Advertisement
Articles
Advertisement

The Use of Touch-screens in Industrial Applications

Wed, 12/01/2010 - 4:30am
Simon Wyre, Lascar Electronics, www.lascarelectronics.com
Simon WyreAutomation in the workplace has been rising from the middle of the 20th century, with the introduction of the microprocessor in the 70’s fuelling a massive increase in the use of electronic devices to measure, monitor and control industrial processes. Although the user had interacted with such devices using mostly switches, their use become more limited as the complexity of data exchange went up and graphical screens were employed in an ever greater number of applications. Initially, users would interact with such systems with a keyboard and possibly some sort of pointing device such as a mouse but both have many disadvantages, not least of which is their poor reliability in an industrial application.

The alternative is the touch-screen, technology which is increasingly becoming the natural choice for interfacing with industrial machines, right down to the smallest of displays.

What is “Industrial”? An industrial application can mean any application which is in a harsh environment and not just controlling a milling machine on the shop floor. Such applications include:-

• Point of Sale devices like checkout tills
• Interactive display systems such as shopping mall information screens
• ATM and public transport ticket issuing machines
• Gaming machines in public areas and amusement arcades
• Marine and offshore installations
• Aerospace
• Road transport
• Industrial process control

Although touch screens have been around for about 40 years, their high cost limited their uptake to more expensive applications. As cheap touch screens pervaded the consumer market in the last ten years, their cost has come down considerably and that has led to more touch screens being designed in to industrial units.

The main selling point of the touch screen is its ruggedness but the advantages of the industrial touch screen do not begin or end there. Other benefits of touch screens in industrial applications include:-

• Simple interface. With only the screen to deal with, the user is less likely to make mistakes. They can be guided by on-screen menus. If a switch must not be pressed, don’t put it on the screen. This is especially true for casual and non-technical users such as shoppers. On the shop floor, this should lead to an improvement in safety and productivity
• More reliable. Keyboards can have over 100 switches. The touch screen has no moving parts
• Less space. This is particularly important in places where space is limited, such as the driver’s cab or the pilot’s cockpit
• More portable
• With no need to print on or around any keys or switches, it is much easier to make the system multi-lingual
• With a keypad or keyboard, the switches are in a fixed position but the touch screen can have any shape and size of ‘key’
• Resistant to contamination. They are impervious to dust, chemicals, fluids and the weather
• Will not contaminate. Especially important in the food processing industry or silicon foundries
• Combined with RFID for security tag or credit card processing as required, the system can be completely sealed
• Resistant to vandalism or heavy use
• Can be used in hazardous areas like mining or petro-chemical industries

There are a number of touch screen technologies available to the designer and it is important to match the technology to the application for optimum performance and cost-effectiveness. The following list is not exhaustive but covers the main types:-

Panel PilotResistive:

The most widely type used in small - medium devices and mobile phones. It is cheap, has a low activation pressure and can be used with most pointing devices and is well suited to small applications. Its disadvantage is that it reduces light transmission by about 25%. If precision is required, it will need periodic re-calibration and can eventually wear out. The plastic top layer is not very scratch resistant.

Capacitiative:

Uses glass on the top layer and is very scratch resistant with excellent light transmission. This display uses static to detect the presence of a pointing device but not if it is insulating such as a gloved hand. The most popular choice for kiosk and ATP applications

Surface Acoustic Wave (SAW):

Uses sound waves to detect the presence of the pointing device. Uses glass and like the capacitiative system, has a high light transmission. It is, however, badly affected by surface contaminants and has limited operation with pointing devices other than human fingers. Another popular choice for ATM applications

Infrared:

A ‘screen’ of infrared is cast over the display and where the pointing device interrupts it, its position can be determined. It can work with any screen type and has zero activation pressure. Light transmission is excellent but the resolution is lower than other technologies. Can be affected by extreme levels of contamination. Needs a large overlay frame, which can be intrusive with small screens.

It is important for the designer to study the advantages and disadvantages of the different screen types before integrating one into their product but once mastered, it will reap benefits for them and their customers. The touch screen is now the interface of choice in many industrial applications and is displacing conventional input devices. As its cost continues to fall, so will it find its way into smaller and simpler systems. With suitable software, its operation is easily understood by technical and non-technical alike and has a more natural operation than the separate data entry and pointing devices found on conventional PCs.
Advertisement

Share this Story

X
You may login with either your assigned username or your e-mail address.
The password field is case sensitive.
Loading