FAQ

PLC stands for Programmable Logic Controller. It is a controller that acts like the "brain" of a machine: it makes high-level decisions and controls the functions of a production machine. In industry, PLCs handle tasks such as motion control and process monitoring. A single PLC can serve as the central controller for an entire system, under which there may be several other PLCs. PLC controllers can be used in virtually any industrial automation task.

Both nothing and everything! The basic idea is the same: programming the logic that controls machines and processes. The differences are more superficial — typically manufacturers provide their own programming tools, whose user interfaces and the syntax of their programming languages (i.e. how commands must be written so the machine understands them) tend to differ. 

Once you understand fundamental logic, switching manufacturer is usually just a matter of learning a new tool.

Technically usually yes, but in practice it's seldom worthwhile. The problem is that old programs rarely fit neatly into the requirements of the renewed project. For example, in an old production line you might not want to replace the entire machine, but its program might have reached end-of-life. If the program is transferred as-is, you also carry over all the modifications, fixes, or deprecations that have accumulated during the machine's lifecycle — often including unnecessary code.And if during the project there is a need to add modern requirements, the old code usually does not adapt very cleanly — which increases the cost.

Starting from a clean slate and building a new solution according to modern standards is often the most cost-effective option in the long run. 

It’s better for everyone to not try reusing the old program, but instead clarify exactly what functionalities are needed and build a new solution. A video or documentation of the machine running gives a far clearer picture of what we need to achieve than relying on outdated code.

This depends entirely on the case. The more precisely the goals and needs are identified and defined at the beginning, the more realistic the schedule you can get.

Along the way, there are often realizations and additions. The best starting point is a good preliminary assessment — but leave flexibility in the plan for possible changes.

This is quite a big topic, typically belonging more to mechanical design than pure programming. For example, there might be risks of crushing, and safety definitions are governed by machinery directives. Modern machines often include redundant safety circuits and safety logic that operate separately from the main production program. Safety interlocks such as door safety switches and emergency stop circuits are connected to these safety circuits. When a door is opened or a safety device is triggered, the machine is brought to a safe state — for example by releasing pressure or cutting off control voltage and compressed air.

Error handling means that the program detects abnormal situations and reacts in a defined way (e.g. alarms and/or halting processes). With good design and structured approach, the program can also recover from exceptional situations correctly — regardless of what the user does or in what order. A well-designed program should not even allow improper user actions.

In PLC programming, several specialized languages are used; most are based on the IEC 61131-3 standard. We most commonly use the following three.

Ladder Diagram (LD)

Also known as "ladder logic." This graphical language was developed so that, e.g., electricians and automation engineers could easily understand its structure, since it resembles electrical circuit diagrams. It is especially suitable for relay logic and control implementations. For example, LD is common with Omron.

Function Block Diagram (FBD)

Another graphical language, where the program is built from functional blocks. It is well suited for process control and PID regulation (e.g. controlling a furnace temperature to stay at a desired value). FBD is used, for instance, by Siemens

Structured Text (ST)

A textual, conventional programming-language–like syntax. ST is quite similar across manufacturers, so when we write ST inside so-called function blocks, we can often copy that code almost directly to another manufacturer’s environment. That saves a lot of time and therefore costs.

In many ways! The IT-side and industrial automation side increasingly overlap. Common methods include industrial fieldbuses such as EtherCAT and PROFINET, as well as older systems such as Profibus. Additionally, connections can be hard-wired — via direct inputs/outputs or voltage-based signal lines.

Nowadays it's also common to use Ethernet-based industrial protocols (e.g. OPC UA) or general IP-based solutions between devices. Where in the past separate middleware or PC connections were often required, modern PLCs can read and write data directly — for example into databases.

The same answer applies as with differences between manufacturers: both nothing and everything! What is distinctive is using languages like Ladder, which you rarely see elsewhere. Though like other programming languages, PLC languages vary in syntax and representation, if you know how to think in terms of good design — how to build machine control in an efficient, systematic way — then you can apply those skills in almost any programming environment.

We’re often asked this! The small differences between manufacturers can be learned quickly when you have a good foundational understanding of how machines and automation work. What matters most is the ability to build logic and structure processes correctly — not whether you’ve worked with a specific brand before.