KS0470 Keyestudio 4WD BT Robot Car V2.0 Kit for Arduino

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About keyestudio

Keyestudio is a best-selling brand owned by KEYES Corporation, our product lines range from controller boards, shields and sensor modules to smart car and complete starter kits for Arduino, Raspberry Pi and BBC micro:bit, which designed for customers of any level to learn electronics and programming knowledge. All of our products comply with international quality standards and are greatly appreciated in a variety of different markets throughout the world.

You can obtain the details and the latest information through visiting the following web sites:http://www.keyestudio.com

References and After-sales Service

1.Download Profile：https://fs.keyestudio.com/KS0470

2.Feel free to contact us please, if there is missing part or you encounter some troubles. Welcome to send email to us：service@keyestudio.com. We will update projects and products continuously based on your sincere advice.

Warning

1.This product contains tiny parts(screws, copper pillars), keep it out of reach of children under 7 years old please.
2.This product contains conductive parts (control board and electronic module). Please operate according to the requirements of this tutorial. Improper operation may cause overheating and damage parts. Do not touch and immediately disconnect the circuit power.

Copyright

The keyestudio trademark and logo are the copyright of KEYES DIY ROBOT co.,LTD. All products under keyestudio brand can’t be copied, sold and resold without authorization by anyone or company. If you’re interested in our items, please contact to our sales representatives: fennie@keyestudio.com

Introduction

Nowadays, technological education such as VR, kids programming, and artificial intelligence, has become mainstream in educational industry. Thereby, people attach importance to STEAM education. Arduino is pretty notable in Maker education.

So what is Arduino? Arduino is an open-source electronics platform based on easy-to-use hardware and software. Arduino boards are able to read inputs - light on a sensor, a finger on a button, or a Twitter message - and turn it into an output - activating a motor, turning on an LED, publishing something online. Based on this, Keyestudio team has designed a 4wd robot. It has a processor which is programmable using the Arduino IDE, to mapped its pins to sensors and actuators by a shield that plug in the processor, it reads sensors and controls the actuators and decides how to operate.

15 learning projects, from simple to complex, will guide you how to make a smart 4wd robot on you own and introduce the detailed knowledge about sensors and modules.

Simultaneously, it is the best choice if you intend to obtain a DIY robot for learning programming, entertainment and competition requirement.

Features

1.Multi-purpose function: Obstacle avoidance, follow, IR remote control, Bluetooth control, ultrasonic follow and displayed face emoticons.
2. Simple assembly: No soldering circuit required, complete assembly easily.
3. High Tenacity: Aluminum alloy bracket, metal motors, high quality wheels and tracks
4. High extension: expand other sensors and modules through motor driver shield and sensor shield
5. Multiple controls: IR remote control, App control(IOS and Android system)
6.Basic programming：C language code of Arduino IDE.

Specification

Working voltage: 5v
Input voltage: 7-12V
Maximum output current: 2A
Maximum power dissipation: 25W (T=75℃)
Motor speed: 5V 200 rpm/min
Motor drive mode: dual H bridge drive
Ultrasonic induction angle: <15 degrees
Ultrasonic detection distance: 2cm-400cm
Infrared remote control distance: 10 meters (measured)
Bluetooth remote control distance: 50 meters (measured)
Bluetooth control: support Android and iOS system

Product List

Assembly Guide

Step 1:Mount the Bottom PCB Prepare the parts as follows:

Gear motor *4
Fixed part *4
M3 nickel plated nut *10
M3*6mm round-head screw *14
4WD bottom PCB *1
Tracking sensor *1
Wheel *4
Dual 5p wire *1
M3*40mm copper pillar*6
M3*30m round-head screw *8
M3*8mm round-head screw *2

Step 2: Install Dot Matrix

Prepare the parts as follows:

8*16 LED panel *1
4Wd baffle
4P wire *1
M2x8mm round-head screw *4
M2 nut *4

Step 3: Servo plastic platform

Prepare the parts as follows: Servo *1 M2*4 screw *1 Black cable tie*2 Ultrasonic sensor*1 Black servo platform *1 M1.2*4 tapping screw *4 M2*8 tapping screw *2

Step 4: Install the Top PCB

Prepare the parts as follows:

Top PCB *1
M3 nut *3
Motor drive board *1
Control board *1
IR receiver module *1
M3*10mm copper pillar *8
M3*8mm round-head screw *1
M3*6mm round-head screw *16
M3*10mm flat screw *2
6-Cell AA battery holder *1

Step 5: Install Top PCB

Prepare the parts as follows:

Bluetooth module *1
M3*6MM round-head screw *6
Jumper cap *8

Step 6: Hook-up Guide

6. Install Arduino IDE and Driver

Download software

When we get control board, we need to download Arduino IDE and driver firstly. You could download Arduino IDE from the official website: https://www.arduino.cc/, click the SOFTWARE on the browse bar, click “DOWNLOADS” to enter download page, as shown below:

There are various versions for Arduino, just download a suitable version for your system, we will take WINDOWS system as an example to show you how to download and install.

