History of PLC : Before and After PLC Exist

History of PLC - As we see, so many industries that rely their system on PLC. For a deeper understanding, There are two conditions based on the existence of PLC, before and after the PLC exist. But first, let see what is PLC?

What is PLC?

PLC is the acronym of Programmable Logic Controller. Basically, PLC is same as a computer, a digital computer. This device builds specialized to fulfill the industrial requirement as a system controller. PLC can be used in the assembly lines, robot control system, manufacturing control system and others. PLC was introduced by the automobile industry to replace relays and timers. 

Example of PLC (wikipedia.org)

Before PLC Exist

      So as we already know before, PLC built to replace common relays and timers. Most of the industries rely on relays and timers for their system control before the PLC exist. Relay work by giving electricity to the coil inside of it. When the coil has enough electricity, it will produce a magnetic field that pulls the metal so some of the contacts will be disconnected and others will be connected.

      When the electricity is cut from the relay, the coil will de-energized and the magnetic field is gone. Because of it, the metal will no longer pull and back to its original position. Well, a timer has the same logic, when the required time is fulfilled, the contact will be connected, when the electricity is cut, the timer needs to recounting again.

What's the problem with the relay?

     If you only need to wire only a few relays, that's not a problem. Try to imagine if you need to wire so many relays and it starts to crowd, it won't be easy to do trouble shooting. The other problem is regarding its speed, when you need a repetition or in other thing energizing - de energizing the relay with fast, the relay will late to respond or it will become error. If that thing happens, it will put your system in error. 

Relay panel (wikipedia.org)

      The faster and more movement of the metal contact, the more chance that the relay will wear out. The other problem is the space, more relays mean more space, more cables, and more cost. Based on that, it required a new technology or device to replace relays, a device that more complex but small in size and that is PLC.

Who found the PLC?

     PLC was found by Richard E. Morley an employee of Bedford Associates (Bedford, MA) in 1968, its first use was in the automotive industry. At the first, the name of this device is Modular Digital Controller (MODICON). Then it changes to Programmable Logic Controller (PLC). After the words spread, PLC becomes more popular. MODICON PLC was the first supplier of the PLC. 

    In the first time to program the PLC, special devices were used. This device contains NO contact, NC contact, and any other contact or logic. Nowadays we use computer/laptop to program the PLC. 

After the PLC Exist

       So what's happening when the PLC exist?. When the PLC start exists and becomes more popular, more industries are changing their system control that using relays and timer, with the PLC. It has been proved that PLC is a device that reliable and easier to use. By using PLC, the system response time has significantly improved, that also provide some new possibility in the automation process.

See : When and Why using PLC? 

       Not just that, PLC changes the need for timers, relays, counters. That means less cost are needed to build a system control. As the PLC getting more improvement, there is growth in the number of input/output, timer, counter, relay, input/output analog, also some additional logic like arithmetic and others.

PLC in panel (wikipedia.org)

     Because PLC is more involved in the manufacturing process, sometimes it demands to combine few PLC into one system control. This can be done by using serial communication or other forms of communication. It depends on the manufacturer, some of this communication device is exclusive.

Example of PLC program (private doc)

      Nowadays, more plc manufacturer is involved, each of it provides a different specification. Different manufacturer and type mean different instruction, but the basic still remain the same. So if you know the basic, you just need to know the instruction name for it.

Feel free to share, like, or comment this article. Thanks for reading.