What is a PLC?
A Programmable Logic Controller (PLC) is a ruggedized industrial logic controller that can control a specific process, machine function, or even an entire production line for industries, including but not limited to: petroleum, steel, automotive, aerospace, printing, food, textile, medical, corrugating, plastics, etc. PLCs are flexible and adaptable to almost any application.
A PLC functions by receiving information from sensors or input devices, processing the data received, and generating outputs based on guidelines pre-programmed into the device. Every PLC is composed of three main parts: Input, CPU, and Output. Depending on the inputs and outputs, a PLC can:
- Start and stop processes automatically
- Use Inputs and Outputs for the PLC controlling one machine to interface with other machines.
- Precisely time operations and accurately count actions of the machine or items being processed.
- Control a variable device (e.g. heater or pump) based on information measured from the Input side of the PLC.
- Perform complex math
- Receive input information from remote or distant locations and send output commands to remote or distant locations.
- Generate alarms if a machine malfunctions
- Accurately monitor high speed operations, lengths and speeds with special functionality within the PLC.
- Communicate with devices (e.g. weighing scales, bar code readers, etc.) to perform tasks such as monitoring and recording run-time data to measure machine productivity or operating temperature
A PLC program is usually developed on a computer using controller specific programming software, and then the PLC program is downloaded to the PLC. Most PLC software is programmed in Ladder Logic. Ladder Logic is the traditional programming language. It mimics circuit diagrams with “rungs” of logic read left to right. Each rung represents a specific action controlled by the PLC, starting with an input or series of inputs (contacts) that result in an output (coil). Because of its visual nature, Ladder Logic can be easier to implement than many other programming languages.
What is a Smart Relay?
Programmable Logic Relays (aka Smart Relays) - essentially PLCs in a simpler form – function by replacing physical relay logic with logic that can be programmed into the device. Programmable logic relays are used in industrial situations where the input/output points are in small quantities. Logic relay technology can be modified quickly and easily since the internal programming replaces the function of physical parts such as relays and timers. Based on feedback from sensors or other industrial equipment, the smart relay’s timing program can be modified to start, stop, slow, speed-up, delay, or advance industrial processes according to data received from individual mechanisms and material characteristics. In some cases, it may not be necessary to physically alter the control panel itself, even if additional sensors or other signals are added to the process.
Due to its number of inputs and outputs, a single PLR can take the place of various control devices and circuits by consolidating and streamlining controls from multiple pieces of equipment. A smart relay can perform a variety of functions such as counting, sequencing, timing, and real-time clock operations. These devices can automate a specific process or machine function in applications pertaining, but not limited to:
- Industrial/ commercial/ residential automation (i.e. irrigation, heating/air, alarm systems, automatic door opening)
- Industrial machinery (i.e. compressor/motor/pump control, bending/welding machines)
- Industrial refrigeration (i.e. timers, temperature control, humidity/ventilation control)
- Conveyor systems (i.e. stop/ go controls, automatic stopping)
- Industrial Level/pressure control (i.e. valve opening/closing, pump change, silo filing/draining)
The smart relays offered by FactoryMation can be programmed in Ladder Logic or Function Block. Ladder Logic is the traditional programming language. It mimics circuit diagrams with “rungs” of logic read left to right. Each rung represents a specific action controlled by the logic relay. Function Block is a programming language that is used to describe functions between input and output variables in programmable controllers. This programming language uses signal and data flowing through blocks (i.e. software elements) to then program instructions which yield output values.