Technology today is advancing by leaps and bounds, driven both by the demand for higher product quality and by competition between brands.
Every sector needs technological growth and continuous improvement and optimisation of all its processes and products.
For technology, and society with it, to move forward, large industries must research and invest in their plants in order to offer products with cutting-edge technology and higher quality.
Meeting all these requirements calls for every process to be controlled and automated, achieving higher output and better quality.
What do we mean by automated processes?
To answer this question, we first need to define industrial automation: industrial automation is any automatic intervention that helps industry improve and optimise a process.
Thanks to today's technology, such as PLCs, SCADA and communications, automating any industrial process is easier than ever.
What are the benefits of automation?
• Less manual labour in processes. Automating machines or processes reduces manual work and optimises tasks.
• Higher output. Any automated process increases production thanks to simpler operator tasks and the improvements applied.
• Less maintenance. A well-automated process with proper preventive monitoring reduces technical problems and helps improve production and quality.
• Guaranteed quality. The quality of any automatic process improves because human error is minimised. For example, in the inspection of a part whose dimensional tolerances must be checked on a very small scale, a properly adjusted machine will always work the same way, unlike an operator.
All, or practically all, automation must be controlled by one or more PLCs.
What is a PLC?
It is a programmable electronic controller. The name stands for Programmable Logic Controller.
It can control anything from a simple machine to real-time sequential processes, such as any large-scale industrial process.
The PLC must be programmed with software containing the conditions required by each application so that it works correctly.
Controllers work through input and output terminals, which can be digital or analogue.
What does this mean?
It means that a PLC can read any kind of electrical sensor through its inputs, such as a push button or a switch.
It can also read all kinds of physical values through analogue sensors, such as pressure, temperature or level sensors.
Because it has outputs, it can also act on different elements: cylinders, motors, relays or contactors, and it can even use analogue outputs to regulate valves or, in lighting, some types of luminaires.
There are different models and sizes, always depending on the application to be automated.
Some of the best-known companies in the automation world are:
Siemens, Rockwell (Allen-Bradley), Schneider Electric (Telemecanique) and Omron, among others.
Each of them offers different PLC models for all kinds of applications, always adapted to the need.
The parts of a PLC:
Inputs: PLC inputs can be digital or analogue.
• Digital:
Digital inputs are usually powered at 24 V DC. They are contacts that, when energised, activate an internal signal in the PLC that the software can use as a condition. Any button, physical switch or proximity sensor can activate a digital input.
• Analogue:
Analogue inputs read physical values: temperature, pressure, level, potentiometers... There are two ways of reading them: current loop (4-20 mA) or voltage (0-10 V). The program scales the electrical reading within a range to obtain the actual physical value.
For example: a 0 to 200 °C temperature probe connected to a current input. The minimum input value will be 4 mA, which corresponds to 0 °C.
If the reading reaches 200 °C, on the other hand, the input value will be 20 mA.
Outputs: PLC outputs can be digital or analogue.
• Digital: there are two types.
- Relay: low-power mechanical contacts to drive low-consumption actuators. Their switching cycle is much slower than that of transistor outputs.
- Transistor: very fast digital contacts. They cannot be used to switch power directly; interface relays are required. PLCs with this type of output are more expensive. They can be used, for example, as pulse outputs for frequency drives or for solid-state relays driving heaters.
• Analogue:
Analogue outputs are similar to analogue inputs but work the other way round. A signal is sent to the actuator through a current loop (4-20 mA) or a voltage (0-10 V). For example, an analogue output can provide the speed setpoint of a frequency drive. In this way any physical variable can be regulated from the PLC itself.
Automation has evolved so much today that it goes hand in hand with connectivity, which is why the PLC is not the only important element. A PLC can be controlled through different software running on screens or computers.
The programs used to control and visualise all the automatic processes performed by the PLC are called HMI or SCADA software.
HMI (human-machine interface) software runs on a screen, for example a touch screen. Its purpose is to control the whole PLC from a screen next to the automated process, providing visual and touch control of the entire process.
This type of software gives quick access to the parameters of the process or machine and simplifies the operator's work.
