PLC: Hard vs Soft

Hello again.

Yes I am continuing with the theme of Programmable Logic Controller, that much overlooked but so critical feature. This time around I am going to explore the age old question of whether a software or hardware based PLC controller is better. (Spoiler alert it is hardware).

Many people would argue that a software based solution is easier. Most MBE systems already have a basic software package that communicates with most of the system hardware in order to run recipes and grow samples. It is therefore fairly intuitive to add some kind of a “Watchdog” feature to that software. Intuitive and fairly easy.

Easy does not equate to better. Imagine if Michelangelo had told Pope Julius II that despite his idea to pain the ceiling of the Sistine Chapel, it would be must easier in fact to paint the floor, and in crayon. (Note I recently visited the Rome and it was amazing, hence the reference).

My point is that easy does not equate to better. A software watchdog is better than no watchdog at all, but bear in mind that Windows is inherently equally flexible and unstable. The all seeing watchtower monitoring for constant threats should not reside in the land of BSOD (that is Blue Screen of Death) and OIASWYITMOSINTR (that is Oops I am sorry were you in the middle of something I needed to restart).

The fact is PLCs are hardware based for a reason: A dedicated microprocessor with a single task monitoring and dealing with faults. Some of the more complex PLCs are very rugged computers, but for MBE with a few dozen inputs and outputs, a single microprocessor is plenty.

That is not to say a PLC cannot have a sleek, elegant user interface. I have to admit I do love a sweet UI. A PC based UI that can add, edit and delete “rules” for the PLC can only be a good thing. The actual critical task of monitoring and reacting should however be performed on a dedicated little blinking box that does not get distracted by services and kernel threads and spyware and viruses and… and… and…

Thanks for reading. See you all tomorrow.

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One thought on “PLC: Hard vs Soft

  1. Pingback: PLC: Central vs Distributed | Dr. Faebian Bastiman

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