Designing A Parking System Using Arduino And IR Sensors

1. Apply the principles of good measurement and instrumentation practice.
2. Select appropriate sensors according to the engineering required and operating circumstances.
3. Process sensor data which is contaminated by noise by use of statistic data processing methods.
4. Test and evaluate sensors and measurement systems.

5. Design real time data acquisition systems including sensor interface, signal conditioning and signal digitizing

Components Used

Conventional parking systems involved less precision, risks of accidents and time consuming. A driver has to be professional in parking because it involved awareness of the surrounding, estimation of the distance between the vehicle and the wall. However, a professional can also make mistakes using conventional methods. In some cases an invigilators help is taken for assisting. In all it as unreliable and needs to be replaced by some modern method. 

This project involves the use of Arduino Uno R3, built around Atmel’s powerful MCU- Atmega328p which is an 8-bit microcontroller. IR GP2Y0A21YK0F infrared distance measuring sensor developed by ‘Sharp’. It is an easy to work sensor, operating in the range of 10 cm to 80 cm. It is cheap. So, in all combining both the devices resulted in a powerful and accurate parking system. This device can be installed in the car and due to its small size it is quite handy as well. LCD adds on the value. Here, an alphanumeric 16x2 LCD named LM016L, is used. For extra safety a piezo buzzer is also used which produces two different sound of different frequency.

A car manufacturing company is requested to design a distance measurement system using IR distance sensor (Model No. GP2Y0A21YK0F) to support the auto park car feature. The sensor should start giving alarm when the car is around 80 cm away from the wall. Alarm tone should be varied with distance.

Design an appropriate alarm system to detect the distance change. Plot the relation between the distance and the sensor output voltage (Use any possible graph tool).  

It is used in popularly in robotics. It has a wide range of 10 cm to 80 cm. It is cheap, unlike the costly sonar distance finders. It is highly accurate and small in size making it a popular choice among the developers. It works on the principle of Infrared technology, having a transmitter to transmit the infrared light on the object and a receiver to receive it. It is a 3 pin device of which the red one is for power, black for ground and the third is the sensor output line. Its operating voltage is between 4.5V to 5.5V. This range makes it easy to work with microcontrollers. The output voltage lies between 0.4V to 3V. The current consumption is 30 mA. The output voltage is dependent on the distance being measured by it. If the distance is 10cm, the corresponding output voltage will be 3V (maximum) and if the distance is 80cm, the corresponding output voltage will be 0.4V.  

Output voltage(in V)	Distance from the obstacle(in cm)
0	0
0.1	1
0.3	2
0.5	2.5
0.6	3
0.8	3.5
1	4
1.3	5
3	10
1.5	20
1	30
0.7	40
0.6	50
0.5	60
0.4	70
0.3	80

Table 1

The plot between the output voltage and the distance from the obstacle is approximately linear in the working range. But, a sudden jump is observed at 0cm. The graph follows a straight line from 0cm to 0.4cm and reaches 3V. But, this range is not considered in the measurement. Talking about the operating range, there is a gradual slope as the distance in increasing.  The distance at any output voltage can be determined by creating a best fit line between the inverse of the voltage and the distance. All in all, a constant scaling factor approximately equal to 30, divided by the output voltage gives the desired distance (Pololu, 2018).

IR GP2Y0A21YK0F Infrared Distance Measuring Sensor

So, Distance from the obstacle= 30/ Sensor voltage.

For example, if the sensor voltage is 3V, then the corresponding distance can be calculated using the above formula,

Distance from the obstacle= 30/ 3= 10 cm.

Similarly, if the output voltage is coming out to be 0.4V, then the corresponding distance will be,

Distance from the obstacle= 30/0.4= 75cm.

We have taken the limits in this case to demonstrate. Note that there might be some errors because we have approximated the graph to a linear one, this formula can be improved by considering it to a non- linear graph only but that requires some serious high level mathematics.