Unlike HMIs, SCADA systems are more complex software packages usually installed on a computer. They are similar to HMIs but more powerful: more complex screens make it possible to control and visualise not just a single process or machine, but entire industrial plants with several processes.
SCADA systems are usually deployed at different control points in industrial plants, since they can be operated and displayed from several computers. This provides full control of all the PLCs in a plant or, over the internet, of plants in other locations.
Both types of software offer functions such as actuator control and sensor detection, trends and historical data, data export and import, alarm and process error handling, user management and many more.
There are many SCADA platforms, such as Siemens WinCC, Vijeo Citect, Rockwell Automation FactoryTalk View (RSView), AVEVA InTouch (Wonderware) and Ignition, among others.
HMI screens and SCADA systems can communicate in different ways, for example:
Ethernet, AS-i, PROFIBUS, PROFINET, Modbus, Fieldbus...
Each has its own advantages.
Today, PLCs tend to communicate with their screens over Ethernet (TCP/IP), as it offers high transfer speeds and a large bandwidth. It also allows any device to be connected over the internet for full control from anywhere.
Some of the existing types of communication are explained below:
• AS-i (Actuator Sensor Interface):
At field level it is the simplest to control and very fast (5 ms cycles). Up to 31 slaves (62 with A/B extended addressing) can be connected to the master-slave bus.
It transmits 4-bit packets and can be used over segments of up to 100 m, extendable with repeaters.
• PROFIBUS:
The most widely used standardised industrial communication system and a European reference standard for fieldbuses. It supports up to 127 nodes and works on a token-passing basis. It uses a twisted pair (up to 1,200 m per segment depending on the speed, extendable with repeaters) and can transmit up to 246 bytes in 90 ms cycles.
It is used in distributed I/O to connect instrumentation or different devices to each other.
• PROFINET:
An industrial Ethernet standard. By combining PROFIBUS technology with conventional Ethernet, communication has been significantly improved.
All PLC systems, instrumentation and I/O are now adopting this system.
In addition to the features of PROFIBUS, it offers:
A virtually unlimited number of nodes, greater scalability, full TCP/IP compatibility and real-time web or internet connection. Standardised connections thanks to conventional Ethernet cabling, and wireless communication with security protocols that avoids extensive wiring.
• EtherCAT:
An open standard (IEC 61158) based on Ethernet protocols. It is currently one of the fastest industrial communication systems. The name stands for Ethernet for Control Automation Technology.
It can send and receive data packets on the fly: there is no need to request data in order to receive it.
It is designed for industrial environments, and its communication speed is measured in μs (microseconds).
It is used in complex industrial processes that need to process large amounts of data in very short times.
• Modbus:
An industry-standard master-slave system (client-server in Modbus TCP) that can run over RS-232, RS-485 or Ethernet.
The master sends requests that the slave must answer. It is used in instrumentation to read sensors, drives, PLCs... The master can also send requests to control simple parameters of any device connected via Modbus. Up to 247 slaves can be connected to one master, and data is transmitted in ASCII or RTU format.
Finally, it is worth stressing that automation will be ever more closely linked to industry. It is gradually being built into every new process, and obsolete processes are being upgraded to continuously improve every product.
Industry 4.0 and IIoT: the next step
Automation is no longer limited to controlling machines and processes: today it is also about making use of the data they generate. This is known as Industry 4.0 or IIoT (Industrial Internet of Things): connecting PLCs, sensors and SCADA systems to obtain reliable real-time information.
With well-collected and well-organised plant data it is possible to:
- Calculate indicators such as line efficiency (OEE), downtime or consumption per product.
- Move from corrective to preventive or predictive maintenance, detecting deviations before they cause a breakdown.
- Ensure the traceability of every batch: which recipe was used, which process values were recorded and who intervened.
- Reduce energy consumption by adjusting the operation of pumps, motors and heating equipment.
How should you start an automation project?
There is no need to tackle everything at once. We recommend starting with an analysis of the existing installation and the customer's objectives, defining a first, well-scoped phase with measurable results, and growing from there. An open architecture, well planned from the outset, avoids having to redo work later.
If you are considering automating a process or modernising an installation, contact us and we will study your case with no obligation.