Projected capacitive touch screen displays function using an electrostatic field created by conductive materials that are layered together forming a grid of electrodes. During use, touch the display with your finger or a conductive stylus causes an interference with the electric field above the display surface. This slight capacitance change is detected by the controller interpreting the X and Y coordinates. This technology allows for simultaneous multiple finger tracking and the controller is designed to support the common multi-touch patterns.
The basic science behind projected capacitive touch technology
There is a wide range of structures that make up projected capacitive technology. The one sheet piled up design has the X and Y electrodes combined on one sheet. The other single sheet two-sided structure has the X electrodes on its surface and Y electrodes on the backside of the sheet. The double-sheets-laminated component is made up of two sheets that are facing each other and the electrodes placed in between them. For the two-sheets-laminated make of the projected capacitive, on one glass we have the X electrodes forming while the Y electrodes form on the other glass. The lamination of the two glass sheets is done in such a way that the two electrode sides face each other while the X and Y electrodes intersect in a matrix manner. In projected capacitive technology there exist two forms of sensing methods. These two types of sensing include: wire sensing type and GRID sensing type. An introduction to the GRID type shall be discussed here. The human body is a good conductor because it has a high volume of water. If a finger is placed close to the model of the X and Y electrodes, there will be an occurrence of a capacitance coupling between the electrodes and the finger. This capacitance coupling results to a change in the electrostatic capacitance that is between the X and Y electrodes. A touch sensor has the ability to detect the touched points as it inspects where the electrostatic capacitance change occurred on the lines of the electrode.
The common features of projected capacitive touch panel solutions
The following are reasons why projected capacitive technology is of interest:
- Projected capacitive can support several touches, this makes it be in a position to support different complex inputs.
- The projected capacitive has no moving components thus has a longer life.
- Projected capacitive is more durable.
- The sensor’s sensitivity can be adjusted. When sensitivity is adjusted to a high level, it is easy to operate the touch screen over a cover plastic sheet or cover glass. The cover sheets enhance durability, flexibility of the model and also environmental resistance.
- It is possible to operate the projected capacitive with gloved fingers if sensitivity is increased.
- When it comes to optical property the projected capacitive touch screen is the best.
- Projected capacitive does not need any pressure force to detect for it easily senses light touches.
A more developed technology is required to measure the electrostatic capacitance and obtain accurate information on location from it. Different from the resistive touch screen display technology, it does not just work by connecting a touch screen with a controller from somewhere else. The controller and projected capacitive touch screen should both be made together. Because of its detection ability the projected capacitive is vulnerable to electrical noise. The sensor is highly influenced by LCD noise. In the recent times, a wide range of methods has established to reduce the vulnerability to noise.
The reason why projected capacitive technology has a high production cost
Projected capacitive is commonly applied in smartphones, although it has also been applied in other devices like touch screen PCs, portable audio players, touch screen monitors and mobile gaming devices. But one of the drawbacks is that it has a high production cost due to the need for fine patterning. Despite having not been discussed here, wire sensing type is more resistant to environmental factors like strong winds, rain and changes in temperature. It is possible to operate it by gloved hands or even bare hands. Due to these strong features wire sensing method is applied in digital signs and other terminals that could be exposed to harsh environment outdoors.
Three major advantages of projected capacitive touch sensors
- They are highly durable (serve long)
- Offer the best optical performance(excellent transmission ability)
- Multi-touch is not limited(depend on the controller)
Projected capacitive touch screens are at times completely made of plain glass; this makes them withstand chemicals and makes it possible to operate them in extremely high temperatures. They are also sealed to make them endure explosive environments. They could also be entirely made from plastic to reduce the chances of breaking and also enhance flexibility for easy bending. Projected capacitive touchscreens are able to sense the many fingers that can be placed on the screen.
Three significant disadvantages of projected capacitive technology
- Integration tends to be difficult due to noise sensitivity
- Can only sense finger touches (could change with time)
- They are relatively costly
Projected capacitive touch screens are designed to sense changes even as small as (10-15F), they tend to be highly sensitive to interference from electromagnetics. This poses a challenge to integration especially if the touch screen comes attached to an LCD; this makes the screen large by almost twenty two inches (diagonal) which is not easy to design. Projected capacitive touch screens depend on capacitance from the human body to generate a touch that can be detected; currently humans are the touch object. If you are looking for capacitive touch display solutions, then contact Faytech North America to speak with one of our display experts. We can help you determine the best solution for your specific industry needs and requirements.