Fully Recycled Home Assistant Bluetooth Smart Car (3d Printed) With Wifi

please keep in mind my text is original but fine-tuned by AI

A little about this project PLEASE READ

Being a 13-year-old stuck at home with nothing to do but homework, I wanted to challenge myself and see what I could build on my own, only rule -- it had to be made from recycled parts I can find around the house with no outside help. This project took three weeks, a lot of hot glue, and even more determination. I went into it knowing I might fail but also knowing I’d learn something no matter what. This project is mostly designed for whatever your wildest dreams may be, for me it was communicating with family members using the onboard OLED display and the app. I still haven’t tested traction on every surface yet, but oddly enough, my tablecloth worked the best so far. It has a .96'' oled display and it shows a QR code to a website with the instructions on how to work the car (car.arihantnag.com). The controls turned out a bit janky, but I’m honestly proud—because every single part of this build was fun, meaningful, and full of little lessons. And no matter how many times the wheels fall off, I’ll keep finding a way to put them back on. I hope you will too. That’s really why I do all this: to get better, to learn, and to enjoy the process. If you try making this project yourself, get ready for a roller coaster—problems, mistakes, moments of frustration—but also the joy of surprising yourself and the excitement of creating something real. Most importantly, be ready to HAVE FUN! So here it is:A Bluetooth-controlled Arduino R4 smart car featuring multiple sensors, servos, and an OLED display. It can be driven from a mobile app, shows status info on-screen, includes safety features like obstacle stopping, and has fully customizable controls and behaviors (well sometimes it has a mind of its own).

Supplies

here is an AI GENERATED IMAGE of the main components

Arduino UNO R4 Wi-Fi (main brain)

HC-05 / HC-06 Bluetooth module(the classic Arduino Bluetooth controller-compatible one)

L298N motor driver(or similar dual H-bridge driver) ONLY IF YOU WANT TO USE TT MOTORS

4x SG92R continuous rotation servos

OLED Display (SSD1306) – 128×64

Servos(for attachments or steering, depending on your build)

Ultrasonic Sensor HC-SR01 / HC-SR04(used for auto-stop at 6 inches)

2 rechargeable 9v batteries for power

Step 1: Your Frame

Pick a strong recycled material (old toy car base, plastic board, scrap wood, etc.).
Cut it to roughly 20×12 cm.
Mark where the motors, Arduino R4, batteries, and sensors will go.
Mount the 4 SG92R continuous rotation servos—two on each side.
Attach wheels and make sure they spin freely.

if you want to 3d print the chassis, use PLA or recycled bottle filament but the best would be ASA, PETG, CF.

Step 2:

Battery 1 → Arduino R4

Battery + → VIN

Battery – → GND

Battery 2 → Servo Power

Battery + → servo power rail (+5–6V)

Battery – → servo ground rail (GND)

IMPORTANT:

Connect both grounds together

Servo GND rail → Arduino GND

(So signals work correctly.)

SERVOS (4× SG92R CONTINUOUS ROTATION)

Each servo has:

Brown → GND

Red → +5–6V (servo battery)

Orange → Signal pin

Servo signal pins:

Front Left Motor → D5

Back Left Motor → D6

Front Right Motor → D9

Back Right Motor → D10

HC-05 / HC-06 BLUETOOTH MODULE

(VCC = 5V, but data is 3.3V tolerant enough for HC-05)

HC-05 VCC → 5V

HC-05 GND → GND

HC-05 TX → Arduino R4 RX (Pin 0)

HC-05 RX → Arduino R4 TX (Pin 1)

You must disconnect TX/RX while uploading code.

OLED DISPLAY (SSD1306, I2C)

Using I2C pins on the R4:

OLED VCC → 3.3V

OLED GND → GND

OLED SDA → SDA (Pin A4)

OLED SCL → SCL (Pin A5)

ULTRASONIC SENSOR (HC-SR01 / HC-SR04)

VCC → 5V

GND → GND

TRIG → D6(or your chosen pin)

ECHO → D5(or your chosen pin)

(You said Echo = GPIO 5 and Trig = GPIO 6, so I matched that.)

FULL WIRING SUMMARY (Quick List)

Power

Arduino VIN → Battery 1 +

Arduino GND → Battery 1 –

Servo + rail → Battery 2 +

Servo GND rail → Battery 2 –

Servo GND rail → Arduino GND

Servos

ServoPinNotes

Front Left

CR servo

Back Left

CR servo

Front Right

CR servo

Back Right

D10

CR servo

(Each has brown=GND, red=5V, orange=signal)

Step 3:

code (you can also get it at car.arihantnag.com)

#include <Servo.h>

#include <Wire.h>

#include <Adafruit_GFX.h>

#include <Adafruit_SSD1306.h>

// ----------------------

// OLED SETUP

// ----------------------

#define SCREEN_WIDTH 128

#define SCREEN_HEIGHT 64

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

// ----------------------

// SERVO PINS

// ----------------------

Servo FL; // Front Left

Servo BL; // Back Left

Servo FR; // Front Right

Servo BR; // Back Right

#define FL_PIN 5

#define BL_PIN 6

#define FR_PIN 9

#define BR_PIN 10

// CR SERVO SPEED SETTINGS

int forwardSpeed = 1700;

int backwardSpeed = 1300;

int stopSpeed = 1500;

