We have had a look at the basic techniques to use when having to fault find a circuit. The next topic that should be added to this is the need for us to have a good understanding of PLC’s
With the way things have changed, you will come across a PLC in just about every control panel lately. So what does that mean for us as Electricians? To put it quite bluntly, you need to ensure you understand how they work, how to connect to them and use the monitor function and also understand basic ladder programming.
Why is this important? Is that not the “programmers” domain? When these devices got introduced, that was how it used to be. The Electrician did not need to do or understand the programming side of it but that has changed rapidly. If you have been tracing a fault from the field devices and you have all systems ready up to the PLC but the machine will still not start, can you afford to wait for the programmer?
To start off with, don’t try to become an expert programmer/integrator. Get your head around the basics, understand how to monitor and this will almost “show” you what is wrong. By using the monitoring function and understanding both the program and the sequence of the machine, you can quickly follow the program to establish what went wrong.
This leads me to the next thing that our system integrators need to do. When you have a HMI Screen on the equipment, use it to show all components that go into fault status. In other words, write the code so that it will show a limit status, show start failure due to a sensor not being switched etc. Not only will this assist the Electrician when fault finding the machine, it will save a lot of time in getting the fault repaired and being back in production again.
Can I hear someone say this will be too hard? You might be pleasantly surprised. Ladder Logic is actually not that hard to understand. The biggest problem you will face is all the different brands of PLC’s being used as each has their own software and in most cases, this does not come cheap. To use the software you need a licensed/registered copy of the software. Hopefully the site does not have just about every PLC ever made in their cabinets and you can get by with just one software package.
Training is another issue we need to deal with and there are a large number of training packages available. Some of them are very good and some not. Be very careful before you start paying money for this sort of training. Do a bit of research and establish what you want from the training and ensure they can deliver on that.
Till next time, stay safe, don’t take risks and have a productive week!