Designing a Touchscreen: Where to Begin

Touchscreens are gaining popularity with manufacturers as an alternative to other switching technologies, and it is easy to see why. When it comes to user interfaces, touchscreens have successfully changed the way electronic equipment is used by simplifying the user experience and eliminating the need for buttons or keys. If you are considering incorporating a touchscreen into the design of your product, there are key items that you should consider.

First you should understand the difference between a resistive touchscreen and a capacitive touchscreen.

Resistive TouchscreenResistive Touchscreen Illustration

A resistive touchscreen is constructed using two clear conductive layers (typically a glass or acrylic substrate and a polyester top sheet) that are separated by insulating dots. When the user touches the screen and compresses the top flexible layer, electrical contact occurs between the top and bottom layer.

Capacitive TouchscreenCapacitive Touchscreen IllustrationRGB

Voltage is applied to the corners of a capacitive touchscreen and distributed by a pattern of electrodes located around the touchscreen periphery. This creates a uniform electric field across the conductive surface. When the user touches the screen with a conductive object (such as their finger), they are drawing a minute amount of current from the surface. This change in capacitance is measured at each point on the touchscreen allowing the touch position to be located.

Before you actually sit down and design your touchscreen, there are at least four main considerations you need to take into account:

  1. Environmental conditions
  2. Software requirements
  3. Firmware requirements
  4. Appearance

These will help you determine the materials and types of technology to utilize in your touchscreen. For each consideration there are a number of questions you will need to ask yourself:

Environmental Conditions

Will my touchscreen be locatediStock_000009292698Large indoors or outdoors? The location of your touchscreen and the environmental conditions it will be exposed to determine the type of material that should be used and if any coatings need to be applied. Different types of glass and plastic can be used as a cover lens for a touchscreen. Glasses include:

  • Soda lime
  • Chemically strengthened
  • Tempered

Examples of plastics that are typically used are:

  • Polycarbonates
  • Acrylics

Will it be exposed to harsh chemicals/weather/punishment? If your touchscreen will be exposed to harsh environments, hard-coats can be applied to add durability. The performance of resistive touchscreens is not impacted by liquid; however resistive touchscreens are more prone to damage than capacitive touchscreens, which can handle many environmental extremes.

What will the lighting be like in the area my touchscreen is located? Will it be exposed to UV light? If your touchscreen is made of glass or another reflective material and will be in an environment exposed to high amounts of natural or artificial lighting, coatings can be applied to increase readability including:

  • Anti-glare
  • Anti-reflective
  • Polarized
  • UV resistant

Resistive touchscreens tend to have lower optical clarity than capacitive touchscreens, which are known to have superior optical performance.

Will my touchscreen be exposed to EMI? Capacitive touchscreens are susceptible to EMI.

Will the users be using their hands/gloves/a pointing device? Resistive touchscreens are compatible with any pointing device, including gloves. Capacitive touchscreens can be operated with a finger, conductive gloves, or an active stylus.

Software Requirements

iStock_000007759510LargeWhat will my touchscreen be used for? If your touchscreen is going to be used in a fast-paced environment, you want to make sure the interface is as user-friendly as possible so the user can navigate through it quickly.

What types of menus and interfaces are needed? If the users have large protective gloves on, the buttons and menus should also be large to accommodate that. Capacitive touchscreens are highly accurate compared to resistive touchscreens, and they also possess multi-touch and gesture capabilities.

Firmware Requirements

What will my touchscreenVoting on Touch Screen be used for? Is it important that the response time is as quick as possible? Your touchscreen should include a fast interrupt-driven processor that responds quickly to the user if it is to be located in any type of fast-paced environment. You will also need to factor in a controller, which is a device that interfaces with a peripheral device if you are using a resistive touchscreen.

Appearance

iStock_000019825647LargeWhat will the screen size need to be? Screen sizes for resistive touchscreens typically range from 2.2”-22”, while screen sizes for capacitive touchscreens typically range from 3.5”-17”.

How should the touchscreen feel to the user? Resistive touchscreens would have a polyester top sheet, which has a very different look and feel compared to the solid glass panel of touchscreens. The flexing of the top layer of resistive touchscreens can also cause noticeable wear over time.

Is it important that my touchscreen is easy to read? Resistive touchscreens have lower optical clarity, and capacitive touchscreens are known for their superior optical performance. However, because capacitive touchscreens are made with a glass panel an anti-glare or anti-reflective coating may be required in a brightly lit area.

While these considerations are a good place to start, each project is going to be completely different from the next. There may be other considerations that come into play like pricing or product integration, and with custom touchscreens you may not know the extent of what is required for your design until you start going over it with your manufacturer. Don’t be afraid to work through these obstacles with them and listen to their suggestions. Chances are that they have seen your problem before and already know of a good way to solve it.

For more information on custom touchscreen design, along with a glossary of commonly used terms, download our full Touchscreen Design Guidelines.


Wilson-Hurd, founded in 1904, offers custom printing, fabricating, and electronic manufacturing services, and is a top manufacturer of electronic control products, printed electronics, POP displays, medical contract manufacturing, and nameplates & dials, overlays, and panels. To learn more about Wilson-Hurd, please visit our website at wilsonhurd.com.

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