There are two versions for WINDOWS system, one is installed version, another one is download version, you just need to download file to computer directly and unzip it. These two versions can be used normally. Choose one and download on your computer.

You just need to click JUST DOWNLOAD, then click the downloaded file to install it. And when the ZIP file is downloaded, you can directly unzip and start it.

We need to know keyestudio V4.0 development board, as a core of this smart car.

keyestudio V4.0 development board is an Arduino uno-compatible board, which is based on ATmega328P MCU, and with a cp2102 Chip as a UART-to-USB converter.

It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz quartz crystal, a USB connection, a power jack, 2 ICSP headers and a reset button.

It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it via an external DC power jack (DC 7-12V) or via female headers Vin/ GND(DC 7-12V) to get started.

Installing driver

Let’s install the driver of keyestudio PLUS control board. The USB-TTL chip on PLUS board adopts CP2102 serial chip. The driver program of this chip is included in Arduino 1.8 version and above, which is convenient. Plug on USB port of board, the computer can recognize the hardware and automatically install the driver of CP2102.

If install unsuccessfully, or you intend to install manually, open the device manager of computer. Right click Computer----- Properties----- Device Manager.

There is a yellow exclamation mark on the page, which implies installing the driver of CP2102 unsuccessfully. Then we double click the hardware and update the driver.

Click “OK” to enter the following page, click “browse my computer for updated driver software”, find out the installed or downloaded ARDUINO software. As shown below:

There is a DRIVERS folder in Arduino software installed package（）, open driver folder and you can see the driver of CP210X series chips.

We click “Browse”, then find out the driver folder, or you could enter “driver” to search in rectangular box, then click “next”, the driver will be installed successfully. (I place Arduino software folder on the desktop, you could follow my way)

Open device manager, we will find the yellow exclamation mark disappear. The driver of CP2102 is installed successfully.

7. How to Add a Library?

（1）What are Libraries ?
Libraries are a collection of code that makes it easy for you to connect to a sensor,display, module, etc.
For example, the built-in LiquidCrystal library helps talk to LCD displays. There are hundreds of additional libraries available on the Internet for download.
The built-in libraries and some of these additional libraries are listed in the reference.
（2）How to Install a Library ?
Here we will introduce the most simple way for you to add libraries .
Step 1：After downloading well the Arduino IDE, you can right-click the icon of Arduino IDE.
Find the option "Open file location" shown as below:

Step 2: Enter it to find out libraries folder, this folder is the library file of Arduino.

Step 3：Next to find out the “libraries” folder of 4WD robot car(seen in the link: https://fs.keyestudio.com/KS0470)

You just need to replicate and paste IRremove and SR04 folders into the libraries folder of Arduino IDE.
Then the libraries of 4wd robot car are installed successfully, as shown below:

8. Projects

The whole project begins with basic program. Starting from simple to complex, the lessons will guide you to assemble robot car and absorb the knowledge of electronic and machinery step by step. I reckon that you could hardly sit still and itch to have a go, let’s get started.

Note: (G), marked on each sensor and module, implies negative pole, which is connected to “G”, ”-”or “GND”on the sensor shield and control board ; (V) represents positive pole, which is linked with V , VCC, + or 5V on the sensor shield and control board.

Project 1: LED Blink

(1)Description

For the starter and enthusiast, this is a fundamental program---LED Blink. LED, the abbreviation of light emitting diodes, consist of Ga, As, P, N chemical compound and so on. The LED can flash diverse color by altering the delay time in the test code. When in control, power on GND and VCC, the LED will be on if S end is high level; nevertheless, it will go off.

(2)Specification

Control interface: digital port
Working voltage: DC 3.3-5V
Pin spacing: 2.54mm
LED display color: red

(3) Equipment

(4) Wiring Diagram

The expansion board is stacked on development board, LED module is connected to G of shield, “+”is linked with 5V, S end is attached to D3.

