PLC programming in Australia

A programmable logic controller (PLC) is an industrial computer that reads inputs from switches and sensors, runs a stored program, and switches outputs such as motors, valves and indicators to control a machine or process. This page sets out what a business commissioning automation, or a person entering the field, typically works through in Australia: the programming languages defined in IEC 61131-3, the stages of an automation project from functional specification to maintenance, work health and safety duties for plant and machine guarding, functional safety, who may do electrical work in each state and territory, cyber security of operational technology, engaging a contractor, and nationally recognised training, with links to official Australian sources.

This is a free, non-commercial reference page. It is general information only, not engineering, legal, electrical safety, work health and safety or cyber security advice, and it does not take into account your circumstances. It does not review, rank or recommend any PLC or automation hardware, software, integrator, contractor or training provider. For advice on your own plant and obligations, speak to a suitably qualified professional and check the official guidance linked below. This page is not affiliated with any business or government body, and listing is not an endorsement.

The guide

The topics most businesses and newcomers work through, in roughly the order an automation project runs.

What a PLC is and the IEC 61131-3 languages

A PLC is a ruggedised controller built for factory and process environments. It repeatedly reads its inputs, executes its program and updates its outputs, and it is usually connected to operator panels, drives, instruments and supervisory systems. The international standard IEC 61131-3, "Programmable controllers – Part 3: Programming languages", defines common programming languages so that skills and code structure carry across different makes of controller. The IEC's summary of the current edition lists the textual language structured text (ST), the graphical languages ladder diagram (LD) and function block diagram (FBD), and sequential function chart (SFC), a set of graphical and equivalent textual elements used to organise programs into steps and transitions. Ladder diagram resembles electrical relay drawings and is widely used for discrete logic; structured text suits calculations and data handling; function block diagrams suit continuous control; and sequential function charts suit machines that move through defined stages.

Write a functional specification first

Before any hardware is bought or code written, describe in plain words what the machine or process must do: each mode of operation (automatic, manual, maintenance), the sequence of operations, alarms and what should happen on each, interlocks, operator screens, data to be recorded, and how the system must behave on power loss, faults and emergency stops. The specification should reflect the plant's risk assessment so that the safety functions are defined up front rather than added later. A clear specification is what testing is measured against, what a contractor quotes against, and what the next person to maintain the system will rely on.

Select the hardware

Hardware selection follows from the specification: the number and type of inputs and outputs (digital, analogue, high-speed), the processing and memory needed, the communications to drives, instruments and other systems, the operator interface, the environment (temperature, dust, moisture, vibration) and the long-term availability of spares and support. Safety functions may need safety-rated controllers or relays rather than standard ones. Safe Work Australia's Guide for safe design of plant says control circuits should be designed to the category, performance level or safety integrity level set by a risk assessment. Allow spare I/O and capacity for future changes.

Programming

Good PLC programs are structured so another competent person can read them: a consistent layout, meaningful tag names, comments, reusable function blocks, and alarm and fault handling designed in rather than patched on. Keep safety functions separate and simple, and do not rely on ordinary program logic for things the risk assessment says need a safety-rated function. Use version control or, at minimum, dated and labelled backups, and record every change. The nationally recognised unit UEEIC0013 lists standard methods trainees are expected to use, such as timers, counters, shift registers and step sequencing, and requires that the control system and program be documented.

Testing: simulation, FAT and SAT

Testing usually happens in stages. Programs can be simulated or bench tested before they reach the site. A factory acceptance test (FAT) checks the control system against the functional specification before it is shipped, often with the customer present. A site acceptance test (SAT) checks it again once installed and connected to the real plant. Each test should follow a written procedure that covers every input and output, every sequence and mode, alarms, interlocks and safety functions, with results recorded and faults fixed and retested. For presence-sensing safeguarding, Safe Work Australia's guidance says safety integrity testing should be carried out to check the safety function works as intended.

