App closes on Activ. 3 when pressing one of the buttons and does not send the data to Arduino. You could help me, I'm new to Android Studio, thanks!

Activity 1 (This is where the list of linked devices is made)

package com.example.artur.micasav3;

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.Set;

public class DispositivosBT extends AppCompatActivity {

    //1)
    // depuracion de LOGCAT

    private static final String TAG = "DispositivosBT";

    //DECLARACION DE LIST VIEW
    ListView IdLista;
    // String que se enviara a la actividad principal; ,ain activity
    public static String EXTRA_DEVICE_ADDRES = "device_address";

    // Declaracion de campos
    private BluetoothAdapter mBtAdapter;
    private ArrayAdapter<String> mPairedDevicesArrayAdapter;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_dispositivos_bt);
    }

    @Override
    public void onResume() {
        super.onResume();
        VerificarEstadoBT();

        //Inicializa la array que contandra la lista de los dispositivos bluetooth vinculados

        mPairedDevicesArrayAdapter = new ArrayAdapter<String>(this, R.layout.nombre_dispositivos); //parte a modificar

        // Presenta los dispositivos vinculasdos en LastView
        IdLista = (ListView) findViewById(R.id.IdLista);
        IdLista.setAdapter(mPairedDevicesArrayAdapter);
        IdLista.setOnItemClickListener(mDeviceClickListener);

        //Obtiene el adaptador local Bluetooth adapter
        mBtAdapter = BluetoothAdapter.getDefaultAdapter();

        //Obtiene un conjunto de dsipositivos actualmente emparejados y los agrega a "pairedDevices"
        Set<BluetoothDevice> pairedDevices = mBtAdapter.getBondedDevices();

        //Adiciona un dispositivo previo emparejado al array
        if (pairedDevices.size() > 0) {
            for (BluetoothDevice device : pairedDevices) {
                mPairedDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());
            }
        }
    }

    // Configura un (on-click) para la lista

    private AdapterView.OnItemClickListener mDeviceClickListener = new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView av, View v, int arg2, long arg3) {

            //Obtener la direccion MAC del dispositivo, que son los ultimos 17 acaracteres en la...
            String info = ((TextView) v).getText().toString();
            String address = info.substring(info.length() - 17);

            //Realiza  un intetnt para iniciar la siguiente actividad
            //Mientras toma un EXTRA DEVICE ADDRESS  que es la direccion MAC

            Intent i = new Intent(DispositivosBT.this, MenuPrincipal.class); // Parte a modificar
            i.putExtra(EXTRA_DEVICE_ADDRES, address);
            startActivity(i);
        }
    };

    private void VerificarEstadoBT() {
        // Comprueba que el dispositivo tiene Bluetooth y esta encendido
        mBtAdapter = BluetoothAdapter.getDefaultAdapter();
        if (mBtAdapter == null) {
            Toast.makeText(getBaseContext(), "El dispositivo no soporta Bluetooth", Toast.LENGTH_SHORT).show();
        } else {
            if (mBtAdapter.isEnabled()) {
                Log.d(TAG, "...Bluetooth Activado...");
            } else {
                //Solicita al usuario que active el Bluetooth
                Intent eneableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(eneableBtIntent, 1);
            }
        }
    }
}

Activity 2 (It is the main menu, where by means of a button I enter another activity)

package com.example.artur.micasav3;

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.Toast;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.UUID;
import android.widget.ImageButton;

public class MenuPrincipal extends AppCompatActivity {

    private TextView BufferIn, IdPorcentaje1, IdPorcentaje2, IdPorcentaje3;
    ImageButton IdImageIluminacion;


    Handler bluetoothIn;
    final int handlerState = 0;
    private BluetoothAdapter btAdapter = null;
    private BluetoothSocket btSocket = null;
    private StringBuilder DataStringIN = new StringBuilder();
    private ConnectedThread MyConexionBT;
    //Identificador unico de servicio - SPP UUID
    private static final UUID BTMODULEUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
    // String para la direccion MAC
    private static String address = null;
//-------------------------------------------

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_menu_principal);