(5)Test Code：

/*
 keyestudio 4wd BT Car V2
 lesson 1.1
 Blink
 http://www.keyestudio.com
*/
void setup()
 { 
    pinMode(3, OUTPUT);// initialize digital pin 3 as an output.
}
void loop() // the loop function runs over and over again forever
{  digitalWrite(3, HIGH); // turn the LED on (HIGH is the voltage level)
   delay(1000); // wait for a second
   digitalWrite(3, LOW); // turn the LED off by making the voltage LOW
   delay(1000); // wait for a second
}//*******************************************************************

(6)Test Result

Upload the program, LED flickers with the interval of 1s.

(7)Code Explanation

pinMode(3，OUTPUT) - This function can denote that the pin is INPUT or OUTPUT
digitalWrite(3，HIGH) - When pin is OUTPUT, we can set it to HIGH(output 5V) or LOW(output 0V)

(8) Extension Practice

We succeed to blink LED. Next, let’s observe what LED will change if we modify pins and delay time.

/*
 keyestudio 4wd BT Car V2
 lesson 1.2
 delay
 http://www.keyestudio.com
*/
void setup() {  // initialize digital pin 11 as an output.
   pinMode(3, OUTPUT);
}
// the loop function runs over and over again forever
void loop()
 { digitalWrite(3, HIGH); // turn the LED on (HIGH is the voltage level)
   delay(100); // wait for 0.1 second
   digitalWrite(3, LOW); // turn the LED off by making the voltage LOW
   delay(100); // wait for 0.1 second
}//****************************************************************

The LED flickers faster through the test result, therefore, pins and delay time affect flash frequency.

Project 2: Adjust LED Brightness

(1)Description

In previous lesson, we control LED on and off and make it blink.
In this project, we will control LED brightness through PWM to simulate breathing effect. Similarly, you can change the step length and delay time in the code so as to demonstrate different breathing effect.
PWM is a means of controlling the analog output via digital means. Digital control is used to generate square waves with different duty cycles (a signal that constantly switches between high and low levels) to control the analog output.In general, the input voltage of port are 0V and 5V. What if the 3V is required? Or what if switch among 1V, 3V and 3.5V? We can’t change resistor constantly. For this situation, we need to control by PWM.

For the Arduino digital port voltage output, there are only LOW and HIGH, which correspond to the voltage output of 0V and 5V. You can define LOW as 0 and HIGH as 1, and let the Arduino output five hundred 0 or 1 signals within 1 second. If output five hundred 1, that is 5V; if all of which is 1, that is 0V. If output 010101010101 in this way then the output port is 2.5V, which is like showing movie. The movie we watch are not completely continuous. It actually outputs 25 pictures per second. In this case, the human can’t tell it, neither does PWM. If want different voltage, need to control the ratio of 0 and 1. The more 0,1 signals output per unit time, the more accurately control.

(2)Equipment

(3)Hook-up Diagram

(4)Test Code：

/*
 keyestudio 4wd BT Car V2
 lesson 2.1
 pwm
 http://www.keyestudio.com
*/
int ledPin = 3; // Define the LED pin at D3
int value;
void setup () {
  pinMode (ledPin, OUTPUT); // initialize ledpin as an output.
}
void loop () {
  for (value = 0; value <255; value = value + 1) {
    analogWrite (ledPin, value); // LED lights gradually light up
    delay (5); // delay 5MS
  }
  for (value = 255; value> 0; value = value-1) {
    analogWrite (ledPin, value); // LED gradually goes out
    delay (5); // delay 5MS
  }
}

(5) Test Result

Upload test code successfully, LED gradually becomes brighter then darker, like human breath, rather than light on and off immediately.

(6)Code Explanation

When we need to repeat some statements, we could use FOR statement.
FOR statement format is shown below:

FOR cyclic sequence: Round 1：1 → 2 → 3 → 4 Round 2：2 → 3 → 4 … Until number 2 is not established, “for”loop is over, After knowing this order, go back to code: for (int value = 0; value < 255; value=value+1){

...

} for (int value = 255; value >0; value=value-1){

...

}

The two“for”statements make value increase from 0 to 255, then reduce from 255 to 0, then increase to 255,....infinitely loop There is a new function in the following ----- analogWrite() We know that digital port only has two state of 0 and 1. So how to send an analog value to a digital value? Here,this function is needed. Let’s observe the Arduino board and find 6 pins marked“~”which can output PWM signals.
Function format as follows:
analogWrite(pin,value) analogWrite() is used to write an analog value from 0~255 for PWM port, so the value is in the range of 0~255. Attention that you only write the digital pins with PWM function, such as pin 3, 5, 6, 9, 10, 11.
PWM is a technology to obtain analog quantity through digital method. Digital control forms a square wave, and the square wave signal only has two states of turning on and off (that is, high or low levels). By controlling the ratio of the duration of turning on and off, a voltage varying from 0 to 5V can be simulated. The time turning on(academically referred to as high level) is called pulse width, so PWM is also called pulse width modulation.
Through the following five square waves, let’s acknowledge more about PWM.

