DIY Arduino Bluetooth OBD2 Car Diagnostics Dashboard

Are you fascinated by your car’s inner workings and eager to peek under the hood – digitally speaking? This project guides you through creating a simple yet effective car diagnostics display using an Arduino, a Bluetooth OBD2 adapter, and a small LCD screen. By tapping into your car’s On-Board Diagnostics (OBD2) system wirelessly, you can access real-time data, starting with something as fundamental as your engine’s coolant temperature. This is an excellent entry point into DIY car electronics and understanding your vehicle’s health.

Parts You’ll Need for Your Arduino OBD2 Project

To get started, gather these affordable components. You can find them easily online:

• ELM327 Bluetooth OBD2 Adapter: This is the key interface to your car’s OBD2 port. It translates the complex car protocols into something your Arduino can understand. Expect to pay around $5.
• Arduino Uno (or similar): The brains of the operation. The Arduino will process data from the OBD2 adapter and display it. An Arduino Uno can be found for about $5.
• HC-05 Bluetooth Module: Enables wireless communication between the ELM327 adapter and your Arduino. Cost is approximately $5.
• LCD I2C Display (16×2 recommended): Provides a clear visual output for your car’s data. These displays are also around $5.

These components create a budget-friendly setup for exploring your car’s data.

Wiring Up Your Arduino, Bluetooth, and LCD

Let’s connect the hardware. Proper wiring is crucial for the project to function correctly.

Arduino Uno Connections:

• HC-05 Bluetooth Module: Connect the HC-05’s TX pin to the Arduino’s RX pin and the HC-05’s RX pin to the Arduino’s TX pin. Remember to use a voltage divider on the Arduino’s TX line to the HC-05 RX pin as the HC-05 is 3.3V logic and Arduino is 5V. For simplicity, you can often get away with direct connection, but for robust setups, level shifting is recommended. Also connect the HC-05 VCC and GND to the Arduino’s 5V and GND respectively.
• LCD I2C Display: The I2C LCD simplifies wiring significantly. Connect the LCD’s SDA pin to the Arduino’s SDA (A4) pin and the SCL pin to the Arduino’s SCL (A5) pin. Power the LCD by connecting its VCC and GND pins to the Arduino’s 5V and GND.

Configuring the HC-05 Bluetooth Module for OBD2 Communication

The HC-05 module needs to be configured to communicate with the ELM327 Bluetooth OBD2 adapter. We’ll set it up as the master device to connect to the ELM327 (slave).

HC-05 Setup Steps:

1. Enter AT Command Mode: To configure the HC-05, you need to put it into AT command mode. Typically, this involves holding down a small button on the module while powering it up. The LED on the HC-05 should blink slowly (e.g., every 2 seconds) indicating AT mode.

2. Connect via Serial Monitor: Use the Arduino Serial Monitor or a similar serial communication tool. Set the baud rate to 38400 (or the baud rate specified for AT commands for your HC-05 module).

3. AT Command Configuration: Enter the following AT commands one by one, pressing Enter after each:

   • AT+RESET (Resets the module)
   • AT+ORGL (Restores to default settings – optional but good practice)
   • AT+ROLE=1 (Sets the HC-05 as the Master)
   • AT+CMODE=0 (Sets connection mode to connect to a specific address)
   • AT+BIND=1234,56,789c72 (Replace 1234,56,789c72 with your ELM327’s Bluetooth address. Find this address by scanning for Bluetooth devices with your phone or computer.)
   • AT+INIT (Initializes the Bluetooth module)
   • AT+PAIR=1234,56,789c72,20 (Pairs with the ELM327. Again, use your ELM327 address. ,20 sets a 20-second timeout for pairing)
   • AT+LINK=1234,56,789c72 (Establishes the Bluetooth link to the ELM327)

Important Note: Disconnect the HC-05 TX and RX pins from the Arduino when uploading new code to the Arduino to avoid communication conflicts.

Software and Libraries for Your Arduino OBD2 Reader

To control the LCD and communicate over I2C, you’ll need to include necessary libraries in your Arduino code.

Required Libraries:

• Wire.h: This library is essential for I2C communication and is usually included with the Arduino IDE. If not, you may need to install it through the Arduino Library Manager.
• LiquidCrystal_I2C.h: This library simplifies controlling I2C LCD displays. You’ll likely need to install this library via the Arduino Library Manager (Search for “LiquidCrystal_I2C by Francisco Malpartida”).

Basic LCD Initialization Code:

In your Arduino code, include the libraries and initialize the LCD. The I2C address ( 0x3F in the example) might vary depending on your LCD module. You can use an I2C scanner sketch to find the correct address if needed.

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x3F, 16, 2); // Adjust address if needed

void setup() {
  lcd.init();
  lcd.backlight();
  lcd.print("OBD2 Temp:");
}

void loop() {
  // ... (OBD2 data reading and display code will go here) ...
}

This setup provides the foundation for reading OBD2 data via Bluetooth and displaying it on your LCD. From here, you’ll need to write the Arduino code to communicate with the ELM327 adapter using OBD2 commands to request coolant temperature and display the received value on the LCD. This project offers a fantastic starting point for deeper exploration into car diagnostics and Arduino-based vehicle interfaces.