How to trigger the haptic pulse in the htc vive controller through script

I have recently started developing for htc vive. I am unable to figure out how to trigger the haptic pulse in the htc vive controller through script. I am using steamvr plugin for unity. I am using Unity 5.3.3

I have figured this now and got it working:

SteamVR_Controller.Input ((int)trackedObj.index).TriggerHapticPulse(500);

The parameter is the duration (in milliseconds) to vibrate the pad . This actually convert to the strength of pule you feel on controller. I have tried few values between 100 to 2000ms and settled for 500ms.

does this go on the controller?