Commissioning, documentation and maintenance

Commissioning brings the system into service on the live plant, which means hazardous energy, moving parts and people working close together. Safe Work Australia's model Code of Practice on managing the risks of plant notes that it also applies to those who install and commission plant, and describes lock-out as "the most effective isolation procedure", adding that "A tag should not be used on its own as an isolation device." At handover, the owner should receive current program files (source code with comments, not only compiled files), electrical drawings, I/O lists, network details, the functional specification as built, test records, operating and maintenance instructions, and a list of passwords and licences. Afterwards, keep a backup of the running program, control changes through a documented approval process, and review whether safety functions still work after any modification.

WHS duties for plant and machine guarding

Under the model work health and safety (WHS) laws, designers, manufacturers, importers, suppliers, installers and the business that manages or controls plant each have duties. Safe Work Australia's guide says "A designer must ensure, so far as is reasonably practicable, plant is designed without risks to health and safety", and its information sheet notes that anyone who modifies plant becomes its designer if someone else did not design the modification, which can include changing its control system. The model Code of Practice sets out the hierarchy of control and, following the regulations, an order of preference for guarding: a permanently fixed barrier, then an interlocked physical barrier, then a barrier removable only with a tool, then a presence-sensing safeguarding system. Emergency stops must be prominent and immediately accessible, but the guidance says they "should not be the only method of controlling risks." Check with your state or territory WHS regulator which laws and codes apply to you.

Functional safety in general terms

Functional safety is about making sure that safety functions carried out by control systems, such as stopping a machine when a guard is opened or a light curtain is broken, work reliably when needed, including when components fail. Safe Work Australia's guidance ties the design of these functions to the plant's risk assessment and says "Software used for safety functions should be referenced against the relevant Australian Standards." The model Code of Practice lists relevant standards including the AS 4024 series (safety of machinery), AS 62061 (functional safety of safety-related electrical, electronic and programmable electronic control systems) and AS 61508 (functional safety of safety related systems). It also says the emergency stop must not be adversely affected by electrical or electronic circuit malfunction. Functional safety design and verification is specialist work; ask anyone doing it what methods and standards they apply and how they document the result.

Electrical licensing: who may do the wiring

PLC programming itself is not licensed, but electrical wiring and installation work is, and in every state and territory checked it must be done by appropriately licensed or registered electrical workers, with a contractor licence or registration needed to do it for others as a business. In NSW the government says "You must have an electrical licence before undertaking any electrical wiring work in NSW". In Victoria, Energy Safe Victoria licenses electrical workers and installation work must be carried out through a registered electrical contractor. In Queensland, the Electrical Safety Office says "A person who performs electrical work in Queensland must have an electrical work licence authorising the work." In South Australia, Consumer and Business Services administers electrical worker registration and contractor licensing. In Western Australia, "Only licensed electricians can do electrical installation work." In Tasmania an electrical practitioner licence is needed, and in the Northern Territory licensing sits with the Electrical Safety Regulator within NT WorkSafe. A programmer who is not licensed should not terminate, alter or disconnect wiring, even on control circuits.

Cyber security of operational technology

PLCs are part of operational technology (OT): systems that monitor and control physical equipment. Connecting them to business networks, the internet or vendors' remote access tools brings cyber risk to physical processes. The Australian Signals Directorate's Australian Cyber Security Centre (ACSC) and international partners publish Principles of operational technology cyber security, which sets out six principles: "Safety is paramount"; "Knowledge of the business is crucial"; "OT data is extremely valuable and needs to be protected"; "Segment and segregate OT from all other networks"; "The supply chain must be secure"; and "People are essential for OT cyber security". Related guidance on keeping a definitive view of OT architecture says organisations "should aim to create a definitive record of all OT systems that it owns and operates", including what each asset connects to and any vendor remote access. The ACSC's Secure connectivity principles for OT cover reducing unnecessary exposure, limiting the impact of a compromise, monitoring connections and planning to isolate systems.