In the above figure, the green line represents a period, and value of analogWrite() corresponds to a percentage which is called Duty Cycle as well. Duty cycle implies that high-level duration is divided by low-level duration in a cycle. From top to bottom, the duty cycle of first square wave is 0% and its corresponding value is 0. The LED brightness is lowest, that is, turn off. The more time high level lasts, the brighter the LED.
Therefore, the last duty cycle is 100%, which correspond to 255, LED is brightest. 25% means darker.
PWM mostly is used for adjusting the LED brightness or rotation speed of motor.
It plays vital role in controlling smart robot car. I believe that you can’t wait to enter next project.

(7) Extension Practice：
Let’s modify the value of delay and remain the pin unchanged, then observe how LED changes.

/*
 keyestudio 4wd BT Car V2
 lesson 2.2
 pwm
 http://www.keyestudio.com
*/
int ledPin = 3; // Define the LED pin at D3
void setup(){
  pinMode (ledPin, OUTPUT); // initialize ledpin as an output.
}
void loop(){
  for (int value = 0; value <255; value = value + 1){
    analogWrite (ledPin, value); // LED lights gradually light up
    delay (30); // delay 30MS
  }
  for(int value=255; value>0;value=value-1){
    analogWrite (ledPin, value); // LED gradually goes out
    delay (30); // delay 30MS
  }
}//**********************************************************

Upload code on the development board and LED gradually gets brighter then darker.

Project 3 : The working Principle of Line Tracking Sensor

(1) Description：

The tracking sensor is actually an infrared sensor. The component used here is the TCRT5000 infrared tube.
Its working principle is to use the different reflectivity of infrared light to the color, then convert the strength of the reflected signal into a current signal.
During the process of detection, black is active at HIGH level, but white is active at LOW level. The detection height is 0-3 cm.
Keyestudio 3-channel line tracking module has integrated 3 sets of TCRT5000 infrared tube on a single board, which is more convenient for wiring and control.
By rotating the adjustable potentiometer on the sensor, it can adjust the detection sensitivity of the sensor.

(2) Specification：

Operating Voltage: 3.3-5V (DC)
Interface: 5PIN
Output Signal: Digital signal
Detection Height: 0-3 cm

Special note: before testing, turn the potentiometer on the sensor to adjust the detection sensitivity. When adjust the LED at the threshold between ON and OFF, the sensitivity is the best.

(3)Equipment：

(4)Connection Diagram：

(5)Test Code：

/*
keyestudio 4wd BT Car V2
lesson 3.1 
 Line Track sensor
 http://www.keyestudio.com
*/
int L_pin = 6;  //pins of  left line tracking sensor
int M_pin = 7;  //pins of  middle line tracking sensor
int R_pin = 8;  //pins of  right  line tracking sensor
int val_L,val_R,val_M;// define these variables
void setup()
{
  Serial.begin(9600); // initialize serial communication at 9600 bits per second
  pinMode(L_pin,INPUT); // make the L_pin as an input
  pinMode(M_pin,INPUT); // make the M_pin as an input
  pinMode(R_pin,INPUT); // make the R_pin as an input
}
void loop() 
{ 
  val_L = digitalRead(L_pin);//read the L_pin:
  val_R = digitalRead(R_pin);//read the R_pin:
  val_M = digitalRead(M_pin);//read the M_pin:
  Serial.print("left:");
  Serial.print(val_L);
  Serial.print(" middle:");
  Serial.print(val_M);
  Serial.print(" right:");
  Serial.println(val_R);
  delay(500);// delay in between reads for stability
}//***************************************************************************

(6)Test Result：
Upload the code on development board, open serial monitor to check line tracking sensors. And the displayed value is 1(high level) when no signals are received. The value becomes int o 0 when covering sensor with paper.

(7)Code Explanation
Serial.begin(9600)- Initialize serial port, set baud rate to 9600 pinMode- Define the pin as input or output mode digitalRead-Read the state of pin, which are generally HIGH and LOW level

(8)Extension Practice
After knowing its working principle, connect an LED to D3. We could control LED by line tracking sensor.

