Hey there!

This car can be made easily by Newbies. Almost all the instructables had some or the other glitch due to which i made an easy method(also the cheapest i guess). One can easily control the car with an app via bluetooth.

it is a really fun weekend project for arduino/electronic enthusiasts.

Step 1: Materials Required

Here is the list of items required for making the car.

Bluetooth module "HC-05"
Adafruit motor Shield
Arduino Uno
Some jumper cables
A Power Source ( I used a Li-ion battery)
4 Wheels(I used 10 cm wheels)
4 Motors (preferably geared)
Some aluminium sheets or L shaped clamps for holding the motors
And other tools...

Step 2: Connections

Stack the Adafruit motor shield on top of arduino uno.
Now connect the Gear motors to M1,M2,M3,M4 respectively.Here I have used M1 and M2 for Front right and Rear Right wheels and M3 and M4 are Rear Right and Front left respectively.
Connect an external power supply to the board from the “EXT_PWR” socket of the Adafruit Motor Shield. This can run the Arduino also. There is no need of separate battery for it connection. I recommend using 12.8v or 14v (cause the shield could handle both. But still I prefer 12v battery. It depends on the availability of the battery in the store…)
Connect the HC-05 module’s VCC to 5V on Arduino ; Gnd to Gnd; The RX of Hc-05 becomes TX of Arduino and TX of Hc-05 becomes RX of Arduino.This is important as messing this up will result in the HC-05 being unable to give commands from your phone to the car.

Step 3: Construction

I have used a 6mm wooden sheet which was lying around in the house.
After cutting the Aluminium Sheets into rectangles, cut it in a rectangular manner.Make a hole for the shaft of the motor to fit in.Then bend these to form an "L" shaped clamp.
Drill holes into the base and fix it.
Pass the motor's shaft through the hole and tighten it using the nut provided with it.
Cover the motors wire with a sleeve to prevent short circuiting.

Step 4: Code

After double checking all the connections plug in your Arduino.

Ensure your Arduino IDE and firmwares are up to date(if not then click here https://www.arduino.cc/en/main/software) Download the Adafruit Motor Sheild library if you havent (by clicking here https://github.com/adafruit/Adafruit-Motor-Shield-library/zipball/master)

Download the file and upload it to the board.There shouldn't be any problem in compiling as i have checked it with Arduino Mega also; but still if at all you find any mistakes or bugs in the Sketch please let me know.