END-TO-END: The Avnet Total Touch Solution
The touchscreen is often the first point of contact for a customer and the direct interface to gauge customers’ first impressions of the product design and use. Therefore, it is absolutely critical to carefully select the right touchscreen technology for your unique application or design. Touchscreens are defined as a device that allows the user to interact with a display directly. There are more than a dozen touch technologies today. The demand for touchscreens, especially in the industrial and medical markets, continues to explode. The desire for interactivity for the users of LCD devices is now almost mandatory. The touchscreen industry, over the past 2 years, has grown from $4 billion to $13 billion, according to DisplaySearch, and reports have the market increasing to $36 billion within the next few years. This tremendous growth has also required additional capacity for the manufacturing of touchscreens and the actual utilization space will be 16.4 million square meters by 2014.
While certainly some of the significant growth in the overall utilization of touchscreens is attributed to consumer devices, such aa smartphones and tablet PCs – there is also a large and fast growing number of key non-consumer applications such as: ATMs, digital signage, fitness equipment, gaming, hospital bedside entertainment devices, human—machine interface (HMI), kiosks, marine, medical, mil/aero, point-of-sale, vending, and voting machines — to name a few. Each product application has unique technology requirements, value-added service needs, and financial targets to attain. This is why it is critical to gain an understanding of the key attributes available in touch technology.
Touch Technology
Resistive: Resistive touch sensors are simple and reliable. The primary types of resistive plastic overlays are in 4-, 5-, or 8-wire versions. They work via a mechanical function of the top layer being pressed against the bottom layer creating a voltage divider creating an X/Y point. Resistive touchscreens are single-touch products and work in most applications. They are able to receive inputs from almost any input type such as finger, gloved hand, stylus, etc. Resistive is the least expensive of the touch technologies but not the most durable.
Glass Resistive: Many manufacturers are now producing glass-front resistive touch sensors. By laminating a micro sheet of glass to the front surface of a standard resistive product, manufacturers can provide improved protection to the front surface of the sensor.
Resistive Multi-Touch: Resistive multi-touch is similar to standard resistive sensors. The advantage of this technology over standard resistive is the ability to detect dual-touch points. It does this by using a grid of smaller 4- or 5-wire touch sensors or cells.
Surface Capacitive: The majority of surface-capacitive touch sensors are made of glass. A transparent conductor is coated over the surface. When a conductor, typically a finger, comes into contact with the coating, a capacitor is formed which is measured by the touch controller and turned into a touch point. However, surface-capacitive sensors are only able to detect a single-touch point.
Projected Capacitive: Today’s most popular, due to the release of multi-touch products such as smartphones and tablets, is the projected capacitive — a variant of surface capacitive. Although most typically designed with a glass front surface, a projected-capacitive touch sensor can also take advantage of screen protectors, stylized cover glass, as well as vandal or weather-proof glass. A projected-capacitive sensor is manufactured by either a single conductive layer forming a grid or etching two separate perpendicular layers of material forming a grid. Voltage to this grid creates a uniform electrostatic field projected out. A conductive object, usually a finger, breaks the local field at the point it’s touching. The controller detects and measures those points along the grid. Based on the controller programming, a projected-capacitive sensor can detect two or more touch points.
Infrared (IR) Touch: An IR touch sensor utilizes an array of X-Y IR LED and photosensor pairs mounted opposite each other around the edge of the screen. This creates a grid of invisible infrared light. When an object crosses the beam the photosensors are able to measure a decrease of light which is utilized to create a touch-point coordinate. One of the flaws of this technology is the touch frame is above the surface of the display and therefore susceptible to early activation. Infrared is able to perform single touch or multi-touch, depending on the implementation.
Optical Imaging: Optical imaging is a relatively new touch-screen technology. It utilizes two or more imaging sensors around the edge (typically the corners) of a screen. IR backlights are placed in the camera's field of view on one side of the screen. A touch shows up as a shadow and each pair of cameras can then pinpoint the location of the touch and even measure the size of the touching object. This technology is capable of multiple touch points and is scalable to large-format displays.