Test Code

/*
keyestudio 4wd BT Car V2
lesson 3.2
 Line Track sensor
 http://www.keyestudio.com
*/
int L_pin = 6;  //pins of  left line tracking sensor
int M_pin = 7;  //pins of  middle line tracking sensor
int R_pin = 8;  //pins of  right  line tracking sensor
int val_L,val_R,val_M;// define the variables of three sensors 
void setup()
{
  Serial.begin(9600); // initialize serial communication at 9600 bits per second
  pinMode(L_pin,INPUT); // make the L_pin as an input
  pinMode(M_pin,INPUT); // make the M_pin as an input
  pinMode(R_pin,INPUT); // make the R_pin as an input
  pinMode(3, OUTPUT);
}
void loop() 
{ 
  val_L = digitalRead(L_pin);//read the L_pin:
  val_R = digitalRead(R_pin);//read the R_pin:
  val_M = digitalRead(M_pin);//read the M_pin:
  Serial.print("left:");
  Serial.print(val_L);
  Serial.print(" middle:");
  Serial.print(val_M);
  Serial.print(" right:");
  Serial.println(val_R);

  if (val_L == HIGH)//if left line tracking sensor detects signals
  { 
    digitalWrite(3, LOW);//LED is off
  } 
  else/if left line tracking sensor doesn’t detect signals
  { 
    digitalWrite(3, HIGH);//LED lights up
    delay(2000); 
  }
   
  if (val_R == HIGH)//if right line tracking sensor detects signals
  {
    digitalWrite(3, LOW);//LED is off
  }
  else//if right line tracking sensor doesn’t detect signals
  {
    digitalWrite(3, HIGH);//LED lights up
    delay(2000); 
  }
    
  if (val_M == HIGH)//if middle line tracking sensor detects signals
  {
    digitalWrite(3, LOW);//LED is off
  }
  else//if middle line tracking sensor doesn’t detect signals
  {
    digitalWrite(3, HIGH);//LED lights up
    delay(2000); 
  }
}
//****************************************************************************

Upload the code to development board, we could observe the brightness of LED when covering the line tracking sensor or getting close to it by hand

Project 4: Servo Control

(1)Description

Servo motor is a position control rotary actuator. It mainly consists of housing, circuit board, core-less motor, gear and position sensor. Its working principle is that the servo receives the signal sent by MCU or receiver and produces a reference signal with a period of 20ms and width of 1.5ms, then compares the acquired DC bias voltage to the voltage of the potentiometer and obtain the voltage difference output.

When the motor speed is constant, the potentiometer is driven to rotate through the cascade reduction gear, which leads that the voltage difference is 0, and the motor stops rotating. Generally, the angle range of servo rotation is 0° --180 °

The rotation angle of servo motor is controlled by regulating the duty cycle of PWM (Pulse-Width Modulation) signal. The standard cycle of PWM signal is 20ms (50Hz). Theoretically, the width is distributed between 1ms-2ms, but in fact, it's between 0.5ms-2.5ms. The width corresponds the rotation angle from 0° to 180°. But note that for different brand motor, the same signal may have different rotation angle.

The corresponding servo angles are shown below:

(2)Specification

Working voltage: DC 4.8V ~ 6V
Operating angle range: about 180 ° (at 500 → 2500 μsec)
Pulse width range: 500 → 2500 μsec
No-load speed: 0.12 ± 0.01 sec / 60 (DC 4.8V) 0.1 ± 0.01 sec / 60 (DC 6V)
No-load current: 200 ± 20mA (DC 4.8V) 220 ± 20mA (DC 6V)
Stopping torque: 1.3 ± 0.01kg · cm (DC 4.8V) 1.5 ± 0.1kg · cm (DC 6V)
Stop current: ≦ 850mA (DC 4.8V) ≦ 1000mA (DC 6V)
Standby current: 3 ± 1mA (DC 4.8V) 4 ± 1mA (DC 6V)

(3)Equipment

(4)Connection Diagram：

Wiring note: the brown line of servo is linked with Gnd(G), the red line is connected to 5v(V) and orange line is attached to digital 10.

The servo has to be connected to external power due to its high demand for driving servo current. Generally, the current of development board is not enough. If without connected power, the development board could be burnt.

