Being a software Engineer, I was not able to use what I have developed as an end user. Now, Internet of Things course providing an opportunity to implement an idea which we want to have with us and use the product for our-self as an end user. So I would like to choose Home Automation domain. Home Automation:
In home automation, all electronic devices are connected to a central system that automates all connected components based on user input. For example: lights turn on the way you walk, clap to turn on television, give a voice command to open windows etc. At present, we can see more useful and smart home automation kits are available in the market.
I want to investigate on few more useful thoughts that are coming under home automation, such as;
Email sending - somebody is home (with image): There are some situations we want to know when someone comes to visit us and we are not home. At that time, send an email attaching an image file with a subject as 'Alert: home visit'.
Turn on/off lights: Naturally we feel lazy sometimes (especially on weekends) and do not want to get up and turn on lights. We can implement a solution to turn on lights remotely.
Alarm system - when dustbin fills: In busy life we forget small things easily, one of them is dumping wastage. To get rid of this we can implement a system that runs alarm when dustbin fills.
Tracking Oxygen/CO2 levels: To lead a healthy life, we need to monitor our in-take oxygen percentage, so we need to track the oxygen levels in our home.
The DHT11 is basic digital temperature and humidity sensor. Internally it uses thermistor and a capacitive humidity sensor to measure surrounding atmosphere. It generates a digital signal on the data pin of raspberry pi device. It is easy to use and we can read new data recordings once every 2 seconds.
Wiring up DHT11 sensor on Raspberry Pi:
This DHT11 sensor has 4-pins. We can connect to any GPIO (General Purpose Input and Output) port on Raspberry Pi device. Here we are connecting to GPIO4(Input/Output. Or provides a master clock output (GPCLK0) to external circuits) of raspberry pi from the 2nd pin wi of DHT11.
Following figure represents the general wiring diagram of DHT11 temperature and humidity sensor to Raspberry Pi IO.
Connect 1st pin of DHT to 3V (pin#1) of Raspberry Pi device.
Connect 2nd pin of DHT to GPIO#4 of RPi and parallelly connect 2nd pin to a 470 Ohms resistor (if it doesn't work use 10K Ohms resistor).
Other end of resistor should be connected to 3V (pin#1).
Finally, connect 4th in of DHT to any one of GND (Groud) on Raspberry Pi device.
Programming to use Temperature and Humidity Sensor in Python:
To start and use the DHT sensor on raspberry pi we need to handle it through GPIO pins which can be accessed using programming. Here we are using Python, and to use the DHT on Raspberry Pi, first we need to install required packages available in python and their dependencies.
Setting up DHT-Python Packages:
Open LXTerminal and login as super user: 'sudo su'.
Enter the following commands: git clone https://github.com/adafruit/Adafruit_Python_DHT.git
Go to google sheets and click on 'Share' to a client email which you have got from the JSON file.
You are all set with OAuth2 Credentials. Now, go to Adafruit_Python_DHT/examples folder and open google_spreadsheet.py, and make the following changes;
DHT_TYPE = Adafruit_DHT.DHT11
DHT_PIN = 4
GDOCS_OAUTH_JSON = 'DHTLogs-3736f2d30591.json'
GDOCS_SPREADSHEET_NAME = 'DHT Humidity Logs'
Finally, run this google_spreadsheet.py program. You will see the updates on your spreadsheet on google, as below.
SPI Interface
Serial Peripheral Interface(SPI) is a serial data protocol which is used by small electronic devices and micro-controllers to transfer and exchange information. In SPI, the term serial represents that each bit in binary number is sent one at a time, on the same wire. Example: If we consider number 251, in binary system it is 11111011. These SPI devices divided into two categories: one is masters and the other is slaves.
Master - the device that starts communication.
Slave - receives instructions from master and does what the master says.
In SPI devices, master can communicate with many slaves, but usually one at a time.
To connect with SPI devices we need to have four necessary pins on Raspberry Pi device.
MOSI (Master Output, Slave Input) - Master uses this pin (line) to send the information to slave.
MISO (Master Input, Slave Output) - Master uses this line to read the information from slave.
SCLK (Serial Clock) - Each bit is read on the edge of the clock signal.
SS (Slave Select) - We have two different pins on RPi- CE0 & CE1. Use one on these for each slave device is the circuit. By using this line, master indicates which slave device should respond to the given instructions.
Enabling SPI on the Raspberry Pi:
Generally, we can use any of the GPIO Input/Output pins for SPI, because it is only the matter of reading input, and bringing pins high and low. On the other hand, five of the Raspberry Pi's GPIO pins have specialized alternative features(uses) for communicating over SPI. By using these pins you can use built-in libraries and tools instead of writing as much code. Those SPI pins on the GPIO header are:
MOSI - pin#19
MISO - pin#21
SCLK - pin#23
CE0(SS) - pin#24
CE1(SS) - pin#26
In default mode, SPI functions of above pins are disabled in Raspbian(OS). To enable them we need to do the following steps:
Open LXTerminal and enter the command: 'sudo raspi-config'.