// ----------------------

// HC-SR04 PINS

// ----------------------

#define TRIG_PIN 6

#define ECHO_PIN 5

// ----------------------

// BLUETOOTH

// ----------------------

#define BT_SERIAL Serial1 // works on UNO R4 with HC-05 TX->0, RX->1

// ----------------------

// FUNCTIONS

// ----------------------

void stopAll() {

FL.writeMicroseconds(stopSpeed);

BL.writeMicroseconds(stopSpeed);

FR.writeMicroseconds(stopSpeed);

BR.writeMicroseconds(stopSpeed);

}

void forward() {

FL.writeMicroseconds(forwardSpeed);

BL.writeMicroseconds(forwardSpeed);

FR.writeMicroseconds(forwardSpeed);

BR.writeMicroseconds(forwardSpeed);

}

void backward() {

FL.writeMicroseconds(backwardSpeed);

BL.writeMicroseconds(backwardSpeed);

FR.writeMicroseconds(backwardSpeed);

BR.writeMicroseconds(backwardSpeed);

}

void leftTurn() {

FL.writeMicroseconds(backwardSpeed);

BL.writeMicroseconds(backwardSpeed);

FR.writeMicroseconds(forwardSpeed);

BR.writeMicroseconds(forwardSpeed);

}

void rightTurn() {

FL.writeMicroseconds(forwardSpeed);

BL.writeMicroseconds(forwardSpeed);

FR.writeMicroseconds(backwardSpeed);

BR.writeMicroseconds(backwardSpeed);

}

// ----------------------

// DISTANCE CHECK

// ----------------------

long getDistance() {

digitalWrite(TRIG_PIN, LOW);

delayMicroseconds(2);

digitalWrite(TRIG_PIN, HIGH);

delayMicroseconds(10);

digitalWrite(TRIG_PIN, LOW);

long duration = pulseIn(ECHO_PIN, HIGH);

long distance = duration * 0.0133 / 2; // convert to cm

return distance;

}

// ----------------------

// OLED TEXT

// ----------------------

void showText(String msg) {

display.clearDisplay();

display.setTextSize(2);

display.setTextColor(SSD1306_WHITE);

display.setCursor(0, 20);

display.println(msg);

display.display();

}

// ----------------------

// SETUP

// ----------------------

void setup() {

Serial.begin(9600);

BT_SERIAL.begin(9600);

// OLED

if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {

while (1);

}

display.clearDisplay();

display.display();

// Servos

FL.attach(FL_PIN);

BL.attach(BL_PIN);

FR.attach(FR_PIN);

BR.attach(BR_PIN);

stopAll();

// Ultrasonic

pinMode(TRIG_PIN, OUTPUT);

pinMode(ECHO_PIN, INPUT);

showText("READY");

}

// ----------------------

// LOOP

// ----------------------

void loop() {

long distance = getDistance();

// Auto-stop at 6 inches (~15cm)

if (distance > 0 && distance < 15) {

stopAll();

showText("STOP (OBSTACLE)");

delay(200);

return;

}

if (BT_SERIAL.available()) {

char cmd = BT_SERIAL.read();

Serial.println(cmd);

switch (cmd) {

case 'F':

showText("FORWARD");

forward();

break;

case 'B':

showText("BACKWARD");

backward();

break;

case 'L':

showText("LEFT");

leftTurn();

break;

case 'R':

showText("RIGHT");

rightTurn();

break;

case 'S':

default:

showText("STOP");

stopAll();

break;

}

Step 4:

Test motors and servos without Bluetooth first

Upload a simple sketch that rotates motors or servos to ensure correct wiring.

Connect via Bluetooth

Open the app, ensure the car responds to button presses.

Drive in a safe area

Avoid walls and obstacles.
If you have an ultrasonic sensor, make sure the code stops the car ~6 inches from obstacles.

Monitor feedback

If using OLED/Serial Monitor, check motor/servo angles or distance readings.

CommandFunctionOLED Shows

Move Forward

Turn Left

Turn Right

Backward

BACK

Stop / Idle

IDLE

Open servo (0°)

OPEN

Close servo (180°)

Step 5:

get wheels here or just download:🛞 Wheel for SG90 Servo・Free STL File for ・Cults

frame/chassis ⬇

Step 6:

YOUR DONE! keep in mind that the material for the wheels can make it better on the surface you drive on. With your Arduino R4 Bluetooth car fully assembled, programmed, and tested, you now have a fully functional, controllable robotic vehicle at your fingertips. From precise motor control to servo-driven mechanisms, and optional sensors for obstacle detection, this car is not just a project—it’s a platform for experimentation and if you had nearly as much fun as me building it, then give yourself a pat on the back, you just did the work of a 13-year-old.

DJI_20251206112526_0151_D.mp4
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Introduction: Fully Recycled Home Assistant Bluetooth Smart Car (3d Printed) With Wifi

Attachments

Supplies

Step 1: Your Frame

Step 2:

Battery 1 → Arduino R4

Battery 2 → Servo Power

SERVOS (4× SG92R CONTINUOUS ROTATION)

Each servo has:

Servo signal pins:

HC-05 / HC-06 BLUETOOTH MODULE

OLED DISPLAY (SSD1306, I2C)

ULTRASONIC SENSOR (HC-SR01 / HC-SR04)

FULL WIRING SUMMARY (Quick List)

Power

Servos

Step 3:

Step 4:

Step 5:

Attachments

Step 6:

Attachments