Resistive touch screens consist of a multi-layer composite film, with a layer of glass or acrylic as the base, coated with a transparent conductive layer, and topped with a smooth, scratch-resistant plastic layer that has been hardened. The inner surface is also coated with a conductive layer, and there are many tiny transparent spacer dots between the two conductive layers to keep them apart.
When a finger touches the screen, the normally insulated conductive layers make contact at the touch point. One of the conductive layers connects to a 5V uniform voltage field in the Y-axis direction, causing the voltage in the detection layer to change from zero to a non-zero value. The controller detects this connection, performs an analog-to-digital conversion, and compares the obtained voltage value with 5V to determine the Y-axis coordinate of the touch point, and similarly, the X-axis coordinate can be derived.
On the other hand, capacitive touch screens do not rely on finger pressure to change voltage values for coordinate detection. Capacitive screens work through any object that holds an electric charge, including human skin (the charge carried by the human body). Capacitive touch screens are made of materials such as alloy or indium tin oxide (ITO), with charges stored in a fine electrostatic grid that is thinner than a hair. When a finger touches the screen, it absorbs a small amount of current from the contact point, causing a voltage drop at the corner electrodes, thus achieving touch detection by sensing the weak current from the human body.
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