(5)Test Code1

/*
keyestudio 4wd BT Car V2
lesson 4.1
Servo
http://www.keyestudio.com
*/
#define servoPin 10  //servo Pin
int pos; //the angle variable of servo
int pulsewidth; // pulse width variable of servo
void setup() {
  pinMode(servoPin, OUTPUT);  //set the pins of servo to output
  procedure(0); // set the angle of servo to 0 degree
}
void loop() {
  for (pos = 0; pos <= 180; pos += 1) { // goes from 0 degrees to 180 degrees
    // in steps of 1 degree
    procedure(pos);              // tell servo to go to position in variable 'pos'
    delay(15);                   //control the rotation speed of servo

  }
  for (pos = 180; pos >= 0; pos -= 1) { // goes from 180 degrees to 0 degrees
    procedure(pos);              // tell servo to go to position in variable 'pos'
    delay(15);                    
  }}
// function to control servo
void procedure(int myangle) {
  pulsewidth = myangle * 11 + 500;  //calculate the value of pulse width
  digitalWrite(servoPin,HIGH);
  delayMicroseconds(pulsewidth);   //The duration of high level is pulse width
  digitalWrite(servoPin,LOW);
  delay((20 - pulsewidth / 1000));  // the cycle is 20ms, the low level last for the rest of time
}//**********************************************************************************

Upload code successfully, servo swings back in the range of 0° to 180°

There is another guide for restraining servo---- servo library file, the following link of official website is for your reference. https://www.arduino.cc/en/Reference/Servo

The library file of servo is used in the following code

(6)Test Code2

/*
 keyestudio 4wd BT Car V2
 lesson 4.2
 servo
 http://www.keyestudio.com
*/
#include <Servo.h>
Servo myservo;  // create servo object to control a servo
// twelve servo objects can be created on most boards
int pos = 0;    // variable to store the servo position
void setup() {
  myservo.attach(10);  // attaches the servo on pin 9 to the servo object
}
void loop() {
  for (pos = 0; pos <= 180; pos += 1) { // goes from 0 degrees to 180 degrees
    // in steps of 1 degree
    myservo.write(pos);              // tell servo to go to position in variable 'pos'
    delay(15);                       // waits 15ms for the servo to reach the position
  }
  for (pos = 180; pos >= 0; pos -= 1) { // goes from 180 degrees to 0 degrees
    myservo.write(pos);              // tell servo to go to position in variable 'pos'
    delay(15);                       // waits 15ms for the servo to reach the position
  }}//************************************************************************

(7)Test Result
Upload code successfully and power on, servo swings in the range of 0° to 180°. The result is same. We usually control it by library file.

(8) Code Explanation
Arduino comes with #include <Servo.h> (servo function and statement）
The following are some common statements of the servo function:
1. attach（interface）——Set servo interface, port 9 and 10 are available

2. write（angle）——The statement to set rotation angle of servo, the angle range is from 0° to 180°
3. read（）——The statement to read angle of servo, read the command value of “write()”
4. attached（）——Judge if the parameter of servo is sent to its interface
Note: The above written format is“servo variable name, specific statement（）”, for instance: myservo.attach(9)

Project 5: Ultrasonic Sensor

(1)Description

The HC-SR04 ultrasonic sensor uses sonar to determine distance to an object like bats do. It offers excellent non-contact range detection with high accuracy and stable readings in an easy-to-use package. It comes complete with ultrasonic transmitter and receiver modules.
The HC-SR04 or the ultrasonic sensor is being used in a wide range of electronics projects for creating obstacle detection and distance measuring application as well as various other applications. Here we have brought the simple method to measure the distance with arduino and ultrasonic sensor and how to use ultrasonic sensor with arduino.

(2)Specification

Power Supply :+5V DC
Quiescent Current : <2mA
Working Current: 15mA
Effectual Angle: <15°
Ranging Distance : 2cm – 400 cm
Resolution : 0.3 cm
Measuring Angle: 30 degree
Trigger Input Pulse width: 10uS

(3)Equipment

(4)The principle of ultrasonic sensor
As the above picture shown, it is like two eyes. One is transmitting end, the other is receiving end.

The ultrasonic module will emit the ultrasonic waves after trigger signal. When the ultrasonic waves encounter the object and are reflected back, the module outputs an echo signal, so it can determine the distance of object from the time difference between trigger signal and echo signal.
The t is the time that emitting signal meets obstacle and returns.
and the propagation speed of sound in the air is about 343m/s, therefore, distance = speed * time, because the ultrasonic wave emits and comes back, which is 2 times of distance, so it needs to be divided by 2, the distance measured by ultrasonic wave = (speed * time)/2

1.Use method and timing chart of ultrasonic module:
Setting the delay time of Trig pin of SR04 to 10μs at least, which can trigger it to detect distance.
2. After triggering, the module will automatically send eight 40KHz ultrasonic pulses and detect whether there is a signal return. This step will be completed automatically by the module.
3. If the signal returns, the Echo pin will output a high level, and the duration of the high level is the time from the transmission of the ultrasonic wave to the return.

