Phones, cameras and tablets have touchscreens. How does it sense the touch? Which sensors are used, and how do these sensors work? What is the philosophy behind touch screens?
Does you ever think of it???
Broadly there are two type of Touch screen.
1)Resistive Touch Screens
2) Capacitive Touchscreens
Resistive Touch Screen:
A touch screen is a 2- dimensional sensing device that is constructed of 2 sheets of material separated slightly by spacers. A common construction is a sheet of glass providing a stable bottom layer and a sheet of Polyethylene (PET) as a flexible top layer.
The 2 sheets are coated with a resistive substance, usually a metal compound called Indium Tin Oxide (ITO). The ITO is thinly and uniformly sputtered onto both the glass and the PET layer. Tiny bumps called spacer dots are then added to the glass side, on top of the resistive ITO coating, to keep the PET film from sagging, causing an accidental or false touch. When the PET film is pressed down, the two resistive surfaces meet. The position of this meeting (a touch) can be read by a touch screen controller circuit.
Notice that some pins switch functions depending on if the controller is looking for a X-touch or a Y-touch position The controller reads the X and Y position many times per second so the user may move his stylus (or finger) rapidly across the touch screen and the data will be captured. This provides smooth operation and allows drag-and-drop or signature capture.
The Structure of Touchscreen Capacitive touchscreen is a four multi-layer glass. The two sides of the glass substrate are coated with uniform conductive ITO (indium tin oxide) coating. The thickness of 0.0015 millimeter silicon dioxide hard coating are coated on the front side of ITO coating layer. There are electrodes on the four corners for launching electric current.
Working PrincipleSmall amount of voltage is applied to the electrodes on the four corners . A human body is an electric conductor, so when you touch the screen with a finger, a slight amount of current is drawn, creating a voltage drop. The current respectively drifts to the electrodes on the four corners. Theoretically, the amount of current that drifts through the four electrodes should be proportional to the distance from the touch point to the four corners. The controller precisely calculates the proportion of the current passed through the four electrodes and figures out the X/Y coordinate of a touch point.
If you’ve found this useful, kindly share with others as it inspires and motivates us to come up with new ideas.
Ajaysai.Y
No comments:
Post a Comment