Hire a freelance PLC programmer
Post the job, read what engineers propose, and agree terms with someone who works in your controller family. Ingenium is the marketplace and holds the contract; the engineer you hire writes the code.
Post a PLC jobWhat a PLC programmer actually does
A programmable logic controller is the computer that runs a machine or a process line. Programming it means writing the logic that decides what moves, when, and what happens when something goes wrong.
Most plants run one of two controller families, and they are not interchangeable skills. Allen-Bradley hardware, made by Rockwell Automation, is programmed in Studio 5000 Logix Designer on current processors and in RSLogix 500 on the older MicroLogix and SLC range. Siemens hardware is programmed in TIA Portal, or in SIMATIC STEP 7 on S7-300 and S7-400 systems that have not been migrated. The tag models, the instruction sets and the way a project is organised differ enough that an experienced Rockwell programmer is a beginner in TIA Portal for the first week. Name the platform in the job post — it is the single most useful line in it.
The logic itself is written in the IEC 61131-3 languages. Ladder logic still dominates, and for a good reason: a maintenance electrician at three in the morning can read a rung and see which contact is holding the machine up. Structured text is used where ladder stops being readable — recipe handling, arithmetic, string work, loops over arrays — and function block diagram turns up in process control and motion. Real programs mix them, and a programmer worth hiring can explain why each routine is in the language it is in.
Very little of the job is only code. It includes the I/O list and how each point maps to a physical terminal, the interlocks and permissives that stop the machine hurting itself, the alarm bits the operator interface will read, communications down to drives and instruments and up to a SCADA layer, and the recovery routines that let a line restart after a fault instead of needing a power cycle. On a retrofit it starts with reading somebody else’s undocumented program and working out what it was for.
And it finishes on site. Logic that simulates perfectly still has to be commissioned against real sensors, real valve response times and real material, which is where the hours usually go. Decide before you send an offer whether commissioning is inside the scope, because it changes the shape of the engagement more than anything else on the list.
What a PLC job usually covers
Useful either way round: a client can turn this into a job post, and an engineer can price against it.
I/O list and tag naming
Every field device mapped to an address and a tag name, with naming consistent enough that the program, the operator screens, the alarm list and the panel drawings all refer to the same valve by the same word.
Control logic
Sequences, modes, interlocks and permissives — the part that makes the machine do its job. Ladder logic for anything maintenance will have to read on a bad night, structured text where ladder would turn into a wall of rungs.
Faults, alarms and recovery
Hardwired safety circuits are not PLC code, but the controller still has to react to them, latch a fault with a cause the operator can act on, and return to a known state. Safety-rated logic on a GuardLogix or an F-CPU is a separate competence — ask about it explicitly if you need it.
Communications
EtherNet/IP, Profinet, Modbus TCP or serial links out to VFDs, servo drives, instruments, robots, weighers and the supervisory layer. Frequently the part of the project that takes longest to make genuinely reliable.
Documentation and backups
Commented routines, a cross-reference that is not a lie, a current program backup with a revision history, and notes a plant electrician can follow without phoning the author. This is what you are really buying.
Commissioning support
Point-to-point checks, loop testing, dry cycles, then production rate with real material. Often worth separating from the programming so the site schedule does not drag the whole engagement with it.
Platforms, languages and networks
The vocabulary of the trade. Naming the right items in a job post is most of the work of writing one.
Allen-Bradley / Rockwell
- Studio 5000 Logix Designer
- RSLogix 5000
- RSLogix 500
- ControlLogix
- CompactLogix
- MicroLogix
- GuardLogix
- RSLinx
Siemens
- TIA Portal
- SIMATIC STEP 7
- S7-1200
- S7-1500
- S7-300 / S7-400
- SIMATIC Manager
Programming languages
- Ladder logic
- Structured text
- Function block diagram
- Sequential function chart
- Instruction list
Other controller families
- Schneider Modicon
- Mitsubishi
- Omron
- Beckhoff TwinCAT
- CODESYS
- Automation Direct
- Delta
Fieldbus and networks
- EtherNet/IP
- Profinet
- Profibus DP
- Modbus TCP
- Modbus RTU
- DeviceNet
- AS-Interface
Product names here are the tools the work is done in. Experience with a platform is a fact about an engineer’s history; it is not a partnership with, or an endorsement by, Rockwell Automation, Siemens or any other vendor.
Hiring it, and doing it
The same page serves two readers. One is deciding who to trust with a running machine; the other is deciding whether the job is worth a proposal.
What to look for in a PLC programmer
The risk in this work is rarely whether someone can make the machine run once. It is whether the program is still maintainable after they have gone.
- Experience on your controller family, named — Studio 5000 and TIA Portal are two different jobs
- A program you could hand to a plant electrician: commented routines, consistent tags, no bare numbers
- A considered view on alarms — which faults latch, which self-clear, and what the operator is told
- Willingness to be judged on a factory acceptance test rather than on a demo video
- A clear answer on whether commissioning, travel and site time are inside the price
- Ask to see a sample routine. In this trade the code is the portfolio.
If PLC work is what you do
A client reads your profile before they message you, and Ingenium requires it to be complete before you can send a proposal or accept an offer.
- Put the platforms and versions in your skills, not just “PLC programming” — that is how the jobs are described too
- List the drive families, instruments and fieldbuses you have actually commissioned, not only read about
- Use job history to show the industries: packaging, water, food, automotive, oil and gas
- State whether you travel, and the notice you need for site work
- Skills, resume, job history, education, hourly rate and work schedule are all required before you can apply
- A client opens the conversation — by inviting you to a job, messaging you, or sending an offer
How you hire a PLC programmer here
Ingenium is a marketplace, not an engineering firm. It does not do the work — it is where the job is described, proposals are compared, and the contract and the money are held once terms are agreed.
Post the job
Describe the scope, the equipment involved and the site, and post it under Controls Engineering. Posting is free. You can also invite a specific engineer to the job, or message one from their profile.
Read the proposals
Engineers who do this work reply with their rate and how they would approach it. Messaging is open from the moment a client starts the conversation, so the scope can be argued out before anyone commits.
Send an offer
An offer sets the payment model and the terms. Fixed price is split into milestones; hourly is invoiced weekly from logged time. The model is chosen when the job is posted and cannot be swapped later. A saved card is needed before an offer can go out.
Run the contract
An accepted offer becomes a contract with a shared work diary, tasks, time entries, comments, invoices and expense claims. Funds are held by Stripe and released when the client accepts the work.
Which payment model fits
Fixed-price milestones suit a defined deliverable — one machine, one program, a known I/O count — and stop both sides arguing about hours. Hourly suits a retrofit, where the first task is reading an undocumented program before anything can honestly be estimated, and it suits commissioning, where the schedule belongs to the plant rather than to the engineer. Plenty of PLC projects want both: the program fixed-price, the site time hourly. The model is set when the job is posted and cannot be switched afterwards, so that means posting two jobs.
The full flow from posting a job to getting paid covers both models and where the money sits in between. Everything a contract carries — time tracking, milestones, messaging, invoices, payouts — is listed on the features page. Or create an account and post the job.
Usually part of the same project
These jobs tend to arrive together. One engineer sometimes covers two of them; sometimes it is two contracts.
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