A signal conditioning circuit should be developed that considers the sensor output voltage from 0.4V to 3Vto operate the alarm. Assume that the sensor signal output is digitized using an appropriate 8 bit A-D converter which derive from the microprocessor or microcontroller. An appropriate distance display should be provided.

One of the most popular development boards, ‘Arduino Uno R3’ which is built around Atmega328p MCU serves the best purpose for achieving the desired result. Arduino Uno R3 has 14 digital pins which can be used either for input or output. The behavior of the pins can be changed via coding. Out of these 20 digital pins 6 are analog input pins (A0, A1, A2, A3, A4 and A5) and as PWM pins. It runs with the help of a crystal oscillator of 16 MHz frequency. A USB port for programming and powering the board is also provided along with a separate dc jack. The input via dc jack is regulated to the TTL levels by the regulators. Moreover, a battery can also be used for powering Arduino Uno R3. Its operating voltage is between 7V to 12V. Arduino Uno R3 is special and different from other boards because it does not use FTDI USB- serial converter. In place of it there is an in built programmer. It also has its own bootloader.

Arduino is an open source project which means that any developer from any corner of the world can contribute his/her programming skills for the growth (Sarwar, 2016). This is already being done as Arduino boasts of one of the most active forums comprising experts who have already done their hands dirty in coding. Arduino Uno R3 is built around ATMEGA328P chip (Intorobotics, 2013), (Tutorials Point, 2018).

It provides a 32kb of in built and programmable flash that has both the read as well as write capabilities, 16kb of RAM, 20 input and output pins, 16 external interrupts, real time clock, watch dog timer, Two 8-bit timers/ counters, it can provide a maximum of 10 bit resolution via ADC converter (SnapEDA, 2018). 

Our focus is primarily on this is the ADC converter with 6 channels are multiplexed with it from the respective analog lines. We will be using it in 8 bit resolution mode. There is a sample and hold circuit that makes the input voltage to the ADC constant during the analog to digital conversion. There is also an A _ref and AV _cc pin. The reference pin indicates the maximum analog voltage that can be measured using the ADC converter. Since the operating voltage should be around 5V, so the reference voltage is usually given as 5V supply. The reference voltage chosen affects the precision of the DC converter. The meaning of 8 bit resolution is that 2⁸= 256 different levels are available to assign the measured voltage ranging from 0 to 5 V given as analog voltage. But, if a 2V voltage supply is provide to the reference, the number of discrete levels that would still be same but now minute voltages can also be assigned the level, which in the case of 5V was not possible. This way the precision is greatly increased. But, with every great thing comes the bad too. There is no bad thing in this case but a restriction that we cannot measure a signal whose voltage is more than 2V. Those will simply be rejected by the MCU. So, at the cost of little diversion from accuracy, we use 5V supply as this increases the measuring capacity of the microcontroller. A V _cc is the supply pin for the ADC of the microcontroller. It is given as 5V (Learning About Electronics, 2018), (Hienzsch, 2015). 

Table 1

Resolution/ reference voltage = ADC value/ analog input voltage (Sparkfun, 2018) 

For example, if the reference voltage is 5V, the given input analog voltage is 3V and the resolution is 256, then the ADC value assigned to it will be, 

ADC value= (Resolution* analog input voltage)/ reference voltage

That is, ADC value= (256* 3)/ 5 = 153 (integers only)  

Suppose, the reference voltage is 3V, the given input analog voltage is also 3V and the resolution is 256, then the ADC value assigned to it will be,   

ADC value= (Resolution* analog input voltage)/ reference voltage

That is, ADC value= (256* 3)/ 3 = 256 

Note that in the case of reference voltage equal to 3 volts, there are more number of levels available to be assigned to the voltage up to 3V. 256 is greater than 153 this simply means that the voltages less than 3 volts can be assigned in 255 levels, while if the reference is 5V, only 152 levels can be assigned to voltages less than 3 volts. This clearly reflects the precision of ADC. 

