In this article, PLCGurus.NET member John C. Jones shares his insight and learned best practices for those readers just getting started into the field of Industrial Automation and Control System Design. Whether you’re fresh out of school or looking for an entry point into this exciting career, John’s experience shines through as he authors this Guide To Success For Young Controls Engineers. Enjoy!
“Rules of engagement – Rules of engagement do not normally dictate how a result is to be achieved, but will indicate what measures may be unacceptable.”[i]
Tools you will need
A brand new spiral college ruled, 100-page notebook.
I cannot emphasize the importance of keeping good notes. This should start day one of the project. Keep the notebook with you at all times. Partition the notebook into categories. Organize, organize and organize.
- Meetings with the production manager, manufacturing engineer and maintenance technicians
- Variables lists, instructions list (PID, Block Moves, Temperature control), sequence ideas and code examples. If you need examples, I use materials from http://www.industrialtext.com/freestuff.htm.
- Protocols you will be dealing with such as Modbus RTU, Modbus TCP, Profinet, Profibus, etc.
- Hardware needed. Input modules both digital and analog, output modules both digital and analog. Special cards needed, High Speed counters, high density, power supplies, relays, etc.
- Schedule. Make a good schedule based on the time frame given and when run off is scheduled.
- Specialized notes, etchings, do not forget items and ideas.
Why not use MS Excel for all of this? This will come later in the project. Paper and pencil please.
A good quality digital camera
This is a very good tool to have. Get one that will record video as well. You will use this at the install site as well at your office for reference. Take pictures of existing control wiring, conduits, plugs, safety signs and floor space.
Electrical and Mechanical CAD software.
The software you use will more than likely be dictated by your employer. If not, I recommend the Autodesk line such as ACAD Electrical and Mechanical. If you need training on any of the aforementioned hardware or software, stop and tell your boss immediately. Not doing this can be deadly.
Your thick skin
Yes, you become the middle man between production and your department. Dealing with people is a real skill. Schedules change. People leave. Some people will resist everting about the project itself. Stress levels reach new highs. All hands-on deck. Steady as she goes captain.
I am going to guess that your project will be implemented in an automated cell already. You will have to interpret the existing code in the master controller and more than likely a Programmable Automation Controller (PAC ). You will be handed the original electrical diagrams and PAC Project. Make sure that the electrical diagrams are accurate and with all the revisions. This is a wreck waiting to happen if they are not up to date. Go online with the master controller and download the program for yourself. Contact your Facilities Electrical Engineer for up-to-date electrical diagrams. There is a better than 50% chance you will not get the support you need.
Everything is visual for me. In the automated world today, multitasking is a true art form. When I am writing the control code I have to be alone and with no distractions. Time and time again you can write code and say to yourself “This will work great” only to find out it does any thing but what you thought.
Simulators are good but are extremely limited.
Hats you must wear
The controls engineer must have a working knowledge of pneumatic principles, devices and diagram interpretation.
He or she must have a working knowledge of industrial hydraulics, servo motion, variable frequency drives, mechanical systems such as gear reduction, active electrical devices and safety regulations.
Standards, NFPA, IEC and all safety regulations for industrial systems.
Communicator. Be a good communicator. Master the art.
Training the maintenance technicians on troubleshooting the system is a must.
Most of all you need to have a good understanding of the systems and the code of the other machines you are going to be dealing with – you cannot control a system if you don’t understand what it is you’re trying to control.
Finally, Normalizing your code
No one ever programs the same. Be consistent, and pretty soon the personnel that have to troubleshoot the system start to characteristically become better at what they do also. After all, you don’t want the system to be down for hours for a faulty limit switch or solenoid valve. Create troubleshooting guides and operation manuals if need be.
Through my thirty plus years, I have seen some really well written PLC programs and then again, I have seen some I thought were written by the devil himself!
Make your code understandable, and structured. It will not matter which language you use, Relay Ladder Logic, Statement language, User Listing, Flow blocks or C. Comment your program until it borders ridiculous.
Segment your program into subroutines for each piece of equipment you are controlling.
Avoid using set and reset coils or latch and unlatch coils. This is the lazy programmers tool. If this is unavoidable keep the two coils together. Do not put the reset coil far away from the set coil. Maintenance technicians will sing and dance at your wedding. You can write a great and robust program without these.
Avoid large OR rungs that cannot be fitted on the computer screen or on a printed page. Use a negated coil instead and create a simple series rung that can be seen on one screen. Maintenance technicians will mow your grass each week. Many times, these are used for alarming.
Avoid jumps in your code at all cost. Don’t need them.
Do give your variables good names and descriptions.
Do have a good cross reference in your PAC project.
If the CPU has the ability to run UDFB’s (User defined function blocks) then create them, use them and document them. Save these to your library for future use!
These are just a few things to master with many more to go, like building your electrical cabinet, safety, safety and more safety. Your library collection and all these topics will be saved for another discussion.
This sounds very intimidating, but just be self-controlled and straight forward with everyone you deal with. Doing this will make life in this job easier and rewarding.
“Social philosophers early reflected on this idea by advocating the usefulness of knowledge in human endeavors. In the late sixteenth century, Francis Bacon, regarded by many as the father of scientific methods of inquiry, was more specific. Bacon said, “Knowledge is power.”[ii]
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