Circuit diagram of ultrasonic sensor:

(5)Connection Diagram

(6)Test Code

/*
 keyestudio 4wd BT Car V2
 lesson 5
 Ultrasonic sensor
 http://www.keyestudio.com
*/ 
int trigPin = 12;    // Trigger
int echoPin = 13;    // Echo
long duration, cm, inches;
 void setup() {
  //Serial Port begin
  Serial.begin (9600);
  //Define inputs and outputs
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}
void loop() {
  // The sensor is triggered by a HIGH pulse of 10 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
   // Read the signal from the sensor: a HIGH pulse whose
  // duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  duration = pulseIn(echoPin, HIGH);
   // Convert the time into a distance
  cm = (duration/2) / 29.1;     // Divide by 29.1 or multiply by 0.0343
  inches = (duration/2) / 74;   // Divide by 74 or multiply by 0.0135
    Serial.print(inches);
  Serial.print("in, ");
  Serial.print(cm);
  Serial.print("cm");
  Serial.println();
  delay(50);
}
//**************************************************************************

(7)Test Result

Upload test code on the development board, open serial monitor and set baud rate to 9600. The detected distance will be displayed, unit is cm and inch. Hinder the ultrasonic sensor by hand, the displayed distance value is smaller.

(8)Code Explanation

int trigPin- this pin is defined to transmit ultrasonic waves, generally output.
int echoPin - this is defined as the pin of reception, generally input
cm = (duration/2) / 29.1-
inches = (duration/2) / 74-
We can calculate the distance by using the following formula:
distance = (traveltime/2) x speed of sound
The speed of sound is: 343m/s = 0.0343 cm/uS = 1/29.1 cm/uS
Or in inches: 13503.9in/s = 0.0135in/uS = 1/74in/uS
We need to divide the traveltime by 2 because we have to take into account that the wave was sent, hit the object, and then returned back to the sensor.

(9)Extension Practice:

We have just measured the distance displayed by the ultrasonic. How about controlling the LED with the measured distance? Let's try it, connect an LED light module to the D3pin.

/*
 keyestudio 4wd BT Car V2
 lesson 5.2
 Ultrasonic LED
 http://www.keyestudio.com
*/ 
int trigPin = 12;    // Trigger
int echoPin = 13;    // Echo
long duration, cm, inches;
void setup() {
  Serial.begin (9600);  //Serial Port begin
  pinMode(trigPin, OUTPUT);  //Define inputs and outputs
  pinMode(echoPin, INPUT);
  pinMode(3, OUTPUT);
}
 void loop() 
{
  // The sensor is triggered by a HIGH pulse of 10 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  // Read the signal from the sensor: a HIGH pulse whose
  // duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  duration = pulseIn(echoPin, HIGH);
  // Convert the time into a distance
  cm = (duration/2) / 29.1;     // Divide by 29.1 or multiply by 0.0343
  inches = (duration/2) / 74;   // Divide by 74 or multiply by 0.0135
  Serial.print(inches);
  Serial.print("in, ");
  Serial.print(cm);
  Serial.print("cm");
  Serial.println();
  delay(50);
if (cm>=2 && cm<=10)digitalWrite(3, HIGH);
else digitalWrite(3, LOW);
}//****************************************************************

Upload test code to development board and block ultrasonic sensor by hand, then check if LED is on.

Project 6: IR Reception

(1)Description

There is no doubt that infrared remote control is ubiquitous in daily life. It is used to control various household appliances, such as TVs, stereos, video recorders and satellite signal receivers. Infrared remote control is composed of infrared transmitting and infrared receiving systems, that is, an infrared remote control and infrared receiving module and a single-chip microcomputer capable of decoding.
The 38K infrared carrier signal emitted by remote controller is encoded by the encoding chip in the remote controller. It is composed of a section of pilot code, user code, user inverse code, data code, and data inverse code. The time interval of the pulse is used to distinguish whether it is a 0 or 1 signal and the encoding is made up of these 0, 1 signals.
The user code of the same remote control is unchanged. The data code can distinguish the key.
When the remote control button is pressed, the remote control sends out an infrared carrier signal. When the IR receiver receives the signal, the program will decode the carrier signal and determines which key is pressed. The MCU decodes the received 01 signal, thereby judging what key is pressed by the remote control.
Infrared receiver we use is an infrared receiver module. Mainly composed of an infrared receiver head, it is a device that integrates reception, amplification, and demodulation. Its internal IC has completed demodulation, and can achieve from infrared reception to output and be compatible with TTL signals. Additionally, it is suitable for infrared remote control and infrared data transmission. The infrared receiving module made by the receiver has only three pins, signal line, VCC and GND. It is very convenient to communicate with arduino and other microcontrollers.

