One of the two primary types of touchscreen displays (along with resistive) employed on smartphonestabletslaptops and similar electronic devices. The Apple iPhone is the most popular example of a capacitive touchscreen-based device.

Capacitive touch screens distinguish and sense specific touch location based on the electrical impulses in a human body, typically the fingertip. This enables capacitive touchscreens to not require any actual force to be applied to the screen’s surface; at the same time, capacitive screens typically don’t respond to styluses or gloved hands due to the lack of electrical impulses generated.

WORKING PRINCIPLE OF Capacitive Touch Sensor :

Capacitive Touch Sensor are also called as tactile sensors and are sensitive to touch, force or pressure. They are one of the simplest and using sensors. The working of a touch sensor is similar to that of a simple switch. When there is contact with the surface of the touch sensor, the circuit is closed inside the sensor and there is a flow of current. When the contact is released, the circuit is opened and no current flows.

The simplest form of a capacitor can be made with two conductors separated by an insulator. Metal plates can be considered as conductors. The formula of capacitance is shown below.

C = ε0 * εr * A / d

In capacitive touch sensors, the electrode represents one of the plates of the capacitor. The second plate is represented by two objects: one is the environment of the sensor electrode which forms parasitic capacitor C0 and the other is a conductive object like human finger which forms touch capacitor CT. The sensor electrode is connected to a measurement circuit and the capacitance is measured periodically. The output capacitance will increase if a conductive object touches or approaches the sensor electrode. The measurement circuit will detect the change in the capacitance and converts it into a trigger signal.In case of capacitive touch sensors, presence of a conductive material is enough to trigger the load and do not require any force. Hence, the risk of false or unintended triggers is higher in case of capacitive touch sensors.

USES OF THE Capacitive Touch Sensor

Capacitive touch sensors are widely used in most of the portable devices like mobile phones and MP3 players. Capacitive touch sensors can be found even in home appliances, automotive and industrial applications.


  • Operating Voltage: 2.0 – 5.5V
  • Operating Current(Vcc=3V):1.5 – 3.0μA
  • Operating Current(VDD=3V):3.5 – 7.0μA
  • Output Response Time: 60 – 220mS
  • Used Chipset: TTP223-BA6



Materials required:

  • Arduino
  • KY-019 Relay
  • TTP223B Capacitive touch sensor.
  • Jumper wires

Connection with Arduino: