Working principle of a touch sensor
The touch sensors are classified in two categories
Capacitive touch sensor
Resistive touch sensor
You can very easily spot the Touch Sensors in various applications in your daily life.
As per their functions the Touch Sensors are classified into two types which are used in different circumstances and utilities.
Since these sensors can be produced very easily in a very large scale can be made in very less cost and are very attractive in design. These are widely used in ipods, mobile phones, home appliances, automotive and many other industrial applications. They are used in applications such as measuring pressure, acceleration, distance etc.
Unlike the above these sensors can not sense the small contact or touch. Resistive Touch Sensor require an amount force to operate, so they are used in applications such as Foot pronation monitoring, musical instrument, keypads (mostly used in old mobile phones), resistive touch-pads and many other applications.
The resistive touch sensor consist of the two conductive layers which are separated by a very small distance or dots. The two layers (i.e the top as well as the bottom layer) are made up of a film. The films are generally coated by the Indium Tin Oxide which is a good conductor of electricity and is also transparent in nature as well.
A constant voltage is applied across the surface of two films. When the pressure is applied with the help of the finger or an stick on the top film, the sensor is activated and senses the touch.
The sensor operates when the enough pressure is applied, the top film touches the bottom film. When the two film touches each other they create the potential drop. The point of contact of the two film creates the voltage divider at that particular coordinate on the X-Y plane assumed at the film.
The change in the voltage hereby detected by a controller circuit and the location (coordinate) at which the voltage divider created is calculated.
The coordinate of the voltage divider in terns of X and Y axis created as the position of touch at which pressure is applied.