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Custom User Interfaces Vs Programmable Logic Controllers

Ed McMahon
Written by Ed McMahon
Posted on May 18, 2016 at 12:44 PM

There is good reason that programmable logic controllers (PLC) are used as a user interface in a large number of applications. These robust devices are commonplace on factory floors controlling equipment, in processing plants monitoring operating conditions, and even used in portable devices exposed to harsh environments.

Low volume PLCs and one-off applications are expensive and limited devices but are preferable because they are simple to program and have a built-in operating system so development costs for the controls are minimal.

However, with the advent of low cost touch screens, LCD's, LED's, and software/firmware operating systems, more OEM products are moving towards custom devices for their applications. This is especially true in the medical and industrial industries where the volumes are several hundred to several thousand per year. While the upfront development costs are much higher the price per piece of the user interface assembly when completed can be 10x less than a standard off-the-shelf PLC.

Smart HMI Control Panel

Smart Human-Machine Interface Control Panel

New Human-Machine Interface Technologies

Using new materials, components, and software technologies, the best companies can design and manufacture to exceed applications requirements. There is more involved than just creating a standard membrane switch or other low technology solution. These manufactures can create full assembly smart interface products that can read inputs from various sources to develop a much more custom experience for the end user.

With new human-machine interface (HMI) technologies such as light guide panels and side firing LEDs can be custom programmed to assure that the user is promoted to operate your device in the correct way. This in turn reduces customer support required, warranty issues, and improves overall customer satisfaction. Having been a designer and manufacturer of these products for over 25 years, our experience shows that we can develop these custom user interface solutions for any application, regardless of the operating environment that it will be used in.

Cost Factors of Custom User Interfaces

The question that always comes up is: How much will it cost? With all of this customization the assumption is that it must be hundreds of thousands of dollars to design one of these smart interface products. Especially when you take into consideration the electrical and mechanical design, hard tooling, PCBAs, touch screens, etc. While there is an up-front cost with the development, it is not as much as you would think and will usually pay for itself quickly with the reduced cost of the end product.

For example, we recently manufactured a smart interface that included:

  1. Ability to read inputs from 12 different sensors.
  2. Creation of firmware and software for 65 different screen shots on the LCD.
  3. A rugged switch and bezel assembly that would be need to be water proof.
  4. A lighting scheme that included custom programming and 4 different colors for each button.
  5. Completed and functional prototypes.
  6. Full mechanical and electrical drawing packages.

All of this was completed in 7 weeks for about $40k. This is a great value when you look at the production costs. The clients estimated annual usage is 500-pieces a year. The lowest end PLCs go for $350 which would cost the company $175,000, whereas the end product from our development was only $98 each for 500-pieces. This turns out to yearly savings of over $125,000. This is certainly a quick payback of the initial $40k.

It is critical in these situations to work with a supplier that have both the design and manufacturing capabilities in-house. This keeps the development cost to a minimum as these companies are more interested in making their profit by producing parts and not marking up the design. In many instances they will even amortize the development costs into the piece price if the opportunity is large enough.


With the inclusion of new hardware and software developments happening every day, the cost of designing and building custom solutions for any user interface continues to go down. Lower cost gives companies opportunity to ensure that their user experience is first class and can separate them from the competition. With custom user interfaces incorporating superior technology and compatibility compared to PLC, the advantages are clear. 

Topics: User Interfaces

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