"It is impossible for ideas to compete in the marketplace if no forum for
  their presentation is provided or available." �        �Thomas Mann, 1896

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THE USER INTERFACE

Author: Hemant Mistry
Contributed by Jayco Interface Technology Inc.

Look at any electronic device, whether it is a stereo amplifier, photo-copier, laboratory or test equipment, and aside from its overall form, what first strikes you is the control panel or user interface. Most people react emotionally on first viewing � " I like it" or " I don�t like it". If you are the manufacturer or reseller of the product - you have either just pre-sold your product, or you have turned your customer off.

In today�s instant gratification culture with the 10-second sound bite and the 3-second web page scan, emotions and opinions are formed on the most fleeting snippets of information. Value judgments are made and all information subsequently gathered serves only to reinforce the original perception. Thus if you don�t get immediate buy-in from your prospective customers you face an uphill battle trying to overcome their initial prejudice.

Design for emotion!

Beyond appearance come the touchy-feely aspects. A product has to look good, but it must also feel good. Your customers will evaluate the texture and the tactile qualities of your product. Does it feel cold and hard or warm and inviting? If they see and "feel" quality on the outside they will assume there is quality on the inside. And vice versa, if they think you have skimped on the outside where it is obvious, what must you have skimped on the inside where all is hidden? Don�t believe it? Ask yourself why car manufacturers pay close attention to the grain of their leather and vinyl, or why Mercedes-Benz "engineers" the sound of their doors closing and the way their turn signal stalk feels.

How do you begin the design process?

The design process begins with a review of the project. Consider the application � how will the product be used, what environment will it be used in, what is the purpose of the panel, what image do you want to project, and what is your budget?

Application and environment

Be prepared to offer as much information as you can to your control panel supplier. If it is impossible to reveal the nature of the product without breach of confidentiality, by all means work under a non-disclosure agreement. Most companies in this field are highly professional and experienced in working on sensitive projects. Specifically, you need to answer the following questions:

1. What is the application for the product? What is its end use? If you cannot reveal specifics, talk about similar products, e.g., a data collection device, hand-held, used by trained users. Perhaps it is a medical device. You may not want to reveal that it is for a revolutionary procedure that will make angioplasty obsolete, but you can say that it will be used in an operating room; that the displays need to be read from across the room, or that the switch operating pressure must not exceed 100 grams, etc.

2. Who will be using the product? Are they trained or untrained? This can affect layout, the number of buttons, menu structure, and influence which control panel technologies are appropriate.

3. How and where will the product be used? Will it be subject to abuse? Is the product going to be used indoors or out? Will it be exposed to harsh chemicals? High altitude, extremes of heat and cold, humidity, shielding and sealing requirements, shock and vibration all affect how the product must be designed and manufactured, and the materials to be used. Consider all the environmental conditions the equipment will face.

4. When will it be used, how often will the switches be pressed? Is the device a set and forget piece of equipment, or will it require constant monitoring? Is data input required frequently? Are the displays used for programming? What alarms conditions need to be signaled?

These questions are typical of the data collection process you must go through to help you characterize the application and find key elements essential to the success of the product. The answers also help determine materials to be used, construction techniques, and other engineering constraints that begin to influence cost even before external design options such as size, number of colors, tactile or non-tactile switches, etc are considered.

Purpose and expectations

Ask yourself why you need a control panel. This may seem obvious but the control panel is the interface between people and machines. It is a communications device. It enables two way communication of information between the user and the equipment. But what is the primary function of your control panel?

1) Is it to give information?

2) To collect data?

3) To help control operations?

Either approach is valid. But the brief should be appropriate for the application and the market you are targeting.

Who should do the design?