The sensitivity of any instrument is defined as the smallest amount of change it can detect. This device records the sensor voltage up to two decimal places. So, the minimum change it can detect is 0.01 volts. If the input voltage is below 0.01 volts it can’t be sensed by this device

Least count of any instrument is the minimum reading it can take. In this case the minimum value of voltage that can be measured is 0.01 volts. So the Least Count (LC) = 0.01V

In this project although the maximum voltage that can be measured is 5V because the reference is taken as 5V. But, the maximum voltage that the sensor can deliver is 3V. In order to calculate the accuracy of this device we need to record some real time values. Some of the values are shown in table 2. The values in the column 1 are voltages values measured by the device from the sensor, while column 2 shows the actual voltages measured through voltmeter..

Measured values (in volts)	Actual voltage (in volts)
2.91	3.89
2.86	2.84
2.71	2.69
2.11	2.09
1.50	1.50
1.10	1.10
0.65	0.64
0.60	0.59
0.55	0.54
0.45	0.45

Table 2

Adding all the measured values by the device, we get = 2.91+ 2.86 + 2.71 + 2.11 + 1.50 + 1.10 + 0.65 + 0.60 + 0.55 + 0.45 = 15.44

Since, the average value = Sum of the values/ total number of values

Here, sum of the values = 15.44 and the total number of values = 10

So, Average = 15.44/10 = 1.54

Similarly, adding the actual voltage values = 3.89 + 2.84 + 2.69 + 2.09 + 1.50 + 1.10 + 0.64 + 0.59 + 0.54 + 0.45 = 16.33

Since, the average value = Sum of the values/ total number of values

Here, sum of the values = 16.33 and the total number of values = 10

So, Average = 16.33/10 = 1.63

Now, calculating the difference = Average actual value – average measured value = 1.63 – 1.54 = 0.09

So, the percentage error = (Difference in the value/ average of the actual value) * 100

Signal Conditioning Circuit

= (0.09/ 1.63) * 100 = 5.5%

It has 1 controller, 14 pins, it comes with a backlit feature as well increasing its applicability in the dark situations as well so for this 2 extra pins have been provided and it supports 80 characters (Margaret, 2005). The characters are alphanumeric in nature. It has 2 rows and 16 columns to display the characters (Kushagra, 2012).

The pin description is shown in the table 1.

Pin no.	Pin name	Description
1	VSS	Ground
2	VCC	Supply (5V)
3	VEE	Contrast
4	RS	‘0’ for instruction input ‘1’ for data input
5	R/W	‘0’ to write into LCD ‘1’ to read from LCD
6	EN	Enable input
7	D0	Data bus 0 (LSB)
8	D1	Data bus 1
9	D2	Data bus 2
10	D3	Data bus 3
11	D4	Data bus 4
12	D5	Data bus 5
13	D6	Data bus 6
14	D7	Data bus 7 (MSB)

Table 1 (Prasad, 2018)

Various components of LM016L are discussed below,

DDRAM- Display Data RAM:

It stores the character of the data. Its maximum capacity is 80, meaning that it can hold 80 characters at a time. Since each character is of 8 bits, therefore it holds a maximum of 640 bits. In 16x2 LCD, only 32 characters can be displayed at a time so DDRAM stores those characters as well which are not provided for displaying. These characters are not visible to the users. 

CGOM RAM:

The ASCII characters entered by the user is displayed with the help of CGOM RAM after being stored in DDRAM.

CGRAM:

It helps in making custom characters as well as animation in them.

BF:

Busy Flag indicates whether the LCD is busy or not. Whenever a user gives any command or data to the LCD it is being processed after some time. Obviously this time is of milliseconds in the world of microcontrollers, but still it is a delay. So before giving any data or command, BF should be read and this can be read only when RS is ‘0’ and R/W is ‘1’. In this case the D7 acts as BF.

Instruction and data registers:

As the name implies, the instruction register stores the commands and the data register stores the data to be displayed. Instructions include clearing operation, next line, setting a cursor at a particular point on the display etc. 

