How touch sensors work and their applications

The human body has five sensory elements that are used to interact with our surroundings. Machines also need some sensing elements to interact with their surroundings. To make this possible sensors were invented. The invention of the first artificial sensor thermostat dates back to 1883. In the 1940s infrared sensors were introduced. Today, we have sensors that can sense motion, light, humidity, temperature, smoke, etc. ...... Both types of sensors, analog and digital, are available today. Sensors have revolutionized the size and cost of various control systems. One such sensor that can detect touch is the touch sensor.

What is a touch sensor?

Touch sensors are electronic sensors that can detect touch. They are used as switches when they are touched. These sensors are used in lamps, touch screens of mobile devices, etc. ...... Touch sensors provide an intuitive user interface.

Touch sensors are simple in design, low in cost and can be mass produced. With the advancement of technology, these sensors are rapidly replacing mechanical switches. Depending on their function, there are two types of touch sensors - capacitive sensors and resistive sensors

Capacitive sensors work by measuring capacitance and are seen in portable devices. They are durable, robust, attractive and cost effective. Resistive sensors do not depend on any electrical characteristics for their operation. These sensors work by measuring the pressure applied to their surface.

How touch sensors work

Touch sensors work similarly to switches. When they are subjected to touch, pressure, or external force, they are activated and act as a closed switch. When pressure or contact is removed, they act as an open switch.

Capacitive touch sensors contain two parallel conductors with an insulator between them. These conductor plates act as capacitors with a capacitance value of C0.

When these conductor plates are in contact with our finger, our finger acts as a conductive object. As a result, the capacitance will increase indefinitely.

The capacitance measurement circuit continuously measures the capacitance of the sensor C0. When the circuit detects a change in capacitance, it generates a signal.

Resistive touch sensors calculate the pressure applied to a surface to sense touch. These sensors contain two layers of conductive film coated with indium tin oxide, a good electrical conductor, separated by a small distance.

A constant voltage is applied to the surface of the film. When pressure is applied to the top film, it touches the bottom film. This produces a voltage drop which is detected by the controller circuitry and generates a signal to detect the touch.

Applications

Capacitive sensors are readily available and very low cost. These sensors are widely used in cell phones, iPods, cars, small appliances, etc. ... These sensors are also used to measure pressure, distance, etc. ... One disadvantage of these sensors is that they can give false alarms.

Resistive touch sensors work only when enough pressure is applied. Therefore, these sensors are not useful for detecting small amounts of contact or pressure. These are used in applications where a lot of pressure is applied, such as musical instruments, keyboards, touch pads, etc.