# Introduction

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The following information is a single lesson in a larger project. Find more great projects here.

Project Overview:

In this project, you will create a light that turns on and off when you touch a strip of conductive material. The switch works based on capacitive sensing - your skin becomes part of the circuit!

## Step 1: Project Description

In this project you will create a lamp that turns on when you touch a strip of foil. We call this kind of interface a "touch sensor." The Arduino is measuring a change in capacitance when when your hand gets near the foil.
One cool thing about using capacitive touch sensors as buttons is that you can hide them under another material and they will still work. At the end of the project you will learn how to make an invisible button!

1. Capacitance is a measure of how much electrical charge an object can store.

2. The CapacitiveSensor library will be used to check two digital pins (4 and 2) which are called the send and sense pins. As the foil builds up electrical charge, the Arduino will measure how long it takes for pin 2 to have the same state as pin 4.

3. When your hand is close to the sensor, your skin will absorb some charge, making the characteristic charging time time longer!

4. Continue to the next step to learn how to build the circuit for the Touchy Feely Lamp.

## Step 2: Bill of Materials

Since this project relies on a conductive material to work and the CapacitiveSensor library to work, you won't be able to prototype the circuit in the simulator. You will need to use your Arduino kit to build the full project!

You will need the following electrical components:

1 LED

1 220 ohm resistor

1 M-ohm resistor ...and of course your Arduino Uno and a breadboard!

You will also need some wire and a strip of metal foil, like aluminum foil.

1. Can you match each component on the list to its location on the breadboard?

2. Continue to the next step.

## Step 3: Capacitive Sensing

Take a look at the circuit diagram for the project. There are not many components - the Arduino is doing most of the work using the library CapacitiveSensor.

Below are a few concepts to keep in mind as you work on the project.

1. Capacitance is a measure of how much electrical charge an object can store.
2. The CapacitiveSensor library will be used to check two digital pins (4 and 2) which are called the send and sense pins. As the foil builds up electrical charge, the Arduino will measure how long it takes for pin 2 to have the same state as pin 4.
3. When your hand is close to the sensor, your skin will absorb some charge, making the characteristic charging time time longer!
4. Continue to the next step to learn how to build the circuit for the Touchy Feely Lamp.

Next Lesson:Setting Up the Circuit

## Recommendations

• ### Arduino Class

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