Before performing any action the LCD needs to be initialized. This is possible by two ways, either by the internal circuit to reset the module or the set of initializing commands. The mode is decided by the user. 

In this project we will be using the LCD in 4 bit mode, only 4 data bits will be sufficient to serve the purpose. Lesser pins to interface means less complexity.

 In the 4 bit mode, data is sent in nibbles, a set of 4 bits. But before sending them we need to inform LCD that we have switched to 4 bit mode. 

Piezo electric buzzers work on the principle of piezoelectricity to produce sound.  

They are used almost everywhere wherever microphones are involved. The term basically means pressing electricity. The piezo buzzers convert mechanical energy to electrical energy and vice versa as well. Piezoelectricity is a phenomenon in which the crystal is deformed when an external voltage is applied across its ends. Due to this deformations it starts vibrating. The vibrations produced depends on the intensity of applied voltage across the ends. Hence, application of voltage of different magnitudes produce vibrations of different frequencies and hence we hear different sounds. The reverse is also true when the crystal is deformed or stress is applied across its ends, a potential difference is generated. If the two ends are connected, current also starts flowing. Thus, we can say that piezo electric materials are a sort of small batteries (Adafruit, 2018). 

Arduino Uno R3 Board

Piezo electric materials are the form of crystals. Now, we are very much familiar with the crystals that they have some repeating structures, orderly arranged manner. But, it does not holds for piezo crystals. Metals are an example of crystals following the conventional definition, but piezo electric crystals are not orderly arranged, instead they are electrically neutral. This means that positive charge or some half exactly cancels out the negative half of some other half. So, when an external voltage is applied across its ends, it makes the crystal polarized disturbing the Neutral behavior. To overcome this the atoms rearrange themselves and due to this rearrangement it deforms. Similarly, when an external pressure is applied across the ends of the piezo electric crystal, the atoms displaces from their positions and due to this the inequality in the charge distribution occurs. Negative and positive charges distributes throughout the crystal in such a way that its one face or the end develops polarity, while the opposite face develops an opposite one (MohanKumar, 2012). This difference in the polarity is responsible for developing a potential difference across its ends and therefore conduction of current. This property increase their applicability and hence they are used as a transducer. The transducers are devices that converts energy from one form to the other. Piezo electrical materials can be used to convert mechanical energy into electrical energy. This is seen in microphones. When a person speaks from one ends, due to the air molecules a pressure is exerted on the crystals. This develops electricity and hence the sound energy is converted into electrical energy. Another well- known reverse applicability is the speaker. In the speakers, when the electrical energy is supplied it deforms the crystal. Due to fluctuations, the vibrations also occur and these vibrations produce sound of different frequencies (Woodford, 2018). 

The piezo electric materials can be used as a diaphragm. Thin films are used with the base material. So, when the electric filed is applied in the surface of this element, it starts to vibrate. Its shape changes to and fro. This motion is rapid and continuous. Due to this motion the air particles also start to vibrate because they are in the direct contact with the atoms of the piezo electric film (APC International Ltd, 2018). The energy of vibration is transferred to them and as a result of this they also start vibrating along with the molecules of the piezo electric material (CUI Inc, 2018). This energy travels through air as a result of disturbance. These disturbances continues till they reach our ears (BBC News, 2005), (Scudellari, 2017), (Ross, 2017). 

The traditional speakers can be considered more like an inductive load rather than capacitive, whereas piezo electric buzzers can be considered more like capacitors when used to drive the circuits (Hughes, 2016).   

As shown in the figure 7, the piezo electric circuit is fairly simple to understand. An inductor of 10 micro henry, 100 kilo ohms and 10 kilo ohms resistors, an n-p-n transistor BC548 and a battery of the voltage 12V is used. The output if the collector goes to the main terminal of the buzzer, ground terminal is grounded to the common ground and the feedback terminal is connected to the 10kilo ohms resistor. The feedback line ensures that the voltage is applied continuously so that the vibrations do not stop until the external voltage is removed (Swag, 2018).   

