Access violation

[rhmargus]

I placed on form TMySQLDatabase1,MySQLDataset1,dbGrid1,Datasource1 & Button1, and I add

procedure TForm1.Button1Click(Sender: TObject);
var db:TDatabase;
begin
    TMySQLDatabase1.DatabaseName:='plate';
    TMySQLDatabase1.HostName:='192.168.0.254';
    TMySQLDatabase1.UserName:='admin';
    TMySQLDatabase1.Password:='nimad';
    Datasource1.DataSet:=MySQLDataset1;
    dbGrid1.DataSource:=Datasource1;
    db.Name:='plate';
    MySQLDataset1.DataBase:=db;
    MySQLDataset1.Active:=true;
    TMySQLDatabase1.Open;
end;

In the same control of TMySQLDatabase1.Params I add "SELECT * FROM login"
When i build and start application, after click on button the messagebox is:

         "Access violation" (No message in Message Window)

Where I was wrong ?????????????????????

p.s. MySQL is active,host is OK, uname & password is OK ...