yunlzheng/angular-knob — pull request #16 by DexterMorg4n (2014-10-08 13:34:43+00:00)
Title: change scope.knob to var knob.

scope.knob = scope.$eval(attrs.knobData);
to
var knob = scope.$eval(attrs.knobData);

If you name the data variable $scope.knob in the main scope than the directive will overwrite it and $watch will not function.
An internal variable is better