ADC Converter and 8-Bit Resolution Mode

Arduino Uno R3 is chosen as the MCU, LM016L as the LCD module, a piezo buzzer for making sound and an IR GP2Y0A21YK0F infrared distance measuring sensor. As we can see the IR sensor module has three terminals namely the power, ground and the output voltage. The power terminal is connected to the 5V dc supply, ground is connected to the common ground and the output terminal to the analog input A0 of the Arduino Uno R3. The output of the sensor varies from 0.4V to 3V. The Arduino Uno R3 has got its ground connected internally to the common ground. The supply is also connected internally. The reference terminal of the analog to digital converter is connected to 5V. This makes this system capable of measuring voltages till 5V. The digital pins numbered from 2, 3, 4, 5, 6 and 7 are connected to the LCD module as shown. Pin 2 is connected to digital line 7 of the LCD, pin no. 3 to digital line 6, pin no. 4 to digital line 5 and the pin no. 5 to digital line 4 of the LCD. Note that as explained before we are using the LCD module in 4 bit mode because it is more than sufficient for the application. Pin no. 8 is connected to the positive end of the piezo buzzer. The VSS and the VEE pin of the LCD module is connected to the ground, VCC to 5V supply, enable pin goes to pin no. 6 and the RS pin goes to pin no. 7 of the Arduino Uno R3 board as shown. R/W pin is connected to the ground because LCD always listens the data in this case. The contrast pin can be connected to the ground via a potentiometer to adjust the contrast. The led pins marked as positive and negative in the LCD module are connected internally to power (5V) and ground respectively. These pins are for the backlight. Again they can be connected via a potentiometer but remember not to set any value that burns the led. The ground terminal of the piezo buzzer is connected to the common ground.    

The digital pin no. 8 is connected to the piezo buzzer. Through coding, desired frequency signal is transmitted to the buzzer which produces different sound as an output. When the range of distance is between 80 (inclusive) and 40 cm (exclusive), it buzz a low sound as compared to the sound when the distance becomes greater than 10 (inclusive) and less than 40 cm (inclusive). This high buzz is due to the fact that the car is getting near to the obstacle. Moreover, the distance as recorded is continuously being displayed on the LCD module for extra precaution. It displays the distance in cm as calculated by the formula discussed above. The analog value read by the sensor is converted to a discrete level which is again converted back to the voltage so that the sensor voltage is read. 

Let’s see the code used to understand it better,

(Hareendran, 2015)

(perez1028, 2013)

// Brake system of the car 

#include <LiquidCrystal.h>// including the Arduino LCD library

LiquidCrystal lcd(7,6,5,4,3,2); //defining the pins of the LCD in the order- LiquidCrystal lcd(rs,en,D4,D5,D6,D7)

int IR= A0;// connecting the Arduino analog pin A0 to the IR sensor

int buzzer= 8; // connecting the digital Arduino pin8 to the buzzer 

void setup()

{

  lcd.begin(16,2);

  pinMode(buzzer,OUTPUT); //defining as output pin

  digitalWrite(8,LOW); // initially making it low

  pinMode(IR,INPUT); // defining as input pin

}  

void loop() //loop begins

{

  lcd.clear(); // clears the screen

  float cc=analogRead(IR);

  float volts = (cc/4)*0.0196078431;  // value from sensor * (5/255)

  int distance = 30/volts;

