Fuel level measurement

                   

We used Ultrasonic Sensor HC-SR04 for the purpose of measuring the level of the Fuel

Hardware requirement

1. HC-SR04
2. 1k Ohm Resistor
3. 1.5k Ohm   Resistor
4. Jumper wires
5. BreadBoard

Specification of HC-SR04:

Power Supply :+5V DC
Quiescent Current : <2mA
Working Current: 15mA
Effectual Angle: <15°
Ranging Distance : 2cm – 400 cm/1? – 13ft
Resolution : 0.3 cm
Measuring Angle: 30 degree
Trigger Input Pulse wi

dth: 10uS
Dimension: 45mm x 20mm x 15mm

Pins :

1. VCC: +5VDC
2. Trig : Trigger (INPUT :Sends pulses to object)
3. Echo: Echo (OUTPUT :output is of 5v)
4. GND: GND

Voltage Divider:

The ECHO output is of 5v. The input pin of Raspberry Pi GPIO is rated at 3.3v. So 5v cannot be directly given to the unprotected 3.3v input pin. Therefore we use a voltage divider circuit using appropriate resistors(always R1=R and R2<=2R) to bring down the voltage to 3.3V.

Circuit Diagram:

Screenshot of the Hardware connections:

Output :

Python Code:

We used the Python script to interact with the Hardware as there is a limitation in Java while interacting with these kind of sensors(because of waiting issue).

import time

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM) #GPIO_mode=BCM=refers pin by broadcom SOC channel number

GPIO_TRIGGER=14 #assign TRIGGER output pin num=14

GPIO_ECHO=15#assign ECHO I/P pin num=15

GPIO.setup(GPIO_TRIGGER,GPIO.OUT)

GPIO.setup(GPIO_ECHO,GPIO.IN)

GPIO.output(GPIO_TRIGGER,False)

time.sleep(0.5) # waits for 0.5s

GPIO.output(GPIO_TRIGGER,True)

time.sleep(0.00001)

GPIO.output(GPIO_TRIGGER,False)

start = time.time()

while GPIO.input(GPIO_ECHO)==0:

 start = time.time()

while GPIO.input(GPIO_ECHO)==1:

 stop = time.time()

elapsed=stop-start

distance=elapsed*34000

distance=distance/2

print "Distance: %.1f"%distance

GPIO.cleanup()

Java Code:  

As we are publishing the sensor data to the cloud using Kura, We will use the Java code to execute and get output of the python script.

Also we used ScheduledExecutorService  to schedule the publishing for every 30 seconds interval

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
public class CallPython {
    static ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(1);
    public static void main(final String[] args) {
        try {
            scheduledExecutorService.schedule(new Runnable() {
                @Override
                public void run() {
                    final Runtime r = Runtime.getRuntime();
                    Process p = null;
                    try {
                        p = r.exec("sudo python DistanceMeasure.py");
                    } catch (final IOException e) {
                        e.printStackTrace();
                    }
                    final BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));
                    String line = "";
                    try {
                        while ((line = br.readLine()) != null) {
                            if (line.contains("Distance:")) {
                                System.out.println("Distance: " + line);
                            }
                        }
                    } catch (NumberFormatException | IOException e) {
                        e.printStackTrace();
                    }
                }
            },
            30,
            TimeUnit.SECONDS);
        } catch (final Exception e) {
            final String cause = e.getMessage();
            if (cause.equals("python: not found")) {
                System.out.println("No python interpreter found.");
            }
        }
    }
} .