Hi Ajith,
Power is the problem here. I faced the same problem connecting multiple devices and arduino to 5VDC. As per
the Arduino UNO data sheet, You need to give (7 - 12) volts to arduino input in Vin pin, unless you give supply 5V through USB. Once you connect +12VDC to arduino and +5VDC to all motors, your system will work just fine.