I have a MacBook Pro 13″ and after I had upgraded to Yosemite the device does't go in sleep mode when I want it (anything is disconnected from the device). I went to energy power savings to change my settings but still doesn't work.
This is what terminal shows to me with pmset -g assertions command:
2015-01-29 12:02:35 +0100 Assertion status system-wide: BackgroundTask 0 ApplePushServiceTask 0 UserIsActive 1 PreventUserIdleDisplaySleep 0 PreventSystemSleep 0 ExternalMedia 0 PreventUserIdleSystemSleep 0 NetworkClientActive 0
Listed by owning process: pid 76(hidd): [0x0000de4e000908e3] 00:17:53 UserIsActive named: "com.apple.iohideventsystem.queue.tickle" Timeout will fire in 286 secs Action=TimeoutActionRelease No kernel assertions.