DIY - Arduino Based Car Parking Assistant




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Hi Friends,

I am back again with another Arduino based home automation project. This time I am trying to make my partner's life easy by installing a collision avoidance system in the garage to help her park the car safely without hitting the garage wall.

So, in this video, I am going to use an ultrasonic sensor to calculate the car's distance from the garage wall and display it using green, yellow and red LEDs. The color of LEDs indicates whether to keep moving, slow down, stop or go back.

The total cost of the project is around $20 - $25.

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Step 1: ​Logic

The project has 3 phases

Phase 1: Waiting for the car In this phase the device keeps looking for a moving object within the sensors proximity. If an object enters the proximity then one of the three LEDs turns on based on how far the moving object is. If the object is way too close, then a noise is made to make the moving object aware of the distance.

Phase 2: No car in the garage If there is no object in the proximity then turn off all the LEDs.

Phase 3: The car has stopped moving (Parked in the right spot) If the object has stopped moving and is still in the proximity wait for 20 CPU cycles and then turn off the LEDs.

Step 2: Hardware Requirement

For this very simple project we need:

- A Perfboard

- An Arduino nano/uno (whatever is handy)

- A Red, Green and a Yellow LED (Light Emitting Diode)

- 3 x 220ohm resistor for the LEDs

- One HC-SRO4 Ultrasonic Sensor

- A Buzzer shield or A buzzer and a 100 ohm resistor

- A 220v AC to 5v DC Buck step-down module

- One Female Pin Header Strip

- An Ethernet cable

- Some connecting cables

- A USB cable to upload the code to the Arduino

- and general soldering equipments

Step 3: Assembly

Let start by connecting the LEDs to the board.

Connect the Red LED to pin D2, Yellow LED to D3 and the Green LED to D4 of the Arduino by putting in a 220ohm resistor between the Arduino board and the LEDs. Now lets connect the Buzzer to analogue pin A0. Next, connect the Trig pin of the Ultrasonic Sensor to D5 and the Echo pin to D6 of the Arduino. Once all the modules are connected to the Arduino board, its time for us to connect all the positive and negative pins together. Connect all the positive pins of the modules to the +5v supplied by the Buck Step-Down Module and the negative pins to the -ve terminal of the Module. That's it, we can now upload our sketch to the board.

In this assembly I am using 3 LEDs to display the distance, however you can replace the 3 LEDs with a RGB LED, or you can also use an array of LEDs like an audio level indicator to display the movement of the car.

Step 4: My Setup

OK now lets see what I have made.

I have installed the Arduino, buzzer, the ultrasonic sensor and the three 220 ohms resistors on one Perfboard. The 3 LEDs and the power module is installed on a second Perfboard. I will be covering the LEDs with a translucent cover to give it a nice look.

The 220v power supply will be connected to the screw terminal block. The base unit will then be connected to the LEDs and the power supply with an Ethernet cable.

Step 5: The Code

int trigPin = PD5; // Sensor Trip pin connected to Arduino pin D5

int echoPin = PD6; // Sensor Echo pin connected to Arduino pin D6

int redLED = PD2; // Red LED connected to pin D2

int yellowLED = PD3; // Yellow LED connected to pin D3

int greenLED = PD4; // Green LED connected to pin D4

int buzzer = A0; // Buzzer connected to Analogue pin A0

long TempDistance = 0; // A variable to store the temporary distance

int counter = 0; // Counter value to check if the object has stopped moving

void setup() {


pinMode(trigPin, OUTPUT);

pinMode(echoPin, INPUT);

pinMode(redLED, OUTPUT);

pinMode(greenLED, OUTPUT);

pinMode(yellowLED, OUTPUT);

pinMode(buzzer, OUTPUT);


void loop() {

long duration, Distance;

digitalWrite(trigPin, LOW);


digitalWrite(trigPin, HIGH);


digitalWrite(trigPin, LOW);

duration = pulseIn(echoPin, HIGH);

Distance = (duration/2) / 74; // Distance in Inches

if(counter < 20){ // Do the rest if the car is still moving

if (Distance > 200) { // Nothing in the garrage



if ((Distance > 55) && (Distance <= 200)) { // Turn on Green LED

digitalWrite(greenLED, HIGH);

digitalWrite(yellowLED, LOW);

digitalWrite(redLED, LOW);



if ((Distance > 15) && (Distance <= 55)) { // Turn on Yellow LED

digitalWrite(yellowLED, HIGH);

digitalWrite(redLED, LOW);




if (Distance <= 15) { // Turn on Red LED

digitalWrite(redLED, HIGH);


digitalWrite(yellowLED, LOW);



if (Distance < 8) { // Item is way to close - start the buzzer

tone(buzzer, 500);



if ((Distance == TempDistance) || ((Distance+1) == TempDistance) || ((Distance-1) == TempDistance)){

if(counter >= 20){ // Turn off the lights if the object hasn't moved for 20 cycles (no change in distance)