If you follow this methodology it quickly becomes apparent that you need to select your designers and control panel supplier before putting pen to paper. Early involvement is critical to ensure the best panel for your product, and to avoid and eliminate potential problems. Likewise, close cooperation between the designer and the control panel supplier is essential to ensure all ideas are thoroughly explored and manufacturing issues are considered in the design. Designer and control panel supplier must work hand in glove with your engineering department. Seamless open communication, and trust and respect for each party�s expertise lead to best results.

What technologies are available?

There are four primary control panel technologies � traditional, membrane, silicone rubber keypads, and touch screens. Although any of these can be used in most applications, careful review of your project and a thorough knowledge of all the available technologies will usually help to point toward a particular approach for any given application.

Traditional

Mechanical switches mounted onto a metal or plastic panel. Holes are cut out in the panel for switches and displays to poke through. A variation is where switches are soldered directly to a PCB and keycaps are used. It can be suitable for both high and low volume applications, and is a very versatile technology enabling very up to date designs or even providing a certain "retro" appeal.

In high-end audio for example it�s the predominant choice. In others like bench-top analytical instruments, e.g., oscilloscopes, it is still quite common although membrane and SRK technologies are becoming more popular.

Membrane switches

These are very low profile switches first used on high volume applications like calculators and microwave ovens. Although membrane switches started out as low cost, low-end devices, they quickly moved up-market and are now commonly used on everything from office equipment to medical instruments to military and satellite navigation equipment. In 20 short years the use of membrane switches has grown to approximately 40% of the switch market.

The rise in popularity of membrane switches can be attributed to their low cost, design flexibility, versatility, and reliability. Other than pure data entry such as computer keyboards, there are few applications where membrane switches are not appropriate. And although computer keyboards do not use membrane switches to provide feedback to the user, most computer keyboards do in fact use membrane circuits to carry the electrical signals back to the encoder.

Another reason for the popularity of membrane switches is that they can be made to work in almost any environment. Properly designed membrane switches will prove reliable even in very harsh environments. Despite early impressions of membrane switches, they last a long time. Life cycles are typically 10 times normal mechanical switches. However, poor manufacturing and process controls can reduce membrane switches to junk status. That�s why it is so important to work with someone who really knows what they are doing, and not judge them simply on price or by one or two samples.

Silicone rubber keypads

These are really a variation of membrane switch technology, even though they are made using completely different processes. Silicone rubber keypads (SRK) have characteristics of both membranes and traditional mechanical switches. In the finished application they can look like mechanical switches but have the cost, reliability and design versatility of membrane switches. Recent developments have focused on special coatings to improve abrasion and chemical resistance as well as providing aesthetic design options.

The earliest applications for SRK were for calculators and remote controls. With improved materials and process controls leading to greater reliability and durability SRK are now found on all kinds of electronics equipment ranging from cellular phones to laser guided targeting systems.

Touch screens

Touch screens employ a variety of different technologies to achieve the same purpose � to allow displays to function as control panels. A touch screen is basically a transparent switch placed over or around a display. Touch screen technologies include resistive, capacitive, acoustic wave, and strain gauge, among others. Each has its own associated set of pros and cons and none is "better" than the other. But the most popular is the resistive touch screen, which basically is a transparent membrane switch. Primary reasons for the popularity of resistive touch screens is their low cost, easy integration and versatility of use.

To date touch screens have been expensive solutions to control panel problems, but in many applications they are the most suitable approach. As microprocessors and software become cheaper and more powerful, the use of touch screens will grow. More complex instrumentation calls for simpler ways of interfacing with equipment. In those cases touch screens are often the best solution.

Where do you go from here?

Your best results will be achieved by doing your homework before you finish the design of your product. Investigate a few companies, test their capabilities, and select one you feel comfortable working with. Then make them your control panel partner and involve them as early as possible in the design of your product. A good supplier will help guide you through the development process and avoid pitfalls and dead ends. They will help reduce development times and get your product to market faster. Remember that you are not just buying the physical product they will make for you. You are buying their expertise, you are buying their ideas, their project management skills and their commitment to you and your success.