Capacitive screen introduction

Mobile phone crystal 3.2*2.5mm 3225 26M (26.000MHZ) 7.5PF 10PPM 20PPM 30PPM

Single chip microcomputer STM32L151CCU6

Photocoupler

I. Overview The capacitive touch screen is a four-layer glass panel designed for high performance and durability. The inner surface and the interlayer are coated with a transparent conductive material called ITO. The outermost layer is a thin, scratch-resistant bauxite glass coating that is only 0.0015mm thick. This interlayer serves as the active working surface, while the four corners of the screen are connected to electrodes that help detect touch input. The inner ITO layer also acts as a protective screen, ensuring stable operation in various environments. II. Working Principle When a user touches the screen, their finger creates a coupling capacitor with the ITO-coated surface due to the body's electric field. A high-frequency signal is applied to the working surface, and when touched, a small current flows through the user’s finger. This current is then distributed among the four corner electrodes. The controller calculates the exact position based on the ratio of the currents from each electrode, allowing for precise and fast touch detection. III. Key Features - **Material**: Made of highly scratch-resistant glass (with a hardness rating of 7H), it resists damage from sharp objects and is unaffected by common environmental factors like water, dust, static, or oil. It also offers eye protection benefits similar to those of sunglasses. - **Sensitivity**: Detects even light touches with less than 2 ounces of pressure, responding in under 3 milliseconds. - **Accuracy**: Achieves up to 99% precision in touch recognition. - **Sharpness**: Available in three surface finishes: polished, etched, and industrial. - **Durability**: The SMT controller has an MTBF (Mean Time Between Failures) of over 572,600 hours, meeting military-grade standards. - **Touch Life**: Can withstand more than 50 million touches without any drift or loss of accuracy, requiring only one calibration. IV. Application Areas Capacitive touch screens are widely used in various industries: - **Financial Sector**: ATMs, bank teller machines, and automated cash machines. - **Retail & Catering**: Vending machines, ordering systems, ticket kiosks, and onboard navigation systems. - **Medical**: Ideal for laboratories, clean rooms, and medical record systems, as they are resistant to contamination from blood and chemicals. - **Public Services**: Used in housekeeping systems, public information kiosks, and navigation systems. - **Industrial Automation**: Perfect for factory control systems where anti-glare and resistance to strong light interference are essential. - **Entertainment**: Found in gaming machines like bingo, slot, and poker machines, offering reliable performance even under harsh conditions. - **Mobile Devices**: Adopted by major brands such as Apple (iPhone), Motorola (Milestone), Samsung (i8910 HD), Meizu (M8), Lenovo (O1), Nokia (X-6), Sony Ericsson (X10), and HTC (Hero). These screens provide a seamless and responsive user experience, making them a top choice across multiple applications.