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Electrical Switching Using A Programmable Logic Controller
by Eugene Kowch, P.I.D. Consultants Inc.

The Programmable Logic Controller is the solution to today's electrical switching requirements. The PLC is as reliable as a traditional switch, but has the ability to solve the complex switching requirements of today.


Switch - noun - A device used to break or open an electrical circuit or to divert current from one conductor to another.

The electrical switch used today is a very reliable and affordable means of switching electrical systems, like lights, off and on. These electrical switches have been around since the invention of electricity many years ago and not much has changed in their design. These on/off switches have become a standard in many an electrical design, because of their simplicity and ease of operation.

Recently these same switches, because of their simplicity, are making it difficult for electrical designers to solve some complex switching requirements. Wall clutter, switching from multiple locations, flexibility to assign switches to other loads without major renovations, tie-in with security and other electrical systems and control from personnel computers to name a few. Electrical switching using a Programmable Logic Controller (PLC) will help solve all these and future switching requirements.

Programmable Logic Controllers are not a new product in the market place. These controllers have been in use for over 50 years in the industrial world. They have proven to be a very reliable and affordable means of switching complex electrical systems in many manufacturing and large plant applications. These same PLCs can now be used in commercial and residential electrical designs to solve the complex switching requirements mentioned above.

Low voltage keypads, strategically placed throughout the office or home, provide the inputs for the PLCs to determine which outputs to activate. These keypads have multiple buttons in a single gang configuration, which removes the wall clutter that conventional switches create.

Each button on the low voltage keypad is a unique input to the PLC. The input is assigned to an output only through a logic program resident in the PLC. Therefore any button on any low voltage keypad can turn on or off any or all-electrical systems, like lights, throughout the facility. The electrical designer now has the ability to switch loads from multiple locations and the flexibility to assign switches to other loads.

Security has become an important issue in the commercial and residential community. Electrical designers ensure that a security panel is installed in all facilities but do not have a means to tie-in to other electrical systems, like lights, to enhance the security system. With a PLC, the security panel can switch one of the low voltage inputs and have all or some of the lights flash off and on when an alarm situation occurs.

Local Area Networks (LAN) are becoming common place in all commercial and residential installations. Computers throughout an office or home are being networked together and also connected to the outside world via the Internet. Electrical designers, using the PLC, have the ability to connect PCs to all the electrical systems in the facility for remote control or reprogramming.

The Programmable Logic Controller is the solution to today's electrical switching requirements. The PLC is as reliable as a traditional switch, but has the ability to solve the complex switching requirements of today.