is there way that if user have any activity in 30 minutes, that user logout automatically. I use Ion_auth authentication in Codeigniter.
check the file system/cms/config.php and set the option $config['sess_expiration'] to the value you'd like to have (in seconds, so 30 minutes would be 1800 seconds).
Keep in mind that this won't immediately throw your user out of the session, but he will have to relog the next time he'll request something that utilises the session (e. g. a password protected page).