  if (distance <= 80 && distance > 40) // condition

  {

    lcd.print("Dist="); // prints the string

    lcd.print(distance); // prints the distance value

    lcd.print(" cm"); // prints the unit

    delay(200);// delay for the execution of LCD commands

    tone(buzzer, 5000, 500); //plays sound of high 5000Hz frequency

  } 

  else if (distance <= 40 && distance >=10)// condition

  {

    lcd.print("Dist="); // prints the string

    lcd.print(distance); // prints the distance value

    lcd.print(" cm"); // prints the unit

    delay(200);// delay for the execution of LCD commands    

    tone(buzzer, 3000, 500); // plays sound of 3000Hz frequency

  }

  else // remaining condition

  {

    lcd.print("Out of range!"); // prints the string

    delay(200);// delay for the execution of LCD commands        

    tone(buzzer, 0, 500); // stops the sound in the normal condition   

  }

}

This code instructs the microcontroller to play the buzzing sound when the desired distance range is achieved. Firstly, the LCD libraries of the Arduino Uno R3 are included. These are the standard libraries and consists of all the functions such as passing of the strings, commands etc. This library makes the task easy and the commands that we will see after some time are as a result of this library. After this the LCD pins are initialized, the parameters are the pins and they are the passed to the function as shown. Note that the pin order has to be taken care as shown in the comments.

The sensor pin is connected to the analog pin A0 of the Arduino Uno R3 and so it’s an input pin while the buzzer is connected to the 8^th pin and it is an output pin. Note that two variables are defined of the type integer to hold the pin numbers. 

Setup function starts that executes only once throughout the code. Here, the initialization of the LCD is done. The IR pin is made an input pin by the command ‘pinMode (IR, INPUT)’ (Arduino, 2018). This command tells the Arduino Uno R3 that the following pin needs to be read. Since the reference and the power pins of the ADC are already connected to the supply, ADC is active and is ready to accept the voltage value. The buzzer pin is connected to the pin 8 of the Arduino Uno R3 and it is made an output pin by the command ‘pinMode (buzzer, OUTPUT)’ as shown.

In the loop section, all the instruction gets executed again and again. The LCD is cleared after each time it has displayed the distance (Arduino, 2018). The sensor out is read and is converted to the digital voltage back by multiplying the ADC value with 0.01960784315 (Arduino, 2018). Note that the same formula as we had discussed before is used here. This value or the voltage is converted to its corresponding distance using the formula discussed earlier. That is a constant factor is divided by the voltage obtained after conversion. It is then printed in the LCD using the LCD print commands. It is first printed, then some delay is added so that the instructions are executed properly. They are provided with some time for their execution. After this the condition is checked whether the car’s distance from the obstacle is lying between 40 and 80 cm. If found so the buzzer makes a sound of 5000Hz. This a loud sound and can be easily heard. It lies in the human audible range as well. If the distances comes out to be less than 40 cm then it’s a critical situation as the car may collide with the obstacle is not paid attention. If by chance he is unable to see the LCD, a more loud sound is generated by the piezo buzzer with a frequency of 3000Hz. This surely gets into the driver’s notice and he can avoid any accident. The function used here is tone (Arduino, 2018). This function generates frequency of oscillations of 50 percent duty cycle using the timer of the Arduino Uno R3. This timer works independent of the other timer and hence sound is bound to be produced even if LCD fails to operate in the case of emergency. This feature increases the strength of this project. 

Here, ISIS Proteus is used and it serves a great purpose. It is an industrial simulation tools, extremely powerful and easy to use. It comes with a wide range of libraries that cover almost all the electronics. It even comes with a virtual serial monitor to make it a real time simulation system (Labcenter Electronics Ltd, 2018).

Conclusion

From this project it can be easily concluded that traditional braking system needs to be replaced by the new and modern systems. There are many risks involved with the use of conventional braking systems such as the lack of estimation power while parking the vehicle. A person may not know the gap between his car and the obstacle and therefore he can either get himself or others. The damage is done on the car too. These increase the loss both of lives and property. The system designed in this project takes all the points into consideration and accordingly works in the real time. It employs the use of one of the most powerful MCU available in the market known as ‘Arduino Uno R3’ built around ATMEGA328P. It is cheap and easy to use. No installation cost needed, any person can install himself. In this project it is used in the 8 bit mode, shall put 10 bit ADC in the improved version because it offers 2¹⁰ = 1024 different analog levels. This improves the precision of the measurement.

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