Surface Acoustic Wave (SAW): SAW touch utilizes ultrasonic waves that pass over the touchscreen glass surface. When the glass is touched a portion of the wave is absorbed. This change registers as a touch event that the controller processes. SAW is capable of understanding nearly any touch object. The disadvantages to SAW technology are its inability to detect a stationary touch point, which is an advantage if resting objects on the screen are to be left undetected. Today, SAW is single-touch with some manufacturers, such as Elo TouchSystems, expanding into two-touch.
Dispersive Signal Technology (DST): DST is a proprietary technology from 3M. It utilizes sensors to detect a piezoelectric change in the glass surface to detect a touch. Similar to SAW, DST is unable to detect a motionless touch point after the initial touch, but is usable with nearly any touch object. DST is a good choice for large-format displays. DST is a single-touch device.
Acoustic Pulse Recognition (APR): APR is a technology introduced by Elo TouchSystems. When an object contacts the APR glass overlay an acoustic pulse is generated. The controller then matches the pulse to an acoustic profile for each location on the glass creating a touch point. Similar to SAW, APR is unable to detect a motionless touch point after the initial touch but is usable with nearly any touch object. It is only available today in finished Elo TouchSystems products. APR is a single-touch device.
Additionally, many of the world-class LCD-supplier partners on the Avnet Embedded line card, such as AUO, NLT, and Sharp, are offering factory-direct, mid-sized industrial display and touchscreen enhancement solutions, mainly around PCAP technology.
End-to-End Solutions
As shown in the illustration below, when selecting touch-screen technology it is important to also consider the entire system-application requirement(s) and needs. This includes evaluating the display requirements, the potential for a Microsoft Embedded O/S license, the embedded microprocessor (possibly Intel based) in a single-board computer product storage, and more.
At Avnet Embedded, we have streamlined the decision-making process by offering an out-of-the-box product that simplifies the evaluation and integration of system boards and LCDs. Performance Matched Kits (PMKs) are the technical alignment of displays and system boards and ensure compatibility between devices. The engineering experts at Avnet address the complex connectivity and firmware issues between these two product sets to deliver a fully vetted set of displays and system-board bill of materials. Related peripheral products and technologies such as touch sensors come complete and are easily adoptable as part of any PMK solution. PMKs, developed using products from industry-leading manufacturers, enable faster application development, speed time to market, and save time and money in logistics and the supply chain for purchasing groups.
Today, there are over 100 touchscreen suppliers in the market. Once the touch technology that closely matches your application requirements is selected, choosing the right supplier is the next step. At Avnet Embedded we work closely with our partners 3M Touch Systems, Dawar, Elo TouchSystems, Fujitsu, and Panjit. All of these touchscreen suppliers have a proven track record of success, high-quality standards, competitive pricing, and offer a variety of touchscreen technology options and from very small mobile products of the 4.3-in. range and upwards of 82.0 in. and above.
At Avnet Embedded, we are uniquely positioned to support most every display, touchscreen, or value-added service request. Our experienced staff of technical-marketing experts provides our customers with working samples, proof of concept, and demonstration units to meet most every display and touchscreen customer request. Our goal is to provide the exact working solution for our customers’ applications and to turn these requests around in a very short period of time. The best way to determine what works best for your application is to utilize actual working solutions and to test within the same environment as the final product will be utilized.
How Can a Customer Learn More about Touch Technology and Avnet’s Solutions?
Avnet Embedded has a team of regional display business-development managers and dedicated technical experts to assist customers during every phase of the design cycle. For more information on display products from Avnet Embedded, e-mail ask-lcd@avnet.com; visit: www.em.avnet.com/embedded; or contact your local Avnet representative.
Joe Fijak is Vice-President of Display Solutions for Avnet Embedded Americas. With responsibility for the sales and marketing of displays and display solutions, Joe has a constant finger on the pulse of trends in the LCD marketplace. Joe is an industry veteran, with more than 30 years of experience in electronic distribution and 20 years dedicated to display and embedded product sales. Joe joined Avnet Embedded in January of 2010. For more information on display products from Avnet Embedded, visit:www.em.avnet.com/embedded.