Bluetooth xm-15b & Ln298

[sebi6576]

Hello,

I have a problem while connecting arduino UNO with the bluetooth module Xm-15b and the driver LN298.
I am making a 2 wheels robot controlled by bluetooth.
The problem is that when i am connected to the computer port ("COM4"), it works; but if i use the 9v battery instead of the computer, although everything turn on, the connection with my cellphone (using BluetoothSerialController.apk) doesnt work when i reconnect it to the module.

the code is the following:

int in1 = 7;
int in2 = 6;
int in3 = 5;
int in4 = 4;


void setup()
{
  Serial.begin(9600);
  pinMode (in1,OUTPUT);
  pinMode (in2,OUTPUT);
  pinMode (in3,OUTPUT);
  pinMode (in4,OUTPUT);
}

void loop()
{
  if (Serial.available()>0)
  {
    char nodato  = Serial.read();
    char dato = char (nodato);
    if (dato == '0')
    {
      digitalWrite (in1,LOW);
      digitalWrite (in2,HIGH);
      digitalWrite (in3,HIGH);
      digitalWrite (in1,LOW);
    }
    if (dato == '1')
    {
      digitalWrite (in1,HIGH);
      digitalWrite (in2,LOW);
      digitalWrite (in3,HIGH);
      digitalWrite (in1,LOW);
    }
    if (dato == '2')
    {
      digitalWrite (in1,HIGH);
      digitalWrite (in2,LOW);
      digitalWrite (in3,HIGH);
      digitalWrite (in1,LOW);
    }
    if (dato == '3')
    {
      digitalWrite (in1,HIGH);
      digitalWrite (in2,LOW);
      digitalWrite (in3,LOW);
      digitalWrite (in1,HIGH);
    }
    if (dato == '4')
    {
      digitalWrite (in1,LOW);
      digitalWrite (in2,LOW);
      digitalWrite (in3,LOW);
      digitalWrite (in1,LOW);
    }
  }
}


the connections are these:

xm-15b:
     

[pert]

The common 9 V battery can't supply enough current for a robot. You'll need to use a better power source. A decent quality/capacity (the cheap ones often lie outrageously about their capacity) USB power pack might be an easy solution, perhaps you already have one on hand.

[pert]

sebi6576 provided a bit more information in their cross post:

the connections are like these:

XM-15B:
    5v -> 5v arduino (using protoboard)
    gnd -> gnd arduino ("" "")
    rx -> tx arduino
    tx -> rx arduino

Ln298:
    +12v -> 5v arduino (using protoboard) //I use 12v, because the wheels dont move if i use +5v
     gnd - > gnd arduino (using protoboard)
     in1 -> pin 4 arduino
     in2 -> pin 5 arduino
     in3 -> pin 6 arduino
     in4 -> pin 7 arduino
     
#wheels are connected in each side of the ln298 driver, using 2 wires for wheel.