Select 'Adavanced Options', by moving down arrow key and press Enter.
Select 'SPI' and press Enter.
Select 'Yes' and press Enter to continue.
Now, select 'Finish' option and press Enter.
Type the following command: 'sudo nano /etc/modules'.
Now you will see a file editor. Go to end of the file and add the following line: 'spi-dev'.
Press Ctrl + O and press Enter.
Press Ctrl + X to exit from file editor.
To shutdown pi enter the following command: 'sudo shutdown -r now'.
When the Pi restarts, SPI modules load automatically.
Using SPI from Python3:
To access SPI using Python, we need to install built-in libraries of python3-dev and module for Python that enables SPI devices accessible. Do the following steps:
Open LXTerminal and type command: 'sudo apt-get install python3-dev'.
Enter command: 'git clone https://github.com/doceme/py-spidev'.
Enter: 'cd py-spidev'.
To install: 'sudo python3 setup.py install'.
Now, we are setup with all installations to use SPI devices and to access them through Python3.
Nokia 5110 LCD Python Library (SPI):
Nokia 5110 Display is an inexpensive graphical display that's easy to use with modern linux-based development board like Raspberry Pi. To enable it to use on RPi, we have built-in library called Adafruit Nokia LCD Python library (http://adafru.it/dvf). This library allows you to connect the Nokia LCD to a Raspberry Pi or Beaglebone Black and
display graphics using the Python programming language.
Wiring - Nokia 5110 LCD on Raspberry Pi:
To connect Nokia 5110 LCD to a Raspberry Pi is simple because these boars use the same power consumption 3.3V. There is no need to use a level converter chip.
In general, we need to connect the LCD's SCLK, DIN and CS pins to the board's SPI pins, and
the LCD's RST and D/C pins to two free digital I/O pins. With this setup we can use the fast
hardware SPI support built into our Raspberry Pi board. The library also supports
software SPI on any 5 digital I/O pins (SCLK, DIN, CS, RST, D/C).
To install the dependencies, follow the below steps:
Now, you should
see the files /dev/spidev0.0 and /dev/spidev0.1 are available.
Dispaying Temperature and Humidity on Nokia LCD:
By combining all the above learned concepts, I want to display the readings of DHT11 Temperature and Humidity Sensor on Nokia 5110 LCD.
Below video shows;
Temperature and Humidity updates on LCD screen.
If humidity is high - Red LED
If humidity is low - Yellow LED
Following python code enables me to display the readings on LCD as well as LED signalling to indicate high(red) and low(yellow) humidity in the surrounding air.
Before going to write a program to blinking an LED, first we need to write a program to test whether IO (Input/Output) connections are working properly or not.
First setup the basic connections to start Raspberry Pi. Before we plug-in the power supply, need to construct a circuit that able to access input/output ports. To construct such a circuit we need,
LED (Light Emitting Diode)
Breadboard
GPIO (General Purpose Input ans Output) Header Pin
270 Ohms resistor (In our case 330 Ohms resistor)
Python 3
LED (Light Emitting Diode): Has 2 legs, longer one called the "anode'- it receives power, other called the "cathode"- it is the output leg.
Steps to check the IO connection:
Connect 40-pin GPIO Ribbon Cable one end into Raspberry Pi-GPIO Header, and the other end into GPIO-Header placed on the BeadBoard.
Place anode(longer) leg of LED on the same row as 3.3 V wire(pin 1), and cathode leg of LED is not the same row.
Take one 330 Ohms resistor and place on end on the same row as cathode leg of LED, and other end on the same row as GROUND wire(pin 6).
Connect the Pi to its power plug and now you will see the LED turn on.
Now you will test the circuit works, when you place the LED under the Pi's control.
Shutdown the Pi and unplug the power supply.
Disconnect the 3.3 V wire from header pin 1 and then connect it to pin 3 (GPIO2).
Plug the power back into the Raspberry Pi, and allow the Raspbian to load.
Controlling GPIO2 from a Terminal Window:
Open Application Launcher, and select LXTerminal.
Enter super admin access command: 'sudo su' and press enter.
To export the GPIO plugins enter following command: 'echo 2 > /sys/class/gpio/export'
List the files: 'ls /sys/class/gpio/gpio2'.
To set GPIO2 as an output and turn it on, excute following two commands: 'echo out > /sys/class/gpio/gpio2/direction' and 'echo 1 > /sys/class/gpio/gpio2/value'.
To turn GPIO2 off: 'echo 0 > /sys/class/gpio/gpio2/value'.
It is always a best practice to unexport the pin so that it is no longer under the control of the file system entries: 'echo 2 > /sys/class/gpio/unexport'.
Controlling GPIO2 from Python 3:
Open a new file in python 3 and save it as experiment1.py in any accessible directory (preferably /home/pi/).