(2)Specification

Operating Voltage: 3.3-5V（DC）
Interface: 3PIN
Output Signal: Digital signal
Receiving Angle: 90 degrees
Frequency: 38khz
Receiving Distance: 10m

(3)Equipment

(4)Connection Diagram

Respectively link“-”,“+”and S of IR receiver module with G(GND）, V（VCC）and A0 of keyestudio development board.
Attention: On the condition that digital ports are not available, analog ports can be regarded as digital ports. A0 equals to D14, A1 is equivalent to digital 15.

(5)Test Code
Firstly import library file of IR receiver module(refer to how to import Arduino library file) before designing code.

/*
 keyestudio 4wd BT Car V2
 lesson 6.1
 IRremote
 http://www.keyestudio.com
*/ 
#include <IRremote.h>     // IRremote library statement
int RECV_PIN = A0;        //define the pins of IR receiver as A0
IRrecv irrecv(RECV_PIN);   
decode_results results;   // decode results exist in the“result” of “decode results”
void setup()  
	{  
      Serial.begin(9600);  
      irrecv.enableIRIn(); // Enable receiver
	}  
 void loop() {  
	  if (irrecv.decode(&results))//decode successfully, receive a set of infrared signals
	  {  
	    Serial.println(results.value, HEX);//Wrap word in 16 HEX to output and receive code 
	    irrecv.resume(); // Receive the next value
	  }  
	  delay(100);  
	} //*******************************************************

(6)Test Result
Upload test code, open serial monitor and set baud rate to 9600, point remote control to IR receiver and the corresponding value will be shown, if pressing so long, the error codes will appear.

Below we have listed out each button value of keyestudio remote control. So you can keep it for reference.

(7) Code Explanation
irrecv.enableIRIn(): after enabling IR decoding, the IR signals will be received, then function“decode()”will check continuously if decode successfully.

irrecv.decode(&results): after decoding successfully, this function will come back to “true”, and keep result in “results”. After decoding a IR signals, run the resume()function and receive the next signal.

(8)Extension Practice

We decoded the key value of IR remote control. How about controlling LED by the measured value? We could operate an experiment to affirm. Attach an LED to D3, then press the keys of remote control to make LED light up and off.

/* keyestudio 4wd BT Car V2
lesson 6.2
IRremote
http://www.keyestudio.com
*/ 
#include <IRremote.h>
int RECV_PIN = A0;//define the pin of IR receiver as A0
int LED_PIN=3;// define the pin of LED as pin 3
int a=0;
IRrecv irrecv(RECV_PIN);
decode_results results;
void setup()
{Serial.begin(9600);
  irrecv.enableIRIn(); //  Initialize the IR receiver 
  pinMode(LED_PIN,OUTPUT);//set pin 3 of LED to OUTPUT
}
void loop() {
  if (irrecv.decode(&results)) {
if(results.value==0xFF02FD &a==0) //according to the above key value, press“OK”on remote control , LED will be controlled
{digitalWrite(LED_PIN,HIGH);//LED will be on
a=1;
}
else if(results.value==0xFF02FD &a==1) //press again
{
digitalWrite(LED_PIN,LOW);//LED will go off
a=0;
}
    irrecv.resume(); // receive the next value
  }}//*******************************************************

Upload code to development board, press“OK”key on remote control to make LED on and off.

KS0470 Keyestudio 4WD BT Robot Car V2.0 Kit for Arduino

Contents

Introduction

Features

Specification

Product List

Assembly Guide

6. Install Arduino IDE and Driver

Download software

Installing driver

7. How to Add a Library?

8. Projects

Project 1: LED Blink

Project 2: Adjust LED Brightness

Project 3 : The working Principle of Line Tracking Sensor

Project 4: Servo Control

Project 5: Ultrasonic Sensor

Project 6: IR Reception

Navigation menu

KS0470 Keyestudio 4WD BT Robot Car V2.0 Kit for Arduino

Introduction

Features

Specification

Product List

Assembly Guide

6. Install Arduino IDE and Driver

Download software

Installing driver

7. How to Add a Library?

8. Projects

Project 1: LED Blink

Project 2: Adjust LED Brightness

Project 3 : The working Principle of Line Tracking Sensor

Project 4: Servo Control

Project 5: Ultrasonic Sensor

Project 6: IR Reception

Navigation menu

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