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Capacitive touch sensor report - project 4

From Physical Programming

Capacitive Touch Sensor

1 How the device operates
2 What the device is typically used for
3 How it can be interfaced with the Arduino micro-controller
4 Capacitive Sensor Examples
5 Reference

How the device operates

Capacitive sensor is a technology sensing proximity position based on capacitive coupling.

Many methods can the capacitive sensors be produced. A simple one way to form an on-off output is by using two layers and a spacer in between. Through a voltage to conductive objects causes positive and negative charges to collect on each object.

This sensor can sense the human body and the metal, when they touch the sensor. In addition to this, the sensor directly touches the metal plane, separated by plastic, glass and other materials. In combination of arduino boards, the sensors can create very interesting and an interactive work. Touch switch pin definitions are (1) output (2) power supply (3) ground.

What the device is typically used for

It’s been used extensively in computer technology like mouse, monitor and screen, and also other electronic devices such as mobile phones, MP3 players, laptop and other applications. With capacitive alternatives, it can replace the mechanical buttons with gesture-based touch screens and multi-touch. One of the examples f capacitive touch sensor is the Apple iPod click wheel. They can also be used as localized proximity sensors, or turning non-conductive materials like glass into physical interfaces for all kinds of electronics projects.

It can be manufactured with various types of decent materials such as plastic, wood, ceramic or other insulating material even paper, which enable the sensor to be perfectly concealed. Those insulator acts as fairly good pressure sensor with a logarithmic response. Due to the wide range of materials can be used, capacitive sensor has been useful in many applications.

How it can be interfaced with the Arduino micro-controller

1. The physical setup includes a medium to high value (100K - 50M) resistor between the send pin and the receive pin. The receive pin is the sensor terminal. Firstly connect a 10M resistor between pins 8 and 9 on the Arduino Board.

2. Connect a small piece of alluminum or copper foil to a short wire and also connect it to pin 9. A wire connected to this pin with a piece of foil at the end makes a good sensor. For most applications, the sensor is covered by a piece of insulating material, so that users do not actually touch the metal foil.