Touch Sensor Types and Applications
Touch Sensor
Introduction
A sensor that is capable enough of capturing and recording the physical touch made by the operator can be defined as a touch sensor. Further, it is also referred to as a touch detector.Other than touch, it can capture a certain extent of proximity without direct interaction or physical contact. The touch sensor used in applications will reduce the overall manufacturing cost. For example, in computers, the usage of touch sensors eliminates mechanical objects like mouse and keyboard. Even the final product looks appealing in terms of design and outlook.
What is a touch sensor?
A touch sensor is an electronic sensor used in detecting and recording physical touch. Also known as tactile sensors, it’s a small, simple, low-cost sensor made to replace old mechanical switches we seen in the past.Touch Sensor Working Principle
These sensors are sensitive to any pressure or force applied or touch. The principle of touch is similar to that of a switch. When the switch is closed, the current flows otherwise there is no chance of the current to flow. Similarly, when the touch sensor senses the touch or proximity is captured then it acts like a closed switch otherwise it acts as an open switch. These sensors are also known as ‘Tactile Sensors’.
Types of Touch Sensors
The touch sensors are classified into two types. They are- Capacitive Touch Sensor
- Resistive Touch Sensor
Capacitive Touch Sensor
These are one of the most popular types among touch sensors. As the name suggests, capacitive touch sensors resemble similar to a capacitor. The capacitance of this sensor can be expressed by the formula.
c=ε0 *εr*A/d
Where,
‘ε0’ = Free space permittivity
‘εr’ = Relative Permittivity or permittivity of dielectric constant
‘A’ = Area of the parallel plates
‘d’= Distance among the plates that are parallel to each other
Commonly associated with MicroChip at42qt1010, a Capacitive touch sensor measures touch based on electrical disturbance from a change in capacitance. It consists of an electrode film on top of the glass panel that’s conductively coated with a printed circuit pattern around the outer viewing area.
How capacitive touch sensor work:
The user applies touch on the glass panelThe printed circuit panel around the outer viewing area of the glass panel creates an electrical charge across the surface
It results in a decrease in capacitance and allows the system to determine the touchpoint
Multiple touchpoints can be detected as well, allowing for touch pinch and spread
Capacitive touch sensor applications:
Portable devices such as smartphones and tablets (iPhones, iPad, etc.)
Home applications such as touch lamps
Automotives
Industrial
Advantages of a capacitive touch sensor:
- Doesn’t require pressure to be applied since
- it’s built on the glass itself, hence making force insignificant to sensing requirements
- Support for multi-touch
- High responsiveness
Disadvantages of a capacitive touch sensor:
- Vulnerable to abrasion
- Reliability concerns when used in harsh environments
- Doesn’t work with gloves or stylus
Resistive touch sensor
Resistive touch sensor measures touch through responding to the pressure applied to their surface. It consists of two conductive layers and a non-conductive separator. Unlike the capacitive touch sensors, it’s not multi-touch compatible.
How resistive touch sensor work:
The user applies pressure against the surfaceThe outside conductive layer is then pressed against the inner layer, resulting in voltage changes
The voltage changes are then compared to the starting voltage, allowing for the point at which the touch took place to be calculated
Resistive touch sensor applications:
Musical instruments, touchpads, etc.Older music players, game consoles, etc.
Office equipment
Advantages of a resistive touch sensor:
- Cost-effective and durable to be used in harsh environments
- Able to be used with stylus and gloves
- Less complex
- Low power consumption
Disadvantages of a resistive touch sensor:
- The inability for multi-touch technology unlike the capacitive touch sensors
- Dependent on pressure, require more pressure to be applied for sensing to take place
What does the touch sensor do?
A touch sensor is designed to function as a switch when a conducting object touches it. Other than touch it can feel the proximity based on which its functionality depends.What does a touch sensor measure?
These sensors can operate user interfaces based on the senses. A touch exerts the pressure on the sensor and makes it acts as a closed switch. They just measure the amount of force or pressure applied to the sensor and make it operate.How many types of sensors are there?
There are sensors classified as analog and digital ones. Further, most frequently used sensors in electronic industries are Temperature sensors, Ultrasonic sensors, IR sensors, Level sensors, Gas sensors, Smoke sensors, and so on.How does touch sensor work?
Working principle
What is touch sensor used for?
Key ApplicationsAs mentioned in my introduction, a touch sensor is used for a wide array of applications, with those being:
Touch sensor in robotics; a touch sensor is commonly used in robots, enabling basic movement and the ability to detect touch in its surroundings (E.g. When the robot runs into something, the touch sensor can have it to stop moving)
Smartphones, automotive, industrial applications
Touch sensor faucet in kitchens; allowing for control of running water without having to physically turn the knob
Most other applications that require pressure/distance measurement
Features
• Multiple electrode configurations• Voltage operation range of 1.8 V–18 V
• Analog or digital (I2C) interface
• Minimal software integration
• Rotary wheel, linear sliders and touch
pad options
• Temperature ranges from -40ºC to +110ºC
• Various package options
Benefits
• Mechanical button and switch replacementon a wide variety of applications
• Provides more intuitive user interfaces
• Increases reliability without moving parts
• Allows greater design freedom
• Provides a more contemporary look
• Reduces overall system cost
Applications
• Gaming controllers• Home entertainment
• Home appliances
• Cellular handsets
• Portable media devices
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