Engaging a contractor or integrator

Agree the scope in writing, ideally as a functional specification, along with the deliverables, the tests that define completion, the documentation to be handed over, and who is responsible for safety design, electrical work and remote access. Settle ownership of the program. business.gov.au says that if your business should own the IP a contractor creates, the contract must say so, "Otherwise, the contractor will own the IP of any work they create during the contract period", and IP Australia suggests contracts cover who owns and may use the IP, when ownership transfers, changes and improvements, confidentiality and returning copies. Ask for unlocked, commented source code, not just a compiled program. Agree defects and support periods in writing. Under the Australian Consumer Law, the ACCC says a business buying for business use can be covered by consumer guarantees in some cases, including where the purchase "costs less than $100,000 including GST", though purchases for production or manufacturing are excluded; the guarantees for services include due care and skill and delivery within a reasonable time. Get professional advice on contracts for larger projects.

Training pathways

Nationally recognised training in PLC programming sits mainly in the electrotechnology (UEE) training package on training.gov.au. Units include UEEIC0013 "Develop, enter and verify discrete control programs for programmable controllers", UEEIC0014 "Develop, enter and verify programs in supervisory control and data acquisition systems" and UEEIC0015 "Develop, enter and verify word and analogue control programs for programmable logic controllers". These appear in UEE42220 Certificate IV in Instrumentation and Control, which training.gov.au describes as covering competencies to "select, install, set up, test, fault find, repair, maintain and commission" measurement and process control systems. Training.gov.au states that no licensing requirements apply to that qualification or to UEEIC0015 at the time of publication, so completing them does not by itself allow a person to do licensed electrical work. Engineers Australia operates the National Engineering Register for engineers assessed against competency standards for their occupational category.

Directory

Official Australian sources on plant safety, electrical licensing, OT cyber security, contracts and IP, training and professional registration, instead of a list of vendors, integrators or training providers. Each entry was checked against its own official website.

What is listed. Only government bodies and one professional body are included, and only where the page could be fetched and checked. Each link goes to that body's own page. The list is not complete and is in no particular order. No PLC makers, software vendors, system integrators, contractors or training providers are listed.

Not an endorsement. Listing is not a recommendation. This page is not affiliated with any organisation below and does not review, rank or recommend any product, service or provider.

Inclusion in this directory is not an endorsement. Links are to official websites as published at the time of checking.

Questions to ask before starting an automation project

Plain questions worth answering internally, and putting to any programmer, integrator or contractor, before work starts.

Do we have a written functional specification?

It is what the work is quoted, built and tested against. Without it, disputes about what was promised are hard to resolve.

Has the risk assessment identified which safety functions are needed?

Safety functions should be designed to the category, performance level or safety integrity level the risk assessment calls for, not left to ordinary program logic.

Who is the designer if we modify existing plant?

Safe Work Australia notes that a person who modifies plant can become its designer, with the duties that come with that role.

Who will do the electrical work, and are they licensed in this state?

Wiring and installation must be done by appropriately licensed or registered electrical workers. Check licences with the state or territory regulator.

Who will own the program, and will we get unlocked source code?

A contractor owns what it creates unless the contract says otherwise. Without editable, commented source code, future changes may depend on the original programmer.

How will the system be tested and accepted?

Agree written FAT and SAT procedures that cover every input, output, sequence, alarm, interlock and safety function, and how faults found are fixed and retested.

How is remote access and network connection controlled?

The ACSC's OT principles call for segmenting OT from other networks and securing the supply chain, including vendor remote access.

What documentation will we receive at handover?

Program files, drawings, I/O lists, network details, test records and manuals let others maintain the system safely.

What support and defect period is agreed?

Put response times, defect periods and support costs in writing, alongside any rights you have under the Australian Consumer Law.

About this page

plcprogramming.com.au is a free, non-commercial reference page published by Radiant Life Distributors Pty Ltd, Adelaide. It is general information only, not engineering, legal, electrical safety, work health and safety or cyber security advice. It sells nothing, does not review, rank or recommend any PLC hardware, software, integrator, contractor or training provider, and makes no claims about results. It is not affiliated with, or endorsed by, any organisation listed; listing is not an endorsement. Information was checked against official websites in October 2026; law and guidance change, so confirm current details with the organisations linked above.