IoT_car

Introduction

This is a Radio-controlled car, which you can control it on your mobile phone

Features

1. A camera is set at the front of the car to stream the video on your phone, so you can see if there is any obstacle
2. A sensor can help you to stop automatically to avoid collision
3. You can control the speed of motors by slider on the web interface

Prepare

• Car kit
• DC motor*4
• Camera
• Battery box*2
• Battery*8
• HC-SR04 Sensor
• L298N motor driver
• Dupont Line
• Breadboard

Before Getting Start

The first thing to do is to install Flask on your Raspberry Pi. Go to Terminal and enter:

sudo apt-get install python3-flask

Create a new folder to start your project

mkdir webapp

Go to the file you created, and new two folders templates and statics These two folders must under the folder webapp

cd webapp
mkdir templates
mkdir statics

Build up your Car

Click this link to learn how to build the car kit https://www.youtube.com/watch?v=uW8YVcBjPGU

L298N motor driver

In order to control your motor, you need to use L298N One motor driver can help us to control our motor in two parts. It depends on the way you connect Dupont Lines. In this project, I devided four motors into left side and right side. It can make sure that this car can turn left or turn right

Note: Make sure that wheels on the same side turn in the same direction

Click this link for more detail https://www.youtube.com/watch?v=bNOlimnWZJE&list=PLc6fhBPeC6SBbZFcrHLlPXyR2svfxf1RZ&index=19&t=507s

Sensor

Be careful that raspberry pi can only afford input 3.5V. However, sensor returns 5V to raspberry pi, so make sure that you connect resistance on the breadboard to decrease the voltage.

The way to connect resistance

Define pins that are connected with sensor on the respberry pi

TRIG = 26
ECHO = 3
gpio.setup(TRIG, gpio.OUT)
gpio.setup(ECHO, gpio.IN)

We need to initiate the TRIG pin for ready to sensor

Before turn the signal True to False, stay for a millisecond

def distance():
    gpio.output(TRIG, True)
    time.sleep(0.00001)
    gpio.output(TRIG, False)

Calculate the time of distance with the formula

Distance = Time X 34300 / 2

Return the result in the end of the function

    start = time.time()
    stop = time.time()

    while gpio.input(ECHO) == 0:
        start = time.time()
    while gpio.input(ECHO) == 1:
        stop = time.time()

    timeElapsed = stop - start
    distance = (timeElapsed*34300)/2
    print(distance)
    return distance

Click this link for more detail https://tutorials-raspberrypi.com/raspberry-pi-ultrasonic-sensor-hc-sr04/

Video Streaming

testMotor2.py

def gen(camera):
    """Video streaming generator function."""
    while True:
        frame = camera.get_frame()
        yield (b'--frame\r\n'
               b'Content-Type: image/jpeg\r\n\r\n' + frame + b'\r\n')


@app.route('/video_feed')
def video_feed():
    """Video streaming route. Put this in the src attribute of an img tag."""
    return Response(gen(Camera()),
                    mimetype='multipart/x-mixed-replace; boundary=frame')

The above script streams your camera video on index.html page as below:

<img src="{{ url_for('video_feed') }}" width="50%" />

Click this link for more detail https://www.instructables.com/id/Video-Streaming-Web-Server/

Control wheels

Take an example of controlling the car go forward

index.html

When pressing the image button, it will send a request to testMotor2.py and do the method post

<td>
  <form action="/forward" method="post">
     <input type="image" class="img" src="../statics/img/forward.png" />
  </form>
</td>

testMotor2.py

@app.route('/forward', methods=['GET', 'POST'])

The command line above connects html and python and do the function forward

def forward():
    init()
    while(distance() > 25):
        gpio.output(N1, False)  
        gpio.output(N2, True)
        gpio.output(N3, True)
        gpio.output(N4, False)
        time.sleep(0.5)

    stop()  //call stop function
    autoBack(0.5) // go backward for 0.5 second
    return render_template('index.html')

reference link: https://blog.csdn.net/weixin_42534940/article/details/81415768#5.%20%E5%B0%8F%E8%BD%A6%E6%8E%A7%E5%88%B6%E7%A8%8B%E5%BA%8F%EF%BC%88%E6%96%87%E4%BB%B6%E5%90%8D%E4%B8%BA%EF%BC%9Acar_controler.py%EF%BC%89%EF%BC%9A

PWM

Set up the pin on your respberry pi

gpio.PWM ( pin, frequency )

Note: the higher frequency you give, the more smoothly they turn

N2 = 22
N3 = 23
gpio.setup(N2, gpio.OUT)
gpio.setup(N3, gpio.OUT)
pwm1 = gpio.PWM(N2, 100)
pwm2 = gpio.PWM(N3, 100)

Get the paremeter speed pass from the slider in index.html, and mulitply 10 to percentage

value = request.form['speed']
speed = int(value)*10  // the value of slider is 0~10

start(0) give pwm a initial speed
ChangeDutyCycle(speed) change the speed of wheels

pwm1.start(0)
pwm1.ChangeDutyCycle(speed)
pwm2.start(0)
pwm2.ChangeDutyCycle(speed)

index.html

<div class="rangeSlider">
      <form action="/controlSpeed" method="post">
        <input
          type="range"
          name="speed"
          min="1"
          max="10"
          class="mySlider"
          id="sliderRange"
        />
        <p>Value: <span id="demo"></span></p>
        <input type="submit" value="ok" />
      </form>
</div>

Final Product

Put all the function together and assemble your car, try to use tape to fixed those stuff together

Demo video

https://www.youtube.com/watch?v=6ecvRyQtbPc