Introduction 2. The Base of Projected Capacitive Touch 3. How Projected Capacitive Works 5. Types of Projected Capacitive Touch Screens 6

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1 Whitepaper

2 Contents Introduction 2 The Base of Projected Capacitive Touch 3 How Projected Capacitive Works 5 Types of Projected Capacitive Touch Screens 6 Advantages 9 Disadvantages 11 Cover Lenses 12 Typical Applications 13 Whitepaper The Projected Capacitive Touch Screen Handbook 1

3 Introduction It was only 10 years ago that one of today's most used touch screen technologies was just an obscurity. Projected capacitive touch screens are in the top two most used touch screen technologies. Right after resistive touch screens. Projected capacitive (PCAP) touch offers many great advantages over the more traditional touch technologies. There is a reason why Apple chose PCAP touch technology for their iphones. But it's not just the consumer industry that has grown fond of PCAP touch technology. The healthcare, industrial and automotive industry are also among PCAP's newest fans. Over the last couple of years we have seen a steep increase in the use of projected capacitive touch screens. That is why we have put together this summarizing article on PCAP touch technology. So let s dive in! How does PCAP touch technology work? What benefits does this touch technology offer? Are there any disadvantages? And what applications make perfect hosts for projected capacitive touch screens? Want to compare Projected Capacitive Touch Screens to other touch technologies? Download our Free Touch Technology Comparison Chart. Whitepaper The Projected Capacitive Touch Screen Handbook 2

4 The Base As the name might suggest, the base of projected capacitive touch screens lies with capacitive touch technology. For a long time capacitive touch screen technology was the second most popular touch screen technology out there. Following resistive touch. E.A. Johnson designed this touch technology in the 1960's. Many consider it to be the first touch screen technology ever discovered. [ Further Reading The History of Touch Screen Technology ] Capacitive touch screens are the foundation of projected capacitive touch screens. Capacitive touch screens use a transparent electrode layer. The electrode layer is placed on top of a glass panel and Whitepaper The Projected Capacitive Touch Screen Handbook 3

5 eventually covered by a protective layer. A touch is detected when a touching finger transfers some of the electrical charge from the screen to the user. Sensors in all four corners of a capacitive touch screen detect the drop in electric current. The touch screen's controller then detects the touch. Capacitive touch screens do have two major disadvantages though. They only work with a bare finger or a special capacitive stylus. This eliminates use of capacitive touch in environments where gloves are worn. Think about heavy industrial environments or an operating theatre. Next to that capacitive touch screens don't allow multi touch. Thanks to tablets and smartphones, multi touch and gesture touch are becoming more intuitive every day. So not have these functionalities could be an issue. These two downsides have resulted in the development of PCAP touch technology. What's the difference between capacitive and projected capacitive? Whitepaper The Projected Capacitive Touch Screen Handbook 4

6 How Projected Capacitive Touch Screens Work In essence PCAP touch technology is similar to capacitive touch screen technology. Both consist of a sheet of glass with embedded transparent electrode films and an IC chip. This composition creates a three dimensional electrostatic field. A capacitive or PCAP touch screen detects a touch when a touching finger changes the electrical current. When it comes to smaller screen sizes, projected capacitive touch screens are often chosen over capacitive touch screens. PCAP touch technology has drawn significant attention in mobile devices like the iphone and ipad. Its high precision multi touch functionality and high response speed makes it perfect for these kind of devices. Whitepaper The Projected Capacitive Touch Screen Handbook 5

7 PCAP touch technology also took care of the disadvantages of capacitive touch. Next to a bare finger, they also work when operated by a hand covered in surgical gloves or other thin gloves. Another great advantage of projected capacitive touch screens is that they offer multi touch. Types of Projected Capacitive Touch Screens Projected capacitive touch screens come in both self-capacitive and mutual capacitive versions. Selfcapacitive PCAP sensors can only solve one touch at a time. Mutual capacitive PCAP sensors can resolve multiple touches at the same time. This is called multi-touch. Learn more touch screen technology terminology with our Free Touch Screen Glossary. Whitepaper The Projected Capacitive Touch Screen Handbook 6

8 Self-capacitive touch screens, or single touch screens, have the same X and Y grid as multi touch screens. The difference is that the columns and rows operate independently. Self-capacitive controllers do not measure each intersection, they only measure each row and column. That is why this type of touch screen can only resolve one touch point at the time. It can also result in ghost touches or misplaced location sensing. A self-capacitive touch screen creates a pair of 'ghost points' when the screen is touched with two fingers that are diagonally separated. The controller only knows that two columns and two rows have been touched. But it can't tell which coordinate pairs belong together, because it only scans individual electrodes, not electrode intersections. Whitepaper The Projected Capacitive Touch Screen Handbook 7

