Car Reverse Parking Sensor Circuit

Last Updated on March 16, 2024

It is somehow difficult to parking vehicles or taking reverse in tiny space, more important without damaging the vehicle parts. Here is a very helpful and effective solution given as a prototype.

The ultrasonic sensor Ranging module HC-SR04, Arduino nano board and a buzzer used in this design, by interfacing these elements we can built car reverse parking sensor circuit. This circuit works effectively over all obstacles and gives sensing range of 2cm to 400cm. The HC-SR04 requires only 5V and has minimum functional terminals.

Arduino Car parking Sensor Circuit

Circuit Diagram

Construction and Working

Car Reverse parking sensor circuit can be easily built with buzzer, Arduino nano and ultrasonic sensor HC-SR04 elements, here the HC-SR04 has two modules includes ultrasonic transmitter, receiver and inbuilt control circuit, this sensor sends eight 40KHz signal and detect whether there is a pulse signal back. If any signal back presents this sensor gives high level out.

Connect +5V supply from arduino nano board to +Vcc of ultrasonic sensor, connect Gnd to Gnd of ultrasonic sensor, after that connect trig pin to D8 and Echo pin to D9 of Arduino nano. As per the circuit and arduino code connect buzzer to D2 and Gnd. After uploading the Arduino sketch use separate 9V battery to power the arduino board through Vin pin.

Arduino Code for car reverse parking sensor circuit

This code built to detect the obstacles under 100cm range and you can vary this range upto 400cm depends on you need.


HC-SR04 Ping distance sensor
VCC to arduino 5v GND to arduino GND
Echo to Arduino pin 9 Trig to Arduino pin 8
Buzzer +ve to Arduino pin 2 and GND to GND
Original code sourced from
Some code and wiring inspired by

#define trigPin 8
#define echoPin 9
#define Buzzer 2

void setup() {
Serial.begin (9600);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
pinMode(Buzzer, OUTPUT);


void loop() {

digitalWrite(trigPin, LOW);
digitalWrite(trigPin, HIGH);
digitalWrite(trigPin, LOW);

duration = pulseIn(echoPin, HIGH);

distance = (duration/2) / 29.1;

if (distance < 100)
digitalWrite(Buzzer,HIGH); //less than 100cm then buzzer will produce beep sound

else {

if (distance >= 300 || distance <= 0)
Serial.println("Out of range");
else {
Serial.println(" cm");


Built the circuit and upload the sketch and then provide separate 9V battery to the Vin pin of Arduino nano then enclose all the elements with suitable plastic case and make open to the ultrasonic sensor modules and buzzer. Attach the plastic case in center part of vehicle.

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