This is very easy to make and cheap robot you can get all the component on amazon and the app and sketch from playstore

Step 1: Component Needed

1.) 2 DC Geared Motors +Wheels (Bought it from amazon Rs.190)

2.)Chasis (From Amazon Rs.115)

3.)L293D IC Based DC Motor Control Board ( Amazon Rs.100)

4.) Caster Wheel (Amazon Rs.85)

5.)Battery bank (As per your power requirement I used 11000Ah cause i want to play more)(From flipkart Rs 650)

6.)Arduino UNO Board( You can use any board .I used Arduino Uno ) (From Amazon Rs 450)

7.)HC 05 Bluetooth Module(Amazon Rs.190)

8.)Jumper Wires Soldering Iron

9.) Arduino Bluetooth Control App from playstore (Because it is free and the amker also provide link to download the sketch which will work with the app. I have also uploaded the sketch with this instructable,Its just a modified version of the original sketch

Step 2: Connection

1.)Connect motor and caster wheel with the chasis

2.)Solder the jumper wires with motor (just take care of the polarity)

3.)Connect the motors to the motor control board (you will recognize automatically when you see the board its easy)

4.)Make a USB connector to give main supply to the board (Just cut you spare USB cables ,take care of the polarity)

5.)Now connect Motor control Board to arduino Uno (Refer the Pic)

Arduino Board

A1 -- 4

A2 -- 5

B1 -- 6

B2 -- 7

VCC- 5V

GND- GND

You can use other pins also accordingly you have to change the Sketch

6.)Connect Bluetooth Modue HC 05 to Arduino (Refer the Pic) (Do these connection after uploding sketch only or the sketch will not upload)

HC 05 Arduino

TX RX

RX TX

VCC 3.3V

GND GND

Step 3: Sketch and Other Details

1.)Upload the sketch to the board

2.)Download arduino bluetooth control on your mobile

Now In the app

Device 1 ON Motor 1 FWD

Device 2 ON Motor 1 Backward

Device 3 ON Motor 2 Fwd

Device 4 ON Motor 2 Backward

So for Fwd Movement Device 1 and 3 ON Other OFF

For Backward Movement Device 2 and 4 ON Other OFF

Like wise left and right

This is the best free app i got on play store and since Am not an app developer i am just using it

you can search for more apps or can modify the sketch for better control

In the next Instructable i will tell you how to connect the robot to internet so that you can control it from anywhere (Thats why i haven't done much research on Bluetooth app and sketch)

Video for internet controlled robot controlled via website (Will upload the instructions shortly)