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Sep/12/2018

Projected Capacitive Touch

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Projected Capacitive Touch Introduction

Projected Capacitive Touch Technology (PCT or PCAP ) is fast becoming one of the most prevalent touch technologies for an expanding variety of applications ranging from consumer devices to commercial applications in retail, gaming and signage. Driven by the increasing number of users of touch-enabled mobile devices, consumer and professional expectations for touch applications have moved far beyond single touch requirements into the realm of multi-touch and multi-user capabilities. Projected capacitive touch offers many great advantages over the more traditional touch technologies. There is a reason why Apple chose PCAP touch technology for their iPhones.
 

How Projected Capacitive Technology Works

Projected capacitive technologies detect touch by measuring the capacitance at each addressable electrode. When a finger or a conductive stylus approaches an electrode, it disturbs the electromagnetic field and alters the capacitance. This change in capacitance can be measured by the electronics and then converted into X,Y locations that the system can use to detect touch.

273px-TouchScreen_projective_capacitive.svg
(Picture from https://commons.wikimedia.org/wiki/File:TouchScreen_projective_capacitive.svg)
 

Projected Capacitive Touch Screen Features

1.     Projected capacitive supports multiple touches, thus supports various elaborate inputs.
2.     Projected capacitive has relatively long life because it has no moving parts in operation.
3.     Projected capacitive has high durability.
4.     Sensitivity of the sensor can be adjusted. If sensitivity is adjusted to high level, the touch screen can be operated over a cover glass or cover plastic sheet. These cover sheets provide additional durability, environmental resistance, and a lot of flexibility in design.
5.     If sensitivity is increased, projected capacitive can be operated with gloved fingers.
6.     Projected capacitive touch screen is excellent at optical property.
7.     Projected capacitive responds to light touch. No pressure force is needed for detection.
8.     Projected capacitive requires an advanced technology to measure electrostatic capacitance and achieve precise locational information from it. Unlike resistive technology, it does not work simply by connecting a touch screen with a controller sourced from somewhere. A projected capacitive touch screen and controller need to be designed together.
9.     Projected capacitive is susceptible to electrical noise due to its detection mechanism. Noise from LCD is especially influential to the sensor. Recently, various methods are developed to improve tolerance for noise.
10.   Projected capacitive requires fine pattering, thus takes high processing cost.
11.   The notable application of projected capacitive is smartphone. Projected capacitive has also been dominant in personal devices such as portable PC, mobile game, and portable audio player.
12.   Strong at raining, wind, and temperature change. It can be operated either by bare hand or gloved hand. From these strong points, wire sensing technology is used for digital signage, and other outdoor terminals.