and I am one of the cofounders

of the Arduino project.

And we are here for another video

about our Arduino starter kit.

Today we are going to look at

a new project

called "The Touch Sensor Lamp".

This is a simple circuit

where we are going to build

a sensor that is able to detect

when a human being is

touching the circuit.

You can see that if I touch this

wire, the LED turns on.

For this tutorial we are going to

introduce a new concept

from the Arduino platform:

external libraries.

This is a very powerful concept because

there are some things

in Arduino programming

that are very complex for beginners.

Like for example, in this

case, we are building a touch sensor.

The touch sensor uses a

fairly complex process

for the beginner.

And it would be quite complex for

beginners to write the code

completely by themselves.

so someone with a lot of

skills in Arduino programming

developed a library that

is able to perform

this sensing function.

On the arduino website

you are going to find all the

instructions you need

in order to install

a new library

into the Arduino development enviroment.

But let's have a look at this circuit.

Here we have an LED

connected to pin number 12

of the Arduino.

And then we have this strange circuit,

where we have a resistor

connected between pin number 2

and 4 of our Arduino.

And then there is a wire

connected to pin number 2.

If i touch the wire with my finger,

the led turns on.

So, this is due to the passive sensor

implemented by the library

that we are going to see

in a few seconds.

The capacitive sensor is able to

detect when a human being

is touching a metallic surface.

It's the same principle used by

the touch sensor

on the screen of every iPhone

or Android mobile phones

that you may have used.

We can also increase the sensitivity

of the sensor

by using an external metallic surface.

I am going to use

a piece of printed circuit board

that hasn't been etched yet.

So as you can see

it is a piece of fiberglass

with some copper on top.

so we are going connect this

to my circuit and see

what happens if I place

a bigger surface.

So we are going to help ourself

using this alligator clip.

I am going to

connect the alligator clip to the wire

and then to the copper surface.

so now when

my hand touches the surface

it turns on and off.

Actually what happens is that

only if you actually have to

touch

the surface, it starts to

sense my hand even

when the hand is just close.

Actually if we flip

the board around here we have

an insulating surface made of

fiberglass and still

if I place my full hand on it,

it can still detect my hand.

so the capacitive sensor

is very useful because I

can actually detect the touch

of a person even through

certain insulating materials.

Now let's have a look at the code.

here you can see

something new already at the

beginning of the code.

We are going to use this statement

called "include".

You have this # sign followed by

include and CapSense.h

So, this statement tells Arduino

to look for a library called

CapSense and include that

into our program.

As I said before

this is quite useful because

it is going to introduce

a piece of code,

which is quite complex

and is going to make

your life very simple.

and you can find online literally

hundreds of libraries

that encapsulate the functionality

of very complex sensors.

And provide you a very simple

way to use them.

So they are an incredibly powerful

part of the Arduino platform.

So

a little further down in the code

you can see that we are creating

an object of type CapSense

and this object is called capSensor.

And we are specifying that pin

4 and 2

are the two pins connected to

the resistor and pin number 2 is

actually the one that goes to

the sensor.

So, later on we create

another variable called threshold

that is set to the value 1000.

this value will need to be

determined experimentally while you

work on your code.

And finally we create a

constant called ledPin

that specifies that the LED

is connected to pin number 12.

In the setup()

you see there is nothing complex.

There is a Serial.begin()

that opens a communication channel

with the computer at 9600 bits per second,

followed by a pinMode(ledPin, OUTPUT)

that makes sure that the pin

connected to the led is set

as an output

so that we can turn in on and off.

If we look at the setup(),

we can see that there is an

interesting command here.

We are using the CapSense library

to read from the sensor

and the number 30

witin brackets - here -

is indicating that we want

to read 30 samples

from the sensor.

This makes sure that we filter

out any unwanted noise or

false reading.

The value read by the sensor

goes into this variable

called sensorValue.

Later on we print sensorValue

towards the computer

so we can visualise it

with a serial monitor.

After that

comes the moment when we have actually

to decide if the led has to

be on or off.

If sensorValue is more

than the threshold then we turn

on the LED. If sensorValue

is less, then the LED turns off.

Then we introduce a small

10ms delay

to make sure that we are not

reading too fast

And afterwards we just

go back to the beginning of the loop,

we'll read the sensor again

and we continue like this.

If we switch on the serial monitor,

we can actually see

a series of numbers

coming from the sensor.

You can see that when I

approach with my hand the PCB

that I connected to the sensor,

the numbers increase.

And when the number

is bigger than a certain value

that we set which is 1000

in this case.

When the value is more than 1000

the LED turns on.

So this sensor

can also be used as a

proximity sensor

if properly configured.

Ok so

we are at the end of the tutorial

I hope you enjoyed this project

and see you later alligator.