+46 18 660 700
Would you like to be contacted?
Quarterly Bulletin
 
 
Industrial PCAP touch screen technology
 
 

The majority of touch screens of today use one of two technologies – Projected capacitive or analogue resistive. More and more designs, also in embedded computing, choose the projective capacitive technology, PCAP, to turn the surface in front of the display into a modern user interface.

 
An important reason for the trend is that PCAP is widely used in smart phones and tablets. Industrial computers and embedded systems thereby make use of new and extended ways of user input and control by touching and pointing, with one finger or more, rotate, zoom and moving objects on the display. Consequently industrial embedded products are adapted to modern user behavior and benefit from the look and feel of the latest mobile gadgets.

The analogue resistive touch screen technology was launched about 20 years ago. It’s the cheaper alternative of the two today. The pressure sensitive surface reacts to touch from a variety of objects such as a finger, with or without thick gloves, pencils and tools. For these reasons one or another product will definitely use the resistive touch technology, now and in the future, but the trend is in favor of PCAP. Let’s have look at the advantages!
 

Protective shielding and extended operating life

PCAP is the alternative with the highest light transmittance in comparison and the best image clarity. Almost none of the light is blocked when the PCAP touch screen is mounted in front of the display. The resistive technology suffers from reduced light transmittance in comparison with PCAP and therefore decreases the sought-after brightness of the underlying TFT-LCD.

A direct contact between the finger and the PCAP touch sensitive surface is not needed for operation. A glass plate may be mounted as an outer transparent protective layer without interfering with the touch functionality. The choice of material and thickness of the plate may even protect the system from vandalism in public places. It’s worth mentioning that the operating life of the touch screen generally is well over the operating life of the display.
 

Introducing multi-touch gesture control

Yet another advantage of PCAP over the resistive technology is the possibility of using so-called multi-touch gesture in the user interface. It’s the input method familiar to more and more people since it’s widely used in smart phones and tablets. The picture at the beginning of the text gives you an idea of what multi-touch gestures are, or actually more correctly, dual-touch gestures since no more than two fingers are involved.

The principal of the PCAP technology is based on two electrode leader layers, in rows and columns, mounted with a separator in between. An electric field is created on one of the electrode leader layers. The capacitance coupling is measured for every x/y electrode intersection, one by one, as the controller scans the surface.
 

Scanning the capacitive coupling

A finger touching the surface will affect the capacitive coupling between the two layers in the touched spot. The coordinates of the touching finger will be calculated by the controller from scanning the surface.  Triangulation using the information detected in a number of x/y intersections improves the precision. The touch and movements of the fingers on the screen are translated to gestures and input by the operating system and application software.
 
The PCAP technology allows the electrode layers to be fully protected by glass plates since direct contact between the finger and electrodes is not needed to trigger the touch functionality.
 
The capacitive coupling between the horizontal x electrodes (red) and the vertical y electrodes (blue) are scanned to detect touch.
 

Bonding the display and touch screen

Calibration of the touch screen and display is made once and for all in production of the product. Coordinate drift thereafter is non-existent since the touch coordinates are measured scanning the physically fixed grid of electrode intersections. The finger touch on the screen is detected with precision, year after year and in a wide range of operating temperatures.

The touch screen is attached to the display either by edge bonding or optical bonding. The downside with bonding only the edges of the touch screen and display is the inevitable air-gap between the two surfaces in between the bonded frame. Dust and condensation of water in that gap decrease image clarity.

Light travelling through the internal layers will induce reflections as a consequence of the air gap. This leads to glare and decreased optical properties not the least in direct sunlight. Edge bonding is the less costly bonding option of the two. Touch screen and display edge bonded are quite easily dismantled during service and repairs to replace one or the other.
 

Edge bonding:

When light travels through material layers and pass from one material to another with different refractive index (for instance glass to air or air to glass) reflections are generated.

 

Optical bonding:

The refractive indexes of the glass and adhesive are matched to reduce reflections and increase image quality.

 

Improving image clarity with optical bonding

Optical bonding is made using an adhesive that has the same (or close to the same) refractive index as the glass. Reflections are thereby kept at a minimum and the visibility is increased. It’s the preferred way to bond the touch screen and display in applications to be used outdoors and in direct sunlight.

Optical bonding also increases the strength of the surface and the glass is less likely to break when operated by the sometimes rough citizen using applications like for example digital signage, point of sales or information or kiosks. Optical bonding is more costly than edge bonding. The bond can be dismantled but it’s complicated and takes time.

Hectronic sell industrial displays, touch screens and controller boards. But more importantly we offer the complete display solution including TFT-LCD module, touch functionality, bonding, calibration and cables to be integrated in your industrial embedded product. The display and touch screen products and integration services described are a part of the extensive embedded system development offer that are described on the website and offered to customers for more than 20 years now. 
 
 

PCAP touch screen products from Hectronic

Hectronic introduces a series of industrial touch screens based on the PCAP technology. Sizes range from 5.7 inch to 15 inch. A controller board with an ASIC detects the touch from one or two fingers (dual-touch) of the user on the screen and assists in converting pointing, touch and movements on the screen to system input data.

The PCAP touch screen solutions offered by Hectronic are protected by glass to withstand harsh environments and for maximum light transmittance. Water proof solutions are an option. The glass surface withstands various chemicals, for instance strong cleaning agents, which is not the least important in medical applications where hygiene is a top priority. The user interface is accessible with thin gloves, like for example latex gloves, and the controller distinguishes between water drops on the surface and the touch of fingers.

The touch screens are offered in a range of sizes. Should the particular size you are using not be represented in our standard product offer there is always the custom option to be considered. The annual volume required to motivate the NRE for development of a customized touch screen may well be acceptable.

 

Touch screen product group » 

 
 

The EXC Projected Capacitive Screens offered by Hectronic use transparent electrode technology which allows two points/fingers (dual-touch) recognition and light touch inputs.

Touch screen product group »

 
 
EXC7200 series is a controller board that works as a generator of coordinates for EXC Projected Capacitive Screens. USB and RS232C are supported.
 

General technical specifications for EXC Series of touch screens

Operating Life
Surface Hardness
 Light Transmittance
 Reflectance ratio
 Operating Temperature

Matrix numbers

 

Over 50 million touches
6H
Over 90%
Less than 8%
-20°C to +70°C
X axis 30wire Y axis 23wire /8.4inch
X axis 52wire Y axis 40wire /15inch
 

Table of drivers to support the use of EXC Projected Capacitive Screens

Interface

USB
 
 
 
RS232C
 
 
OS drivers
Windows 7 HID digitizer driver
Windows Xp and Vista
Linux
Android
Windows Xp and Vista
Linux
Android
 

Market segments

Meeting requirements from industry sectors.
 
Learn more

Technologies

Promoting a deeper understanding of technical possibilities at hand.
 
Learn more

Case studies

Development and production for industrial customers.
 
Learn more

Bits & Pieces bulletin

Technical articles, inspiring case studies product news and updates. B&P is distributed quarterly to registered users.
 

Subscribe

Enter your e-mail address and click subscribe.
 
 

Products

Technologies
 
Find us on
 
 
Hectronic AB | Phone: +46 18 660 700 | E-mail: info@hectronic.se | Sitemap | Cookies
© 2017 Hectronic