My PLC (Programmable Logic Controller) Experience

At work there are still a lot of things to be done. The latest, hottest and interesting job in my list is the PLC (programmable logic controller) upgrading in my plant and control room. For me, this is a very enriching project and an excellent learning experience for me. All these while, I've been monitoring the temperature, flow rate, pressure, utilities, processes, costing, equipments, instrumentations, reports etc., but now I'm going to get myself a little bit familiar with the plant control system. Previously, at university, I don't really fancy process control; and advance control subjects, but now, I'm beginning to be develop some interest in them. However, if I'm not mistaken, the subjects don't really touched a lot of PLC stuffs.

OK, back to the present moment. Every process plant must have their own PLC to run the process or production plant. If not, the plant operators have to switch the pump, flow meter or other instruments manually and that's impossible at this era. It will be very difficult for them to control and monitor a running plant.

Lets see some definitions of PLC. According to Wikipedia: "A PLC is a digital computer used for automation of industrial processes, such as control of machinery on factory assembly lines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result."

A non-technical term to describe a PLC: A PLC is the type of computer that controls machines. The PLC is used to control and troubleshoot machine. The PLC is the brain of the machine. Without it, the machine is dead.

For the past few days, I've been studying the input/output (I/O) arrangements at the control panel. These connect the PLC to sensors and actuators. PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of complex positioning systems. On the actuator side, PLCs operate electric motors, pneumatic or hydraulic cylinders, magnetic relays or solenoids, or analog outputs. The input/output arrangements have external I/O modules attached to a computer network that plugs into the PLC. The I/O points consists of digital input, digital output, analog input and analog output. I checked them and counted how many spare I/O points are available to be used for additional pressure transmitter, RTD, inverter and pump that we're going to install (which is part of some slice of plant upgrading projects).

Hmmm....I guessed, that's enough for some brief introduction on the PLC. I may continue about my PLC adventure in future.