$db is undefined : error database

[eluser]Unknown[/eluser]
I have an error with my database config, CI do not recognize $db.
Someone what is the problem ?

this is the error :


A PHP Error was encountered

Severity: Notice

Message: Undefined property: Product::$db

Filename: core/Model.php

Line Number: 51

Fatal error: Call to a member function query() on a non-object in C:\wamp\www\MyApplication\application\models\MyModel.php on line 26