        IdImageIluminacion = (ImageButton) findViewById(R.id.IdImageIluminacion);
        IdImageIluminacion.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent i = new Intent(MenuPrincipal.this, Iluminacion.class);
                startActivity(i);
                setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
            }

        });


        bluetoothIn = new Handler() {
            public void handleMessage(android.os.Message msg) {
                if (msg.what == handlerState) {
                    String readMessage = (String) msg.obj;
                    DataStringIN.append(readMessage);

                    int endOfLineIndex = DataStringIN.indexOf("#");

                    if (endOfLineIndex > 0) {
                        String dataInPrint = DataStringIN.substring(0, endOfLineIndex);
                        BufferIn.setText("Dato: " + dataInPrint);  //parte a modificar
                        DataStringIN.delete(0, DataStringIN.length());
                    }
                }
            }
        };

        btAdapter = BluetoothAdapter.getDefaultAdapter(); // get Bluetooth adapter
        VerificarEstadoBT();

    }

    private BluetoothSocket createBluetoothSocket(BluetoothDevice device) throws IOException {
        //crea un conexion de salida segura para el dispositivo
        //usando el servicio UUID
        return device.createRfcommSocketToServiceRecord(BTMODULEUUID);
    }

    @Override
    public void onResume() {
        super.onResume();
        //Consigue la direccion MAC desde DeviceListActivity via intent
        Intent intent = getIntent();
        //Consigue la direccion MAC desde DeviceListActivity via EXTRA
        address = intent.getStringExtra(DispositivosBT.EXTRA_DEVICE_ADDRES);
        //Setea la direccion MAC
        BluetoothDevice device = btAdapter.getRemoteDevice(address);

        try {
            btSocket = createBluetoothSocket(device);
        } catch (IOException e) {
            Toast.makeText(getBaseContext(), "La creación del Socket fallo", Toast.LENGTH_LONG).show();
        }
        // Establece la conexión con el socket Bluetooth.
        try {
            btSocket.connect();
        } catch (IOException e) {
            try {
                btSocket.close();
            } catch (IOException e2) {
            }
        }
        MyConexionBT = new ConnectedThread(btSocket);
        MyConexionBT.start();
    }

    @Override
    public void onPause() {
        super.onPause();
        try { // Cuando se sale de la aplicación esta parte permite
            // que no se deje abierto el socket
            btSocket.close();
        } catch (IOException e2) {
        }
    }


    //Comprueba que el dispositivo Bluetooth Bluetooth está disponible y solicita que se active si está desactivado
    private void VerificarEstadoBT() {

        if (btAdapter == null) {
            Toast.makeText(getBaseContext(), "El dispositivo no soporta bluetooth", Toast.LENGTH_LONG).show();
        } else {
            if (btAdapter.isEnabled()) {
            } else {
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(enableBtIntent, 1);
            }
        }
    }

    //Crea la clase que permite crear el evento de conexion
    public class ConnectedThread extends Thread {
        private final InputStream mmInStream;
        private final OutputStream mmOutStream;

        public ConnectedThread(BluetoothSocket socket) {
            InputStream tmpIn = null;
            OutputStream tmpOut = null;
            try {
                tmpIn = socket.getInputStream();
                tmpOut = socket.getOutputStream();
            } catch (IOException e) {
            }
            mmInStream = tmpIn;
            mmOutStream = tmpOut;
        }

        public void run() {
            byte[] buffer = new byte[256];
            int bytes;


            // Se mantiene en modo escucha para determinar el ingreso de datos
            while (true) {
                try {
                    bytes = mmInStream.read(buffer);
                    String readMessage = new String(buffer, 0, bytes);
                    // Envia los datos obtenidos hacia el evento via handler
                    bluetoothIn.obtainMessage(handlerState, bytes, -1, readMessage).sendToTarget();
                } catch (IOException e) {
                    break;
                }
            }
        }

        //Envio de trama
        public void write(String input) {
            try {
                mmOutStream.write(input.getBytes());
            } catch (IOException e) {
                //si no es posible enviar datos se cierra la conexión
                Toast.makeText(getBaseContext(), "La Conexión fallo", Toast.LENGTH_LONG).show();
                finish();
            }
        }

    }

}

Activity 3 (It's where I have 2 relays and pressing any button turns on arduino)

package com.example.artur.micasav3;

