IOT: Java + Raspberry Pi + Pi4j+ PIR Motion Sensor +LED

Objective: The Objective of this exercise is to make the LED glow when the PIR Motion Sensor configured on Raspberry Pi detects any movement (or intruder) and displays a message in the console saying “Intruder Detected!”. If no movement is detected, it will print “All is quiet...”

YouTube Video:

The YouTube Video for this tutorial is available at this link.

GitHub Source:

https://github.com/agilerules/IOT/tree/master/iot-pi4j-sensors

Overview about PIR Motion Sensor:

PIR stands for Passive InfraRed. This motion sensor consists of a fresnel lens, a infrared detector and supporting detection circuitry. The lens on the sensor focuses any infrared radiation/wavelengths present around it towards the infrared detector. Our bodies generate infrared heat and as a result this gets picked up by the motion sensor. The sensor outputs a 5V signal for a period of one minute as soon as it detects us. It offers a tentative range of detection of about 6-7 m and is highly sensitive. When the PIR motion sensor detects a person, it outputs a 5V signal to the raspberry pi through its GPIO. And we define what the raspberry pi should do as it detects an intruder through Java Pi4J coding. Here we are just printing: “Intruder detected”.

The PIR Motion Sensor has 3 pins (as shown in the below diagram):

Pin 1: is a +DC Voltage, usually connected to pin 2 of Raspberry Pi.

Pin 2: is an output pin

Pin 3 is the pin connected to Ground

In certain PIR motion sensors you can even adjust the delay at which the sensor outputs a HIGH signal at the expense of compromising the accuracy. You just need to turn the two knobs on the sensor counter clockwise using a screwdriver.

Dependencies:

Software:

• Pi4j
• Java
• Maven (Please find my blog here on how to install Maven on Raspberry Pi)

Hardware:

• Raspberry Pi (installed with Java, Maven)
• 3 Jumper wires
• LED
• 220 Ohm Resistor
• PIR Motion Sensor
• Breadboard
• GPIO Ribbon Cable

Steps:

1.  Complete the following Wiring process of Raspberry Pi, LED, Resistor, PIR Motion Sensor and with few jumper wires as shown in the below diagram.

Wiring Diagram:

Breadboard Diagram:

1. A wire from Pin 6 to Ground ( - on Breadboard)
2. A wire from Pin 12 (GPIO_1) to + line on Breadboard
3. Fix the LED and the long end of LED Anode (+) to be connected to Resistor (Yellow side on top of Resistor)
4. Other end of Resistor (i.e the red colour on top) to the + line of Breadboard
5. LED Cathode (-) to – line of Breadboard
6. PIR Motion Sensor Power pin to Pin 2 (+5V Vc Power)
7. PIR Motion Sensor Middle pin to Pin 16 (GPIO 4)
8. PIR Motion Sensor GND (Ground) Pin to – line of Breadboard

2.  Now connect to Raspberry Pi using Putty with your Raspberry Pi Credentials and by-default, you will in the path /home/pi.

3.  For proper organization purpose, I created folders (using mkdir command) \projects. But this is not mandatory. You can even skip this step and move to next step.

mkdir projects

4. From the \projects folder, execute the following command to Git clone the code to your local raspberry Pi.

git clone https://github.com/agilerules/IOT.git

5.  Once the git clone is complete, you will see IOT folder created in \projects folder. Now go to IOT folder (using the command cd IOT) and you will see the folder iot-pi4j-sensors inside this folder IOT.

6.  Move to this iot-pi4j-sensors folder (using the command cd iot-pi4j-sensors)

7.  Now execute the following command to start the maven build and run the Java class PirMotionDetection.java in standalone mode. Incase if mvn command is not recognized then it means that maven is not installed on your Raspberry Pi.  Please follow my blog on how to install Maven on Raspberry Pi.

8. Now run the PirMotionDetection main class in standalone way using the following Maven command:

mvn exec:java -Dexec.mainClass="com.agilerrules.pi4j.sensors.PirMotionDetection" -Dexec.classpathScope=runtime

9. If there is any movement before the sensor, you will see the message “Intruder Detected!” and if there is no movement then you will see the message “All is quiet...”
10. Incase if you need to terminate the program, press Ctrl+C.

11. Here is the source code explanation below:

The complete project structure is available here:

a) Pom.xml:

The below is the library dependency that we need for this application:

pi4j-core – This is for Pi4J to communicate with Raspberry Pi GPIO pins.

<dependencies>

            <dependency>

                  <groupId>com.pi4j</groupId>

                  <artifactId>pi4j-core</artifactId>

                  <version>1.1-SNAPSHOT</version>

            </dependency>

   </dependencies>

Note: At the time of wiring this program, the Pi4j 1.1 is available as a SNAPSHOT version and is not available in Maven repository yet. So had to use the OSS Sonatype Repository URL.

<repository>

            <id>oss-snapshots-repo</id>

            <name>Sonatype OSS Maven Repository</name>

            <url>https://oss.sonatype.org/content/groups/public</url>

            <snapshots>

                  <enabled>true</enabled>

                  <updatePolicy>always</updatePolicy>

            </snapshots>

</repository>

b)  PirMotionDetection.java:

1.    Pi4j programs can be run with sudo user only. But with version 1.1, it is no more required if the program is enabled to run with Non Privileged Access using the following command. 

//This is required to enable Non Privileged Access to avoid applying sudo to run Pi4j programs

GpioUtil.enableNonPrivilegedAccess();

2.  Create gpio controller for PIR Motion Sensor listening on the pin GPIO_04 using the following Pi4j Libraries.

final GpioController gpioPIRMotionSensor = GpioFactory.getInstance();

final GpioPinDigitalInput pirMotionsensor =      gpioPIRMotionSensor.provisionDigitalInputPin(RaspiPin.GPIO_04, PinPullResistance.PULL_DOWN);

3.   Now create gpio controller for LED listening on the pin GPIO_01 with default PinState as LOW.

//Create gpio controller for LED listening on the pin GPIO_01 with default PinState as LOW                   

         final GpioController gpioLED = GpioFactory.getInstance();          

final GpioPinDigitalOutput led = gpioLED.provisionDigitalOutputPin(RaspiPin.GPIO_01,"LED",PinState.LOW);

led.low();

4.  Now create and register gpio pin listener on PIRMotion Sensor GPIO Input instance to listen for pin state changes and perform the following action:

     a) If the event state of PIR Motion Sensor is high then print the message “Intruder         Detected” and turn the LED ON by invoking the high() method.

      b) If the event state is Low then print "All is quiet.." and make the LED OFF by invoking the low() method.

//Create and register gpio pin listener on PIRMotion Sensor GPIO Input instance           

pirMotionsensor.addListener(new GpioPinListenerDigital() {

              

public void handleGpioPinDigitalStateChangeEvent(GpioPinDigitalStateChangeEvent event) {

//if the event state is High then print "Intruder Detected" and turn the LED ON by invoking the high() method

                        if(event.getState().isHigh()){ 

                        System.out.println("Intruder Detected!");

                        led.high();

                    }  

//if the event state is Low then print "All is quiet.." and make the LED OFF by invoking the low() method

                    if(event.getState().isLow()){  

                        System.out.println("All is quiet...");

                        led.low();

                    }

                  }

        });

5.   Now loop the program until the user aborts with CTRL+C

   try {          

                // keep program running until user aborts

                for (;;) {     

                    //Thread.sleep(500); 

                }      

            }          

            catch (final Exception e) {        

                System.out.println(e.getMessage());    

            }

6.   That’s the end of the tutorial. Hope it was useful.