Thinking about HMI projects

You need an operator Interface for your machine. You have some ideas about what you want it to do. You begin to search the market for an appropriate HMI that fits in your panel. Then the frustration begins. Not all HMI's are created equal. Some will do what you need and others won't. Finally you find one that looks like a good prospect. Only to find out as you go along, that more features are needed than the HMI can handle. Specifications get changed by end customers. Suddenly the deadline to finish the project looms large!  Despite all of the planning to try and diffuse this situation, it arises anyway.

All too often the HMI programmer is stuck between Supervisor and Customer demands. Much of this can be avoided with some pre-planning. Like all engineering, design before doing/making is the best way (if you have time!).

First determine if a Panel PC with HMI software might be a better choice than an embedded HMI platform. I have experienced disillusioned customers that thought embedded HMI panels could do everything a panel PC could do. (Like, run 3rd party applications, store GB of information, show a spreadsheet with pie chart or show 16 different windows at the same time. Really?) I know embedded HMI's are getting better all the time, but they are not quite there yet.

Use a Panel PC if you are going to use the interface as a data gathering tool. A 1.5TB hard drive will hold more process data than you can view in a lifetime. Unlimited Trending and Event Tracking are good reasons to use a Panel PC. There are a lot of graphic libraries for PC's so every screen can look pretty. PC's can also be setup as a website for other PC's to view their data.

Use an embedded HMI when operator control is a high priority. Most HMI's can handle several communication streams to provide control for several PLC's. HMI's can handle some data logging and Event/Alarm logging, but, even with external memory sticks the data can be limited. Embedded HMI's have no fans or hard drives to fail and are more rugged for industrial situations.

The best solution is to call the provider of Panel PC's or embedded HMI's and talk to them about the application. They can usually guide you as to which platform is best for your application.