Write the following program to control the GPIO2:
import RPi.GPIO
import time
RPi.GPIO.setmode (RPi.GPIO.BCM)
RPi.GPIO.setup (2, RPi.GPIO.OUT)
while True:
RPi.GPIO.output (2, True)
time.sleep(0.15)
RPi.GPIO.output (2, False)
time.sleep(0.15)
Execute the program in LXTerminal by using following command: 'python experiment1.py'.
Now, you will observe that LED blinking on and off with 1 second as its time span in each state.
If you want to stop the program, press Ctrl + C.
Basic Input:
We can find out whether the voltage that is coming into a pin from your external circuit is high or whether it is low, by using GPIO input pins. In this basic input experiment we construct a circuit that will see how to detect when a switch is closed. For this we need,
Switch (either a two-terminal on/off switch or four-terminal tactile push button)
330 Ohms resistor
Raspberry Pi has pull-up and pull-down rsistors built-in to all of the GPIO pins. We can choose any one to use from software programs.
Steps to construct a circuit:
Connect one end of switch to the same line of the GPIO input pin(pin 3) wire and other end to the one side of 330 Ohms resistor.
Other side of the 330 Ohms resistor should connect to the GPIO output pin wire.
Reading a GPIO pin from Terminal Window:
Open LXTerminal and enter as super admin by using command: 'sudo su'.
Enter the following commands: 'echo 2 > /sys/class/gpio/export'
'echo in > /sys/class/gpio/gpio2/direction'
'echo 0 > /sys/class/gpio/gpio2/active_low'
'cat /sys/class/gpio/gpio2/value'
Now, press the switch and then enter.
Enter the following command to unexport: 'echo 2 > /sys/class/gpio/unexport'.
Reading a GPIO pin from Python 3:
Write the following python program and save it as experiment2.py,
To setup Raspberry Pi 2 - Kit using a Television, we need to have,
Raspberry Pi 2 (acts as a very small computer)
MicroSD(Secure Digital) card that comes with Pi already contains NOOBS OS.
Modern Television (which supports HDMI)
HDMI cable
Adapter with micro-USB (power)
USB Keyboard and mice
Steps to OS installation:
Connect Raspberry Pi to a modern television using HDMI cable, since HDMI offers a high quality video and audio signal.
Insert 8GB microSD card with NOOBS OS installed, at the microSD socket is attached to the underside of the board.
Plug USB keyboard and mice to the USB ports, also connect the power supply to the power socket(micro-USB cable).
Now, you will be able to see the window shows list of OS installation options. In the list, select Raspbian and click Install.
Installation starts and shows the progress rate in the window. After the completion of installation you will be taken into the Linux GUI environment.
It is always a best practice to insert microSD card before supplying power to the Raspberry Pi. At the same time should not remove SD card without turning off the device. Because, the memory card contains the OS and Pi may use it at any point of time. Removing the card while Pi is accessing it may corrupt data and in some cases may stop the memory card working at all.
We can change the Operating System or update it to the latest version at any time. And when the Raspbian is installed, it creates a new user called pi and the default password is raspberry. You can change the password at any time by using 'Change User Password'. You can remove the USB connections like keyboard, mice etc. when they are not in use. Since Raspberry Pi can only supply a limited power to USB devices, it is always best practice to do not connect devices consume over 100mA.
Internet connetion:
We can connect to internet in possible ways.
Using Wi-Fi dongle: Insert Wi-Fi dongle to the USB port. At the top right corner of your desktop you can see network monitor which shows the current status of your network connection. When you click on it it shows you the networks available in its range. Select the one to which you want to connect and provide authentication.
Using Ethernet cable: To make wired network connection between Pi and network router we use ethernet cable. Plug one end of the cable into Ethernet socket on the Raspberry Pi and plug the other end of the cable into network router.
Now, you will be able to access internet.
Remote Desktop Connection:
To connect and access Raspberry Pi device on personal computer or laptop, I have used xRDP ( Microsoft's Remote Desktop Protocol) by using IP address. Example: 10.0.0.196
Now a days, each object is able to connect with other object
to expose some useful means to our daily life. More than two objects can also
be connected over a network called cloud, are acts as remote controls which
simplifies the human work and reduces the complexity.
Internet of Things(IoT) is an environment which provides unique identifiers to the objects ( includes humans, animals etc.) and network to transfer data among the objects with no human-to-human or human-to-computer interaction. These communications are possible when the integration between wireless technologies, micro electromechanical systems and internet together.
A thing, in the Internet of Things, can be an automatic detector and controller of room temperature, smart phone/smart watch, sensor that identifies the tire low pressure of an automobile and gives alert, a small machine that identifies a dog and provides food, a car sensor which provides available place in a parking lot and so on. Thees are few things we usually see in our routine life and we are much familiar to.
It can also referred as the Internet of Everything. The Internet of Things are most closely associated with machine-to-machine communication. Here we are learning course about
what is IoT? How it is useful to learn? What can we do using IoT?