Serial.println("No movement detected, turning off the lights");


} else {



} else {

counter = 0; // Reset counter if there is a movement


TempDistance = Distance;


Serial.println(" inches");

Serial.print("Counter : ");

Serial.println(counter); delay(500); }

// Function to turn the LEDs off

void turnThemAllOff(){

digitalWrite(redLED, LOW);


digitalWrite(yellowLED, LOW);



Start the code by defining the constants and the global variables that will be used throughout the code.

Then define the pin modes in the setup section of the code.

Then create a function to turn off all the LEDs and the buzzer.

Now, calculate the "Distance" in inches by reading the values received from the Ultrasonic Sensor.

Then by checking the value of the "Distance" we will turn on and off the LEDs based on how far the object is. If the distance is greater than 200 then turn off all the LEDs and the buzzer as the object is out of range. Else if it is between 55 and 200 then turn on the green LED. If the object is between 15 and 55 then turn on the yellow LED, and if the object goes closer than 15 inches then turn on the red LED until it reaches 8 inches. When the distance becomes less than 8 start the buzzer along with the red LED.

Next bit of the code is to set the value of the counter based on the cars movement which then decides when to turn off the LEDs. It compares the value of "Distance" with the "TempDistance" and if the values are same (object hasn't moved) then increments the counter. If the object moves any-time during this process the counter is reset to 0. Finally the "TempDistance" is set to the value of "Distance".

Just before comparing the Distances we also need to check if the counter value has exceed 20. I am doing this to stop the below code from executing if the car is in a steady position.

Lastly we just need to add a small delay to our sketch to pause the code for a while.

Step 6: Quick Demo

So this is how I have installed the unit in my garage.

As I walk close to the sensor the light changes from green to yellow to red and ultimately the buzzer goes on when I am too close to the sensor. In my case I have installed the buzzer next to the Arduino however I will recommend you to install the buzzer along with the LEDs. If you want you can also flash the red LED when the buzzer goes on.

So now, my partner can park the car easily without making any assumptions. Doesn't matter how many times she fail her driving test she is not going to break my wall (even when she is drunk). Not that I am asking her to drive when she is drunk (just kidding).

Thanks again for watching this video! I hope it helps you. If you want to support me, you can subscribe to my channel and watch my other videos. Thanks, ca again in my next video.

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    14 Discussions


    Question 9 months ago on Step 1

    Hi! I have ordered the required items for this build, but I don't know where I can buy the correct 'A 220v AC to 5v DC Buck step-down module'. I live in Europe so my wall outlet is 230v. Can you help me? Thanks!

    1 answer

    Question 1 year ago on Step 6

    Thanks for the response. You used the right word when you said 'blindly" I'll let you know how I do.

    1 answer

    Question 1 year ago on Step 6

    I would love to do this but I have zero coding experience. Is there a way that I can do without coding knowledge? (And too dumb to learn how)

    2 answers

    Answer 1 year ago

    I have provided the full coding and the things you need to know to code and seti it up.

    You should be able to blindly follow the instructions to make one for your home.

    Let me know if you get stuck anywhere and I can give you a hand.

    Subscribe to my YouTube channel for more amazing home automation projects.


    Question 11 months ago

    J'ai réalisé le câblage à l'identique et téléversé le code, la led rouge s'allume en permanence et le buzzer sonne pendant 30 secondes environ puis tout s'arrête !
    J'ai essayé avec trois HC-SR04, vérifié les connexions.
    Avez-vous une idée ?

    1 answer

    Answer 11 months ago

    Can you please check the wiring again, looks lie something wrong with the wiring


    Question 1 year ago

    I am new to doing Ardunio projects, and this is actually pretty close to a project I had in mind. My question is, how did you use the ethernet cable? Are you using some sort of connector or are you stripping the shielding and connecting the wires yourself to where you want them to be?

    1 answer

    Answer 1 year ago

    Yes sure, why not.

    But then you will have this issue of detecting the object and displaying the status at the same time..

    As if you put both near the bumper area then you wont be able to see the lights, and if you put both on top then the sensor may not give you the right reading due to the sound waves getting bounced by the windscreen


    1 year ago