I would like to know what training I will have to undergo before I could undertake training in Automation like PLC, SCADA or HMI? Which would be preferred Electrical or Electronics Engineering?
In my opinion,
whatever your major you took, whether its a electronics, electrical, computer or physics, prior to take basic automation system training, you should have, at least well completed course on digital electronics and be fluent on one of programming language such as C or basic, since programming of PLC based control system will be based on both topics and they are will be your basis to learn more advance automation system.
I believe, your major only differentiate your preferred methods of programming. As example electrical guy more prefer to use ladder, while guy with electronics background will prefer to use Function block, computer or IT background will be more fluent on structured text programming methods.
Also, application wise, different major will differentiate programmer or engineer understanding to the application, as example, PLC programmer with electrical background will be more easy to understand and implement PLC to power generation and distribution application, PLC programmer with mechanical background or power electronics background will be more easy to understand and implement PLC to mechatronics application, one with physics background will be more easy to implement PLC to the process control application, etc.