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 screen is a four-layer glass structure, with the inner surface and interlayer coated with ITO. The outermost layer is a thin bauxite glass protective layer, just 0.0015mm thick. The interlayer ITO coating serves as the working surface, while the four corners are connected to electrodes. The inner ITO layer acts as the screen layer, ensuring a stable working environment. II. Working Principle When a user touches the screen, their finger forms a coupling capacitor with the ITO-coated surface due to the body's electric field. A high-frequency signal passes through the working surface, causing a small current to be drawn by the finger. This current flows through the four corner electrodes, and the controller calculates the position based on the ratio of the currents from each electrode. This enables precise touch detection in less than 3 milliseconds. III. Key Features - Material: Made of scratch-resistant glass with a hardness of 7H, resistant to scratches, wear, and common environmental factors like water, dust, and static. - Sensitivity: Detects touches with less than 2 ounces of pressure, offering ultra-fast response times. - Accuracy: Achieves 99% accuracy for reliable performance. - Surface Treatments: Available in three finishes – polished, etched, or industrial. - MTBF: SMT controller has an MTBF of over 572,600 hours (per MIL-HDBK-217F1). - Touch Life: Can withstand over 50 million touches without drift, requiring only one calibration. IV. Application Areas Capacitive screens are widely used in financial systems such as ATMs, bank teller machines, and cash machines. They also find applications in retail, catering, and public services like vending machines, ticketing kiosks, and on-board navigation systems. These screens are ideal for medical environments where contamination resistance is critical. In industrial settings, they provide anti-glare performance under strong light conditions. Additionally, they are commonly found in gaming devices like bingo machines, slot machines, and poker machines. Many smartphones, including the iPhone, Motorola Milestone, Samsung i8910 HD, Meizu M8, Lenovo O1, Nokia X-6, and Sony Ericsson X10, use capacitive screens for superior user experience.