranty