As there are more resistive touch screen suppliers on the market which make resistive touchscreens more popular and prices are falling down, so that resistive technology is becoming more widely used. In order to choose the best touch screen technology, application designers must consider the application requirements. Resistive touch screen technology requires only a simple printed circuit board design, unlike capacitive and inductive touch screen technology, which requires electrode or coil etch on the printed circuit board. Because the touch screen is directly overlaid on the display, so that the printed circuit board space required for mechanical switches or capacitive touch key electrodes can be saved. Resistive touch screens are not recommended for use in harsh environments, such as mines or work sites that are often exploding or dusty. Little damage on resistive touch screens can affect touch accuracy and linearity.
1.The working principle of resistive touchscreen:
1. A resistive touch screen is a transparent glass panel with a surface covered with a touch-responsive film.
2. The resistive touch screen panel consists of two resistive layers (ITO) and separated by the dot in between.
3. The two thin film layers of the resistive touch screen form a resistor network that acts as a voltage divider for the touch position detection function.
4. The touch screen causes a voltage change on the voltage divider formed by the resistor network. This voltage is used to determine the contact position of the touch screen.
5. The touch screen controller (TSC) converts the captured analog voltage signal into a digital touch coordinate signal. A built-in analog-to-digital conversion channel acts as a voltmeter for measuring analog voltage.
6. After touching the screen, the touch controller functioning as a voltmeter first applies a voltage gradient VDD at the X+ point and a ground voltage GND at the X-point. Then, the analog voltage on the Y-axis resistance is detected, and the analog voltage is converted into a value, and the X-coordinate is calculated using an analog-to-digital converter. In this case, the Y-axis becomes a sensing line. Similarly, the Y coordinate can be measured by applying a voltage gradient at the Y+ and Y-points.
7. Some touch controllers also support touch pressure measurement, or Z-axis measurement. When measuring the Z-axis coordinates, a voltage gradient is applied to the Y+ axis and the X-axis.
2.The 3 types of resistive touchscreen.
According to the number of sensing lines on the touch screen, the resistive touch screen can be further divided into three categories: 4-wire resistive touchscreens, 5-wire resistive touchscreens and 8-wire resistive touchscreens . The strip electrodes of the 4-wire touch screen are mounted on two different resistive layers (X+, X- are on the same layer, Y+, Y-the other resistive layer). The 5-wire touch screen has only round electrodes (X+, X-, Y+, and Y-) on the bottom layer. The top layer is used to measure the voltage during the touch process and the voltage gradient is applied only to the bottom layer.
The 8-line touch screen works like a 4-wire touch screen. Just add a reference voltage line to each line, so the final number of buses reaches 8. The new four lines are used to provide reference voltages to the original four lines. The 8-wire touch screen uses the measurement principle of a proportional measurement analog-to-digital converter.
Because of its low cost and simple touch sensing algorithm, 4-wire touch screens are widely used in low-end consumer electronics. 5 wire and 8-wire touch screens are used primarily for expensive high-end medical equipment and important industrial controllers. Eagle Touch as an experienced touch screen manufacturer we provided both 4 wire resistive touchscreens and 5 wire resistive touchscreens.