Difference between revisions of "Arduino/C2/Analog-to-Digital-Conversion/English"

Learning objectives

• ADC i.e. Analog to Digital Conversion
• ADC pins in Arduino
• ADC Resolution
• DHT11 Temperature and Humidity sensor
• Serial Monitor and Serial Plotter

Pre-requisites

• Electronics and
• C or C++ programming language

System Requirement

• Arduino Uno board
• Ubuntu Linux 16.04 OS
• Arduino IDE

External Components Required

• DHT11 sensor
• Breadboard
• Jumper wires

Image DHT11_pin.jpg

Arduino ADC pins will convert these analog values to digital values.

Image ADC_Resolution.png

This means, it can detect (2 to the power of 10) i.e. 1024 discrete analog levels.

• Resolution is the smallest change that can be measured
• Arduino gives 5V output voltage, so 5V divided by 1024 levels gives 4.89mV.
• That means, Arduino Uno can be sensitive to a minimal change of 4.89mV.

Image DHT11_Interface.png

Point to the image as per narration

• Arduino Uno has 6 built-in ADC channels (A0 to A5).
• ADC channels read analog signal in the range of 0-5V.
• Pin 1 of the DHT11 sensor is connected to 5V pin of Arduino.
• Pin 2 of the DHT11 sensor is the Data pin.
• This Data pin of the sensor is connected to analog pin A0 of Arduino.
• Pin 3 of the DHT11 sensor is connected to the ground pin of the Arduino.

Image Setup_Connection.jpg

Open Arduino IDE.

Select Include Library and then click on Manage Libraries option.

In the top right corner, we can see a search tab.

Here, type DHT11 and press Enter.

Click on version drop down box

Click on install button

Scroll down to the bottom of the screen and select SimpleDHT by Winlin.

In the version drop down box, we can select the latest version of the library.

Click on Install button to install the library.

Click on the Close button at the right bottom of the window.

Click on the Sketch menu and select Include Library.

Newly downloaded library usually appear at the end.

So scroll down to the bottom of the list and select SimpleDHT.

#include <SimpleDHT.h>

SimpleDHT11 dht11(pinDHT11);

Here we have initialized the data pin of DHT11 sensor which is connected to A0.

This command creates a DHT object.

{

Serial.begin(9600);

delay(500);

Serial.println("DHT11 Humidity & Temperature Sensor\n\n");

delay(1000);

}

Serial.begin() function initiate the serial communication.

It sets the data rate in bits per second for serial data transmission.

9600 represents the baud rate.

delay(500) is the delay time for the sensor to boot.

Serial.print command prints the header as specified here.

{

byte temperature = 0;

byte humidity = 0;

dht11.read(pinDHT11, &temperature, &humidity, NULL);

Serial.print(" Temperature & Humidity : ");

Serial.print((int)temperature);

Serial.print(" *C ");

Serial.print((int)humidity);

Serial.println(" % H");

delay(2000);

}

We have created two variables temperature and humidity for DHT sensor output.

dht11.read, reads the data from the sensor.

It stores the result in microcontroller’s register.

These lines prints the temperature in degree Celsius and humidity in percentage.

delay(2000) updates the current humidity and temperature readings every 2 seconds.

This code is available in the Code files link of this tutorial.

You can download and use it.

A pop up window will appear to save the current program.

Save the program as DHT11.

Now click on upload button to upload the current program on Arduino.

Serial Monitor

For this, click on the Tools menu and select Serial monitor.

The serial monitor window opens.

Temperature and humidity of the current place is displayed as expected.

Close the window.

Comment the line Serial.print( “Temperature & Humidity :”); as shown.

This will not print the text Temperature and Humidity.

For plotting, we require only the values of temperature and humidity.

Click on the tools menu and select serial plotter.

The serial plotter window opens.

The blue line indicates the temperature which is around 28 to 30 °C.

The red line is the humidity reading which is near to 45%.

The readings will vary depending upon where the experiment is done.

Now cover the sensor with your hands and you will see the fluctuating readings.

Close the window.

Features of DHT11

• It is useful for humidity readings between 20%-80% with ∓5% RH i.e. (Relative Humidity)
• It is useful for temperature readings between 0-50 °C with ∓2 °C

Summary

• ADC i.e. Analog to Digital Conversion
• ADC pins in Arduino
• ADC Resolution
• DHT11 Temperature and Humidity sensor
• Serial Monitor and Serial Plotter

Assignment

1. Raise an alarm by glowing the built in LED pin 13 of the Arduino
2. Modify the above existing code.

   Hint: Use If-else statement.

Assignment

1. Add 1 or 2 °C to the temperature value that you get on the serial monitor.
2. To increase the temperature reading, cover the DHT11 sensor with your hands.
3. Refer to the Assignment link of this tutorial for the source code.

About Spoken Tutorial Project

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Acknowledgement

And this is Saurabh signing off.

Thanks for joining.