To make a smartphone-controlled Arduino Car using a Bluetooth module.
The Robot Car Kit can be purchased from eBay and other online websites for less than $25.
The L293d is necessary for sending voltage to the four motors, the Arduino is incapable of providing enough current for our motors by itself.
For the phone to control the robot we will need an HC-06 Bluetooth module onboard our robot.
Use a battery pack and the output voltage of your battery(s) to be between 6 and 12 volts.