Programmable logic controllers (PLCs) and programmable automation controllers (PACs) are industrial computers constructed and adapted for manufacturing environments. These computers are the brains of a manufacturing operation, providing highly reliable control of automation equipment.
PLCs and PACs are very similar to each other as they both perform the same essential functions. And, with modern technology, their differences are becoming more blurred. All automated systems are built with a PLC or PAC to control individual machines or stations. Additionally, the computers can be programmed to control a group of machines or stations.
The most notable difference between PLCs and PACs is their programming interface. PACs are more intricate, using C or C++. PLCs, on the other hand, are programmed using ladder logic, a programming language that employs symbols representing an electrical schematic of relays. These programming differences create distinctions in the architecture and capability between the two computers.
PLCs have simple program execution scans, but with limited memory and discrete input/output (I/O). Modern PLCs are capable of high-speed I/O, sequencing, and proportional-integral-derivative (PID) control in addition to digital and analog I/O.