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Arduino: analog output - Contenido educativo

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Subido el 10 de enero de 2021 por David G.

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Hello! In this exercise we are going to use the same circuit we used in the 00:00:00
previous exercise. You can see that we have the voltage divider connected the 00:00:05
same way we connected it the previous day. We are reading from 5 00:00:10
volts to 0 volts using the A0 analog connector and we have the LED connected 00:00:19
to the Arduino board, the usual way, but there is something different. Instead of 00:00:25
of connecting it to number 13, the LED is connected to number 11. Why number 11? You 00:00:29
can see that numbers 11, 10, 9, 6, 5 and 3 have a line in front of the number. It means 00:00:37
that they are different, these connectors are different. It means that they can provide 00:00:47
also, they can provide, I mean, digital values, the same way we have been doing during the 00:00:54
previous days, high and low digital values, but these six connectors, the one with the 00:01:00
line in front of the number, can also provide analog values. 00:01:05
It means that we can send one volts, two volts, three volts, one and a half, two and a half, 00:01:11
2.40, 3.60, 3.75, whatever. 00:01:18
And if this LED is connected to 11, for instance, 00:01:25
it means that we will be able to provide, I don't know, maybe 240, 320. 00:01:28
It means that we will be able to control the intensity of the LED. 00:01:35
We will be able to decide if the LED will shine brighter or less bright. 00:01:42
Okay? 00:01:47
So, let's have a look at the simulation, I will show the code later to you. 00:01:47
If we are reading 0 using the A0 connector, 11 doesn't send anything to the LED, it doesn't 00:01:54
change. 00:02:04
If we move a little bit higher, it means that we are reading a number higher than 0, as 00:02:05
you can see the LED is shining a little bit. 00:02:11
If we move it and we read a number even higher, the LED will shine brighter, and the higher 00:02:14
the number we read, the brighter it will shine, okay? 00:02:21
This is the brightest value. 00:02:26
We go back to 0, 5, 0, 5. 00:02:29
You can see the ranges, you can see the range of values we are reading and sending to the 00:02:33
LED. 00:02:39
Before we have a look at the code, we need to consider, we need to take into account that A0, although it reads analog values, the Arduino board will work using integer numbers. 00:02:43
You remember that the analog input reads numbers from 0 to 1023. 00:03:01
We studied it in the previous exercise. 00:03:06
It means that we are going to use 1024 values. 00:03:09
number 0 is related to 0 volts 00:03:12
number 1023 is related to 5 volts 00:03:15
and for instance if we have 5012 00:03:18
the one in the middle, we will be reading 00:03:21
or using, reading in this case 00:03:25
2.5 volts, the value in the middle, ok? 00:03:27
there is a proportional relationship between the number we use 00:03:30
and the voltage we are reading 00:03:33
when we use these numbers as 00:03:35
output values, we are going to use 00:03:39
a lower range of values. We are going to use a range of 256 values. We will use numbers 00:03:41
from 0 to 255. 0 will be related to 0 volts, 255 will be related to 5 volts, and the one 00:03:51
in the middle, for instance I think 128, will be related to 2.5. Do you understand the idea? 00:04:00
There is a proportional relationship between the integer number and the voltage. 00:04:07
But it's the same idea. 00:04:13
Although the range is four times shorter, it's the same idea. 00:04:14
So how can we program this circuit? 00:04:19
Really, really easy. 00:04:21
I want to show the code to you. 00:04:22
The first thing we need to do is creating a variable. 00:04:23
In this case, our variable is called input. 00:04:27
We read the analog input with this block, leer pasador analogico, 00:04:30
the one that is connected to a zero, 00:04:34
and we store it in the variable called input. 00:04:36
And then, what do we do? We divide this 00:04:40
variable by 4. Why? Because of the range we are going to send, 00:04:44
we are going to use as output, is 4 times shorter 00:04:48
than the range we are using to read 00:04:52
values. And we use this range to send this 00:04:56
value to 11. 11 is here. It sends the value to the LED 00:05:00
and the LED shines according to the value we are sending. 00:05:04
Zero, it doesn't shine. 00:05:08
Here in the middle, it shines just a little bit, 00:05:10
and if we move here, it shines a lot, okay? 00:05:14
So, this is the circuit. 00:05:17
This is the first thing you have to do, create the circuit. 00:05:19
But this is not the exercise. 00:05:22
This is just the first step. 00:05:23
Your exercise is going to be a little bit different. 00:05:25
Your exercise is here. 00:05:28
is the RGB, we are going to use a new component 00:05:30
that is called the RGB LED, this here 00:05:34
is an LED with 00:05:38
four pins, four connectors. One of them 00:05:44
is called the red connector, one of them is called the blue connector and one of them is called 00:05:48
the green connector. And this one is the cathode and is connected 00:05:52
to the ground through the protection resistor, the one 00:05:56
we usually use with a value of 220 ohms, ok? Don't forget it. 00:06:00
So, it means that this LED will combine three colors, ok? 00:06:06
So, we will read three different values using A0, A1 and A2, ok? 00:06:11
Can you see that we have three voltage dividers connected the way we connect them? 00:06:18
We will use three variables instead of having input. 00:06:25
We will have input 1, input 2 and input 3, for instance. 00:06:28
We will read three values the same way we read them before, and we will send three different 00:06:32
analog outputs the same way we have sent them before. 00:06:41
One for the red, one for the blue, and one for the green. 00:06:45
So let's have a look at the simulation. 00:06:48
You will understand it better with the simulation. 00:06:50
If I move this one, this is the red control. 00:06:53
It means that I'm sending 5 volts, now I'm sending 5 volts through the red wires. 00:06:56
If I connect, if I use the second one to the maximum value, now I'm sending 5 volts using 00:07:03
the blue wire and it will happen something similar with this one. 00:07:09
Now it means that I'm sending 5 volts through the green wire, ok? 00:07:15
So the important thing is that we can combine, for instance, green and blue, and what happens 00:07:20
if we combine green and blue, we have this one that is 00:07:25
a different color. What happens if we combine blue 00:07:28
and red? We have purple, okay? So the idea 00:07:33
is that every color can be 00:07:37
produced using a combination of red, green, and blue. And the way to 00:07:40
I'm not going to show the code to you, but it's really simple. It's something like repeating 00:07:45
three times the code of the previous exercise. Using a variable, reading 00:07:49
it reading a number from the connector, A0, A1, and A2, storing the number in the variable, 00:07:53
dividing the variable by 4, and sending it to the output we want, 11, 10, and 9, okay? 00:08:03
So if you understand the first exercise, and if you have the connections for this one, 00:08:09
the exercise is really, really simple. 00:08:14
This is the exercise, controlling the LED RGB using three voltage dividers, okay? 00:08:16
Good luck. 00:08:23
Autor/es:
David Gonzalez Arroyo
Subido por:
David G.
Licencia:
Reconocimiento - No comercial - Compartir igual
Visualizaciones:
335
Fecha:
10 de enero de 2021 - 18:27
Visibilidad:
Público
Centro:
IES MARIE CURIE Loeches
Duración:
08′ 25″
Relación de aspecto:
1.78:1
Resolución:
1920x1080 píxeles
Tamaño:
23.49 MBytes

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