Kunlun Tongtai touch screen - capacitive touch screen design difficulties and precautions

The most far-reaching technological change in touchscreen performance is the shift from resistive to capacitive touchscreen technology. According to iSuppli, a market research agency, nearly 25% of touchscreen mobile phones will be transferred from resistive to capacitive touchscreens by 2011. The various benefits brought by capacitive touch screen technology will drive the rapid growth of the market.

When a traditional resistive touch panel senses a finger or stylus, the top layer of flexible transparent material is pressed down and touches the conductive material layer below. Whereas, projected capacitive screens have no moving parts. In fact, projected capacitive sensing hardware consists of a top layer of glass, followed by components in the X and Y axes, and an indium tin oxide (ITO) insulation layer covering the glass substrate. Some sensor suppliers make a single-layer sensor with an X- and Y-axis sensor and a small bridge assembly in a single-layer ITO that creates a capacitance between the sensor and the finger when a finger or other conductive object is close to the screen. This capacitance is quite small relative to the system, but it can be measured using a variety of techniques.

One such technique is the use of TrueTouch components, which involves quickly changing the capacitance and utilizing a bleeder resistor to measure the discharge time. This all-glass touch surface gives the user a smooth and smooth touch. End-product manufacturers also prefer glass screens, as the glass material gives the end-product a sense of industrial design with beautiful lines and provides high-quality capacitive signals for measurement touches. Finally, it's important to not only consider the appearance of the touch panel, but also how it works. In order to design a touch screen product with excellent performance, the following parameters must be noted.

Accuracy: Accuracy can be defined as the maximum positioning error in a predefined touchscreen area, measured in the straight-line distance between the actual position of the finger and the measured position. When measuring accuracy, a simulated or mechanical finger is used. Place your finger in an exact position on the panel and compare your actual position with the measured position. Accuracy is very important, and users expect the system to accurately find the position of their fingers. One of the most criticized drawbacks of resistive touchscreens is their low accuracy, which diminishes over time. The precision of capacitive touchscreens has created many new applications, such as virtual keyboards and handwriting recognition without a stylus. Figure 1 shows a structurally incomplete touch panel that shows a wandering finger position, when in fact the finger is moving in a straight line.

Finger spacing: Finger spacing is defined as the shortest distance on the screen between the center points of the two fingers as the touchscreen controller measures the position of the two fingers. Finger spacing is measured (Figure 2) by placing two analog or mechanical fingers on a panel and gradually closing the two fingers closer together until the system detects that both fingers are one finger. Some touchscreen vendors refer to the distance between the edges and the center point. The 10 mm finger spacing of a 10 mm mechanical finger indicates that multiple fingers are touching the screen, or that the distance between the fingers is 10 mm, depending on the specification of the touch controller. Without good finger spacing, you can't design a multi-touch solution. Finger spacing is especially important for emulated keyboards, as finger spacing on the screen is usually very short when using emulated keyboards.

Response time: Response time is defined as the time between a finger touch event on the touchscreen and an interrupt signal generated by the touchscreen controller. The measurement method is to electronically touch an environment that simulates a finger touchscreen, or to move an analog finger over a panel. Response time is especially important because it directly affects how quickly a user can move their finger across the screen; pan or flick the action; Write on the screen with your finger or pen. Touch panels with slow response times may have short pauses and no movement detection.

Kunlun Tongtai touch screen - capacitive touch screen design difficulties and precautions

Kunlun Tongtai touch screen - capacitive touch screen design difficulties and precautions

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