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.os.Handler;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.Toast;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.UUID;


public class Iluminacion extends AppCompatActivity {

    private TextView BufferIn;                    
    Button rele1, rele2;                                     


    Handler bluetoothIn;
    final int handlerState = 0;
    private BluetoothAdapter btAdapter = null;
    private BluetoothSocket btSocket = null;
    private StringBuilder DataStringIN = new StringBuilder();
    private ConnectedThread MyConexionBT;
    //Identificador unico de servicio - SPP UUID
    private static final UUID BTMODULEUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
    // String para la direccion MAC
    private static String address = null;
//-------------------------------------------

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_iluminacion);

        /////
        ActionBar actionBar = getSupportActionBar();
        actionBar.setDisplayHomeAsUpEnabled(true);
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        /////

        rele1 = (Button) findViewById(R.id.IdTodoOn);
        rele2 = (Button) findViewById(R.id.IdTodoOff);
        BufferIn = (TextView) findViewById(R.id.IdBufferIn);


        bluetoothIn = new Handler() {
            public void handleMessage(android.os.Message msg) {
                if (msg.what == handlerState) {
                    String readMessage = (String) msg.obj;
                    DataStringIN.append(readMessage);

                    int endOfLineIndex = DataStringIN.indexOf("#");

                    if (endOfLineIndex > 0) {
                        String dataInPrint = DataStringIN.substring(0, endOfLineIndex);
                        BufferIn.setText("Dato: " + dataInPrint);
                        DataStringIN.delete(0, DataStringIN.length());
                    }
                }
            }
        };

        btAdapter = BluetoothAdapter.getDefaultAdapter(); // get Bluetooth adapter
        VerificarEstadoBT();

        ////////ENCENDER O APAGAR TODOO////
        rele1.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                MyConexionBT.write("A");
            }
        });

        rele2.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                MyConexionBT.write("a");

            }
        });

    }

    private BluetoothSocket createBluetoothSocket(BluetoothDevice device) throws IOException {
        //crea un conexion de salida segura para el dispositivo
        //usando el servicio UUID
        return device.createRfcommSocketToServiceRecord(BTMODULEUUID);
    }

    @Override
    public void onPause() {
        super.onPause();
        try { // Cuando se sale de la aplicación esta parte permite
            // que no se deje abierto el socket
            btSocket.close();
        } catch (IOException e2) {
        }
    }


    //Comprueba que el dispositivo Bluetooth está disponible y solicita que se active si está desactivado
    private void VerificarEstadoBT() {

        if (btAdapter == null) {
            Toast.makeText(getBaseContext(), "El dispositivo no soporta bluetooth", Toast.LENGTH_LONG).show();
        } else {
            if (btAdapter.isEnabled()) {
            } else {
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(enableBtIntent, 1);
            }
        }
    }

    //Crea la clase que permite crear el evento de conexion
    public class ConnectedThread extends Thread {
        private final InputStream mmInStream;
        private final OutputStream mmOutStream;

        public ConnectedThread(BluetoothSocket socket) {
            InputStream tmpIn = null;
            OutputStream tmpOut = null;
            try {
                tmpIn = socket.getInputStream();
                tmpOut = socket.getOutputStream();
            } catch (IOException e) {
            }
            mmInStream = tmpIn;
            mmOutStream = tmpOut;
        }

        public void run() {
            byte[] buffer = new byte[256];
            int bytes;


            // Se mantiene en modo escucha para determinar el ingreso de datos
            while (true) {
                try {
                    bytes = mmInStream.read(buffer);
                    String readMessage = new String(buffer, 0, bytes);
                    // Envia los datos obtenidos hacia el evento via handler
                    bluetoothIn.obtainMessage(handlerState, bytes, -1, readMessage).sendToTarget();
                } catch (IOException e) {
                    break;
                }
            }
        }

        //Envio de trama
        public void write(String input) {
            try {
                mmOutStream.write(input.getBytes());
            } catch (IOException e) {
                //si no es posible enviar datos se cierra la conexión
                Toast.makeText(getBaseContext(), "La Conexión fallo", Toast.LENGTH_LONG).show();
                finish();
            }
        }

    }
}