Explain the operation of a resistive touch screen.
1 Answer
A resistive touch screen is a type of touch-sensitive input device commonly used in various electronic devices such as smartphones, tablets, and some industrial applications. It operates based on the principle of changes in electrical resistance when pressure is applied to the screen.
Here's a step-by-step explanation of how a resistive touch screen works:
Layer Construction: A resistive touch screen typically consists of two main layers: a flexible, transparent conductive layer on top (usually made of indium tin oxide - ITO) and a rigid layer beneath it. The top layer is called the "touch" or "pressure-sensitive" layer, while the bottom layer is called the "base" or "reference" layer.
Electrically Insulating Gap: There is a small air gap between the two layers when the screen is not being touched. This gap prevents direct electrical contact between the two layers.
Electrical Conductivity: Each of the two layers has a unique electrical conductivity property. The ITO-coated layer on the top is resistive, which means its electrical resistance changes when pressure is applied. The base layer, on the other hand, is conductive and maintains a constant electrical resistance.
Measurement Circuit: Around the edges of the touch screen, four electrodes are positioned, one on each side. These electrodes are connected to the resistive layer (top layer) at two points and to the conductive layer (base layer) at the other two points.
No Pressure (Idle State): In the idle state, when no pressure is applied to the screen, the resistive layer remains separated from the conductive layer by the insulating gap. As a result, there is no direct electrical contact between the two layers, and the touch screen registers no touch input.
Pressure Applied (Touching the Screen): When a user touches the screen, the flexible top layer gets deformed and comes into contact with the rigid base layer beneath it. The pressure on the top layer causes the two layers to make contact at the point of touch.
Electrical Resistance Change: The contact between the two layers creates a path for electric current flow. As the top resistive layer is deformable, it changes its shape, and this causes a change in its electrical resistance. The resistance at the point of contact decreases.
Coordinate Calculation: The touch screen controller, which is a part of the touch screen system, measures the electrical changes at the four edges of the screen. By analyzing these measurements, the controller can determine the position of the touch accurately. The controller uses algorithms to convert the electrical measurements into X and Y coordinates, representing the exact point of touch on the screen.
Data Transmission: The touch screen controller sends the calculated coordinates to the device's operating system, which translates the information into commands or actions, such as moving a cursor, tapping an icon, or zooming in/out.
Multi-Touch Support: Some resistive touch screens can support multi-touch gestures by sensing multiple points of touch simultaneously. However, they are generally less accurate and responsive compared to capacitive touch screens commonly used in modern devices.
Resistive touch screens have been widely used historically, but they are gradually being replaced by capacitive touch screens due to their superior performance and sensitivity. Nonetheless, resistive touch screens are still found in some specific applications that require resistance to dust, water, or the ability to work with gloved hands.
Here's a step-by-step explanation of how a resistive touch screen works:
Layer Construction: A resistive touch screen typically consists of two main layers: a flexible, transparent conductive layer on top (usually made of indium tin oxide - ITO) and a rigid layer beneath it. The top layer is called the "touch" or "pressure-sensitive" layer, while the bottom layer is called the "base" or "reference" layer.
Electrically Insulating Gap: There is a small air gap between the two layers when the screen is not being touched. This gap prevents direct electrical contact between the two layers.
Electrical Conductivity: Each of the two layers has a unique electrical conductivity property. The ITO-coated layer on the top is resistive, which means its electrical resistance changes when pressure is applied. The base layer, on the other hand, is conductive and maintains a constant electrical resistance.
Measurement Circuit: Around the edges of the touch screen, four electrodes are positioned, one on each side. These electrodes are connected to the resistive layer (top layer) at two points and to the conductive layer (base layer) at the other two points.
No Pressure (Idle State): In the idle state, when no pressure is applied to the screen, the resistive layer remains separated from the conductive layer by the insulating gap. As a result, there is no direct electrical contact between the two layers, and the touch screen registers no touch input.
Pressure Applied (Touching the Screen): When a user touches the screen, the flexible top layer gets deformed and comes into contact with the rigid base layer beneath it. The pressure on the top layer causes the two layers to make contact at the point of touch.
Electrical Resistance Change: The contact between the two layers creates a path for electric current flow. As the top resistive layer is deformable, it changes its shape, and this causes a change in its electrical resistance. The resistance at the point of contact decreases.
Coordinate Calculation: The touch screen controller, which is a part of the touch screen system, measures the electrical changes at the four edges of the screen. By analyzing these measurements, the controller can determine the position of the touch accurately. The controller uses algorithms to convert the electrical measurements into X and Y coordinates, representing the exact point of touch on the screen.
Data Transmission: The touch screen controller sends the calculated coordinates to the device's operating system, which translates the information into commands or actions, such as moving a cursor, tapping an icon, or zooming in/out.
Multi-Touch Support: Some resistive touch screens can support multi-touch gestures by sensing multiple points of touch simultaneously. However, they are generally less accurate and responsive compared to capacitive touch screens commonly used in modern devices.
Resistive touch screens have been widely used historically, but they are gradually being replaced by capacitive touch screens due to their superior performance and sensitivity. Nonetheless, resistive touch screens are still found in some specific applications that require resistance to dust, water, or the ability to work with gloved hands.