PROGRAMMABLE CONTROLLERS HAND BOOK – L.A.BRYAN
Programmable logic controllers, also called programmable controllers or
PLCs, are solid-state members of the computer family, using integrated
circuits instead of electromechanical devices to implement control functions.
They are capable of storing instructions, such as sequencing, timing,
counting, arithmetic, data manipulation, and communication, to control
industrial machines and processes. Figure 1-1 illustrates a conceptual
diagram of a PLC application
Programmable controllers have many definitions. However, PLCs can be
thought of in simple terms as industrial computers with specially designed
architecture in both their central units (the PLC itself) and their interfacing
circuitry to field devices (input/output connections to the real world).
As you will see throughout this book, programmable logic controllers are
mature industrial controllers with their design roots based on the principles of
simplicity and practical application.
