Can’t get an Interview without PLC Training ?
Back in the day, when automation systems were quite primitive, the call to a machinery breakdown sent you off to get the electrical drawings, these were typically two or three really large sheets of paper folded like a map, always covered in oil, the important bits missing and circuit modifications drawn on with a pencil, (you later find out that the modifications don’t relate to your machine anyway !)
You would arrive at the machine, open the panel doors, it’s like a tropical rainforest in there and there are eight rows of din-rails full of relays and contactors , there’s a few timers, a batch counter and a dc drive. The power supply smells like an unwashed sock, there is no lid on any of the trunking and there is a terminal block which runs the full height of the panel. The whole panel and floor vibrates every time the compressor starts up about 50metres away.
The Operator makes the machine go through a cycle so you can observe the symptoms of the fault and the two hundred relays begin to pull-in and drop-out but it’s so fast and hypnotic that it’s impossible to follow the sequence as they perform their prewired logic but suddenly they stop and you’re jolted awake because it’s not yet the end of the cycle, the cycle has terminated early. Someone comes over to you and asks how long you’re going to be ? … a few answers spring to mind but you can’t help thinking that today might be Day One, Week One for this fault.
You might also be thinking that the cause of the fault could be a break in one of the thousands of field wire terminations feeding the terminal blocks in the panel or maybe it’s one of the wires connecting the relays, timers and counters together to create the logic circuit which automates the machine and that the vibration from the compressor is work-hardening all the copper wiring and breaking it, another thing, the PSU still smells like a sock ?
Today, the PLC lies at the heart of many automation systems. The PLC does away with all of those electro-mechanical Din-rail relays with their hard-wired copper connections and massive control panel.. Instead, the PLC utilises internal logic relays which are located within the memory of the PLC so they have no copper connections to fail and typically the PLC has thousands of them for you to select and use in a surprisingly familiar on-screen ladder diagram. Consider already, the major improvements in reliability the PLC is offering.
So, all of these PLC logic relays (memory relays) are used to automate the machine by “programming” the relays in series, parallel and latching combinations. PLCs also employ programmable timers and counters as you might expect plus a range of special devices such as comparators and shift registers, data storage and data Move instructions and yes ! all of these can be programmed within your ladder diagram and are very easy to monitor in real time for fault finding on your machinery.
So, most people will need to learn about PLCs so they can quickly plug a PLC programmer (laptop) into their machines’ PLC and monitor logic operations in real time, used in this way it’s an exceptional fault finding aid to help you resolve faults on the machine. Other people though will learn about PLCs so they can make program modifications and operational updates to their own plant and machinery.
The big secret is, that learning how to do this can be reliably achieved in a very short time especially if you have an electrical background,…. by attending a PLC training course.
For an intermediate level course, you might consider 4 or 5 days training. Select which PLC you’d like to do the training with, some examples would be Siemens, Mitsubishi, Allen Bradley. Contact your training provider and ask for their Learning Outcomes for the PLC course. A typical intermediate level course might include the following:-
- Evaluate the choices between Hard-wired and PLC controlled systems
- Identify hardware features of the PLC
- Identify the software features of the PLC
- Determine the addressing system of the PLC
- Recognise number systems used by some PLCs, bits, bytes, word, DW
- Safety considerations
- Use the PLC software to write a basic PLC program
- Document the program
- Connect the programmer to the PLC and go online
- Send the program to the PLC
- Monitor the program in real time
- Use simulator switches to test the program
- Create programs for basic logic operations, AND, OR etc
- Create simple programs using latch, set/reset, memory relays
- Create simple programs using timer, counter, comparator, move
- Create simple programs using Shift Register, Data Operations, Master Control
- Practice using FORCE operations.
- Wire up the PLC to a training rig of some description and write a program to control the rig as required.
- Take part in a PLC fault finding exercise
PLC control systems are so commonly employed today that some Maintenance Managers, HR people and Recruiters are beginning to consider PLC skills are a necessity in the Skills Profile of the Maintenance Engineer, particularly in a manufacturing plant which is loaded with automation. Fortunately there are quite a few training providers in the UK offering excellent PLC training.