PLCs - Programmable Logic Controllers

PLC stands for Programmable Logic Controller. It is a digital computer-based control system commonly used in industrial automation to monitor and control machinery or processes. A PLC is designed to withstand harsh industrial environments and is typically used to automate tasks that require precision, reliability, and flexibility. It consists of a programmable microprocessor, input and output modules, and various communication interfaces. Typically housed in durable electrical boxes to protect from environmental hazards, PLCs are usually installed near the systems they manage to ensure efficient operation and swift response. This setup helps maintain continuity and safety in industrial applications, making PLCs essential for modern manufacturing and process control.

RS Australia is an online supplier and distributor of industrial PLC controllers with fast delivery. Our stock includes certified models in compact and modular architectures from trusted automation brands like Siemens, Schneider Electric, Omron, and many more.

Types of PLCs

RS Australia stocks both fixed and modular PLC architectures, allowing engineering and procurement teams to select the optimal controller based on current I/O count, future expansion needs, panel space, and site communication protocols:

Fixed/Integrated/Compact PLCs

Often referred to as Fixed I/O PLCs, these controllers have both input and output sections integrated directly into the microcontroller. This integration means that the types and quantities of inputs and outputs are predetermined by the manufacturer and cannot be expanded. These PLCs are small and ideal for applications where the control system does not require customisation or future expansion.

Modular PLCs

Contrasting with fixed PLCs, Modular PLCs offer flexibility and expandability through additional modules. This type allows for expansion in terms of I/O units and other functionalities, making it adaptable to complex systems and changing needs. Each component, including the power supply, communications, and I/O modules, is separate and must be connected to form the complete system. Modular PLCs often include rack-mounted options, where all connections are centralised within the rack, enhancing the system's organisation and scalability.

Standards, Approvals and Authorised Distribution

RS Australia is an authorised distributor for all its programmable logic controller brands, guaranteeing buyers genuine products directly backed by full manufacturer warranties. To support project submissions and validation in regulated or audited environments, such as pharmaceutical, food, and water utility installations, RS provides complete batch and source documentation alongside full certification for regulatory compliance:

• IEC 61131: Standardises industrial PLC architectures and programming languages (IEC 61131-3), ensuring consistent behavior across ladder logic, structured text, and function block diagrams.
• RCM Mark: Mandates regulatory compliance for all electrical equipment supplied directly into Australian and New Zealand markets.
• CE & UL Marks: Certifies electrical safety, structural integrity, and electromagnetic compatibility for global industrial deployment.

Firmware Compatibility and Legacy PLC Replacement

For maintenance engineers and system integrators, verifying firmware compatibility before purchasing a replacement PLC controller is critical. Ordering solely based on parts numbers is risky as a PLC running a newer firmware version may reject an existing project file or alter system behaviour following a mandatory software conversion.

To prevent unnecessary downtime, confirm three key specifications against the product datasheet when sourcing for programmable PLCs on RS Australia.

• Firmware Revision: Confirm the replacement unit matches the firmware version of your installed hardware.
• Software Compatibility: Verify that the replacement supports the exact version of your existing programming software.
• Project File Integrity: Ensure your current project file can download directly to the controller without forcing a conversion.

When a legacy industrial PLC is obsolete, it is recommended to upgrade to the manufacturer's current-generation equivalent. This transition involves converting the project code within the updated programming software, re-verifying I/O addressing, re-testing safety circuits, and accounting for hardware changes, such as upgrading legacy serial links to industrial Ethernet.

Industrial Applications of PLCs

RS Australia supplies industrial-grade PLC controllers to the sectors that power Australian industry, where harsh operating environments and high-reliability demands shape hardware specifications:

• Mining, Extraction & Heavy Processing: Deploys ruggedised PLC controllers built to withstand extreme ambient temperatures, severe vibration from crushing and conveying plants, and abrasive dust. Specifications prioritise conformal-coated electronics, IP-rated enclosures, and remote I/O capabilities for long-distance control room communication.
• Water & Wastewater Treatment: Controls pump duty cycling, level monitoring, flow regulation, and chemical dosing across scattered pump stations, seamlessly integrating remote telemetry links into central SCADA supervision systems.
• General & Advanced Manufacturing: Automates complex assembly lines and high-speed machinery to streamline throughput, optimize production cycles, and uphold stringent quality control standards.
• Power Generation & Energy Distribution: Monitors electrical substations and power distribution networks to balance grid loads, manage circuit breakers, and integrate renewable energy sources.
• Chemical & Petrochemical Processing: Manages precise mixing, chemical reaction timing, and batch processing under strict safety and environmental compliance frameworks.
• Food, Beverage & Packaging: Regulates processing equipment, automated bottling runs, and packaging machinery while maintaining strict product consistency through precise thermal and speed control.
• Pharmaceuticals & Life Sciences: Enforces strict environmental monitoring and precise ingredient blending to ensure full regulatory compliance across critical drug manufacturing processes.

Ordering PLCs From RS Australia

RS is an authorised supplier and distributor of programmable logic controllers in Australia, stocking compact units for standalone machines and modular architectures for plant-wide control. These come from world-leading automation brands including Siemens, Omron, Eaton and many more, so every controller ships as genuine stock under full manufacturer warranty. Product pages list digital and analogue I/O capacities, operating voltages, native communication protocols and supported software revisions, so I/O count and signal type can be matched before a requisition is raised. Orders can be placed online or by phone, email and fax, with bulk and project orders accommodated at special volume pricing quoted on request.

Procurement teams can bundle controllers with complementary hardware in a single order, including HMI displays, PLC power supplies and PLC accessories, making RS a one-stop procurement source for a complete automation build.

Delivery Information for Australia

RS delivers programmable logic controllers Australia-wide. Online orders over $60 (excluding GST) are free on a business account, and locally stocked items ordered before 5pm AEST are delivered the next working day.

Delivery Charges on Online Orders

• Business Accounts (with a valid ABN or an RS credit account):
  • Delivery is free on orders over $60 (excluding GST)
  • A $10 delivery charge applies to orders under $60 (excluding GST)
• Private and Guest Accounts:
  • Delivery is free on orders over $80 (excluding GST)
  • A $20 delivery charge applies to orders under $80 (excluding GST)

Next Working Day Delivery

• Order locally stocked items before 5pm AEST, Monday to Friday
• Orders placed after 5pm Friday arrive Tuesday

Order cut-off times, exclusions and fees are listed in full on the RS Australia delivery page.