9 A multi touch screen consists of a grid of rows and columns (X and Y). Each intersection of the grid forms a capacitor. For example, a 16 by 14 grid would have 224 capacitors. A capacitor can temporarily store electrical energy and steal little bits of energy from neighbouring capacitors. A controller checks each conductor individually. This is what makes it possible to detect multiple simultaneous touch locations. A mutual capacitive touch screen controller scans every electrode intersection. That is why every intersection can be identified as a touch point. To sum up, a multi touch controller measures every intersection separately. A single touch controller measures each row and column, i.e. each individual electrode. Whitepaper The Projected Capacitive Touch Screen Handbook 8

10 Advantages of pcap PCAP touch technology is not just an Apple-trendy technology. It also holds some of the best characteristics of competing touch technologies. We have already named and praised the best quality of projected capacitive touch screens. The ability to detect multiple touch points at the same time. The amount of touches a PCAP touch screen can detect is unlimited. Multi touch opens up a whole new world of touch possibilities. Projected capacitive touch technology enables functionalities like pinch to zoom and gesture touch. Building automation companies and the security industry really benefit from multi touch and gesture touch. [ Further Reading Multi Touch Technology - How it Works ] Whitepaper The Projected Capacitive Touch Screen Handbook 9

11 Projected capacitive touch screens are known for their high durability and long life span. One of two materials is the base of PCAP touch screens. They can be made entirely of plain glass. This allows them to be immune for most chemicals and to operate in extreme temperatures. Glass made PCAP touch screens can also be sealed to meet the requirements for most wash-down and explosive environments. Another material to make a projected capacitive touch screen of is plastic. Using plastic makes the touch screen virtually unbreakable and have the flexibility to be contoured or bent. In general, projected capacitive touch screens are more durable than capacitive touch screens. They are more resistant to scratching and more resistant to surface contaminants and liquids. That is why you will find projected capacitive touch technology used mostly in harsh and rough environments. Because PCAP touch technology uses clear glass or plastic, it provides an excellent image quality. Unlike resistive touch screens it doesn't use any films or layers that will reduce transmissivity. Projected capacitive touch screens therefore offer excellent optical performance. Whitepaper The Projected Capacitive Touch Screen Handbook 10

12 Disadvantages of pcap Every upside has a downside. So next to the great advantages projected capacitive touch offers, there are a few disadvantages as well. PCAP touch screens must sense changes in capacitance as small as a few femtofarads. This makes them very sensitive to EMI (Electromagnetic Interference) and RFI (Radio Frequency Interference) from sources such as the power supply or LCD display. It also challenges the integration. Particularly when the touch screen is bonded to an LCD. By following the guidelines of the manufacturer, you can simplify integration and avoid typical issues like EMI. Projected capacitive touch screens rely on human-body capacitance to recognize a touch. So they currently do require a human as the touch object. Developments over the last few years have however added the option of the finger being gloved. Thin cotton gloves and thin surgical gloves around a hand are now acceptable touch objects for PCAP touch screens. This opens up possibilities for other industries. Just think about doctors wearing thin gloves around hospitals. Whitepaper The Projected Capacitive Touch Screen Handbook 11

13 Cover Lenses Different cover lenses and polarizers can be added on top of the projected capacitive touch screen. They help make the touch screen a better fit for the environment it will be installed in. If the application needs extra protection because it will be used in a harsh environment, thermally hardened glass is the best choice. Think about outdoor kiosk applications that need to endure all kinds of weather conditions and users. A thermally hardened cover glass will vandal-proof the touch screen application. Next to that special polarizers can be added to enhance the user experience of the touch screen operator. Add a polarizer that make the screen anti reflective, anti glare, anti-fingerprint or antismudge for better visibility. These kind of polarizers are great for projected capacitive touch screens used in direct sunlight or heavy store lighting. Whitepaper The Projected Capacitive Touch Screen Handbook 12

14 Typical PCAP Applications Whitepaper The Projected Capacitive Touch Screen Handbook 13

15 This Handbook was made by SKY-Technology B.V. De Trompet DC Heemskerk Phone: Whitepaper The Projected Capacitive Touch Screen Handbook 14