Things have changed a lot since I started in this business. In the “old days”, you could use any color combination you wanted on your HMI screen, as long as it was amber on a black background. You could use timers and counters in your ladder logic, as long as they were structured exactly right, and outputs always went at the end of the rung. Always.
Times have changed. The products we use today offer the programmer an incredible amount of flexibility in how we conduct our craft. The color palette we can use on our HMI screens is not only extensive; we can create our own colors if we want. We can make things change colors, change shapes, change positions, disappear and just about anything else we can dream up. In our ladder logic, we can create rungs of tremendous size and complexity and yes, we can even put our output coils in the middle of the rung if we want to.
As a System Integrator, I think we have a responsibility to use our tools wisely. How can we best present information to our HMI user so that can determine the necessary action to take in any given situation? Is the information clear and concise, or do they have to sort it out amidst all the colors and moving symbols on the screen? Can the plant’s maintenance staff go into our ladder logic and quickly determine the issue that is preventing production at 2am or do they have to try to sort through complex logic filled with indirect references?
I submit that simpler is better. Just because you can, doesn’t mean you should.
What do you think?