Four wire resistive touch screen is a common touch screen technology, which works based on resistive voltage division and contact point positioning. The following is a detailed explanation of its working principle:
1. Basic structure
The four wire resistive touch screen consists of the following core components:
Two layers of conductive film:
Upper layer (touch layer): usually a flexible transparent conductive film (ITO, indium tin oxide) with a flat surface.
Lower layer (base layer): Fixed hard transparent substrate (such as glass), also covered with ITO conductive layer.
Spacer Dots: Distributed between two layers, ensuring that the two layers do not touch when not touched.
Electrode: Each layer has two electrodes arranged along the X-axis and Y-axis directions:
Upper layer: X+and X-electrodes (left and right sides).
Lower layer: Y+and Y-electrodes (upper and lower sides).
2. Working principle
The four wire resistive screen determines the coordinates (X and Y) of the touch point through voltage division measurement method, which is completed in two steps:
(1) Measure X coordinate
Applying voltage: Apply a constant voltage (such as 5V) between the X+and X-electrodes in the upper layer (X-axis direction) to form a horizontal voltage gradient.
Contact conduction: When touched, the upper film is compressed and deformed, making contact and conduction with the lower layer.
Reading voltage: Measure the voltage value at the contact point through the Y+or Y-electrode in the lower layer (Y-axis direction). The voltage value is proportional to the X coordinate of the touch point, thereby determining the X position.
(2) Measure Y coordinate
Switching voltage: Apply a constant voltage between the Y+and Y - electrodes in the lower layer (Y-axis direction) to form a vertical voltage gradient.
Contact conduction: Maintain touch pressure while the two layers continue to make contact.
Reading voltage: Measure the voltage value of the contact point through the X+or X-electrode in the upper layer (X-axis direction) to determine the Y-axis.
3. Key features
Time division measurement: The X and Y coordinates need to be measured in two steps and cannot be obtained simultaneously.
Single touch: Only supports single touch.
No need for a dedicated stylus: can be operated with fingers, stylus, or other hard objects.
Strong anti-interference ability: insensitive to environmental factors such as water stains and dust.
4. Advantages and disadvantages
advantage:
Simple structure and low cost.
Low power consumption, no need for complex circuits.
The transmittance is relatively high (about 80%).
Disadvantages:
Poor durability: Frequent touch may cause wear on the upper film.
The transmittance is lower than that of a capacitive screen.
Does not support multi touch.
