A question we are quite frequently asked: why use a PC as controller, rather than a true industrial "classic" PLC ?
It is obvious that the usefulness of traditional PLCs can not be challenged in many cases. The micro-PLCs, for example, are very simple and convenient, for a limited cost that the PC can not compete. While offering PC-based products, Optimalog makes no religion of the use of the PC as PLC, and indeed some of the applications that we realized are done on conventional PLCs, which we know very well.
However, the approach consisting to systematically exclude the PC from the PLC function does not seem more reasonable. The PC in workshop is today a reality in many companies, not only to make supervision. The production machine entirely driven by PC is not at all an isolated case: many of our customers today have opted for this solution and are satisfied.
Indeed, for whom take a closer look, the PC has for him many advantages.
First, the word "PC" actually covers a wide range of equipment. From "standard" PC assembled by the vendor next door, passing through the office station, up to the powerful application server, the PC has often the image of a house or office only machine. But we must not forget the industrial PC. They have nothing to envy today to the classics PLCs in terms of reliability and robustness. Compatibles to each other, these different types of PC offer incredible choice, to adapt perfectly to the environment and the application which is intended. Moreover, the multiplicity of supply makes the market very dynamic, with rapid technical developments and cost much less, at equal power, as in the case of conventional PLCs.
On the other hand, the use of PC allows an opening that do not offer the conventional PLCs. It would not come to the idea to connect automation equipment from Schneider on Siemens equipment : users of classic PLCs are indeed completely captive of manufacturer they have chosen, and pay a high price. In the PC world, on the contrary, software and hardware with different providers live together within a single application. It is possible to insert in the PC an impressive variety of electronic boards concerning all industrial and scientific fields. In the vast majority of cases this is done without any problem. The capabilities of the PC communication standards also allow it to integrate virtually all types of devices (Ethernet, USB, Firewire, serial connection, etc…).
Example industrial PC (Advantech)
Alongside this diversity and openness, the PLC appears very poor. To that, PLCs providers respond "no problem of compatibility between equipment from the same supplier", "placing into service simplified", "training provided by the manufacturer", etc.. Arguments often just, but not always. Experience shows us that things are not perfect, alas, in the case of classical PLCs, or in the case of the PC. But the assurance of having one manufacturer responsible for the operation of the whole is very reassuring for the buyer because it is often an important investment. Solutions are therefore often bought two, three, five times more expensive price for a certain peace of mind. Will manufacturers succeed so long to convince users that they ultimately save money by buying much more expensive their products?
Another argument for manufacturers PLCs : the level of training required for the implementation of an application. The formation of a control technician is more focused and less long than a computer engineer. But the validity of that argument fades over the years. The automation would be quite difficult today to work without using a PC, which runs almost all programming workshops. Whether their application also works on the same PC does not, therefore, very much. On the other hand, the technical arguments concerning the programming or facilities such as changing online do more, different products on PC for automation, as Optima PLC, providing exactly the same opportunities and tools that the PLCs, often better and less expensive. In Optima PLC, the application can be scheduled to SFC, contact scheme (ladder) and with other languages 61131-3 IEC compliant, and not in C++ or Basic.
Graphical Programming for automation (Optima PLC)
Finally, the argument of reliability is the ultimate weapon of conventional PLCs manufacturers. But this argument has been short-lived. First, as we said earlier, if the hardwares called "PC" are very diverse, it is perfectly possible to use PCs today whose reliability has nothing to envy the classical PLCs, while remaining below the prices of them. On the other hand, if the vulnerability of PC software has often been emphasised in previous years, it is clear that operating systems available today are far more stable and secure. It is clear however that the opening of PC software will pay a higher vulnerability, compared to that of the PLC with which the user is very strictly supervised. But experience shows that applications on a PC made in the rules are neither more nor less reliable than those on conventional PLC. And by the way, these same PLC manufacturers add more and more frequently in their catalogue PCs which have often not much different compared to those available elsewhere, apart from ... their prices.
Based on these findings, more and more companies look to objectively on the PC-based solutions for their automation problems. The decisions are then not taken in positions of principle anymore, but actually weighing the advantages and disadvantages of each option, and the benefits they can derive from them. Optimalog wishes to register in this pragmatic approach : taking advantage of this excellent tool that the PC can be where warranted, and only in this case.
With a product like Optima PLC, Optimalog proposes a solution that supports software compatibility of the equipment used on a PC. And for quite reassure our customers, we also propose PC-based solutions fully assembled according to the needs of their application, configured, tested, ready to be programmed and put into service.
