In this article you will read about the construction of a car controlled by your android phone. It might sound a bit complicated but the hard part is the android part, thankfully Andi.co with the app "Arduino Bluetooth RC Car" has made out life easier, all we have to do is download the app and connect to the bluetooth module once we have programmed the arduino board, and make our electronic connections. Following the schematic, we'll see that we connect a 9v battery to our motor controller which is a L298N Bridge, basically it gets orders from our arduino and does all the "heavy duty work" since arduino can't provide directly enough power. My L298N board had a voltage regulator, so the Battery clips were connected to the pins "Vin" and "Ground", also I connected my battery to 'Vin" and "Ground" of arduino. In the schematic you will see the rest of the connections of the L298N which afford the connections betweens motors, and the arduino pins. Finally there is the bluetooth module which has 4 connections and they are 5V,Ground, Rx,Tx. As we know from the previous project Rx of Arduino connects to Tx of Bluetooth module and Tx of Arduino connects through a voltage divider to Rx of the Bluetooth Module. We can connect any type of resistors as long we can provide 3.3 volts to our pins. In my example I use 1K and 2K. The rule of the voltage divider is this : Vout = [Rdown / (Rdown + Rup)] x Vin. So : [2K / (2K+1K)] x 5V = 0.6666 x 5V = 3.3 Volts. Lastly one crucial reminding is : DON'T CONNECT THE BLUETOOTH WHEN YOU UPLOAD THE SKETCH TO ARDUINO, or else you will have some conflicts and you will scratch your head for hours!