What wakes up my computer?

[Asu]

I have a nice big imac, of course with a bunch of stuff. It suffers from middle insomnia, i.e. frequent awakening from sleep for reasons I would like to fond out so i can stop it. It goes to sleep all right, but I repeatedly find it awake, its screen blaring in the night. I have turned off "wake up for network access" but to no avail. Is there a way to find out which app or process awakens my computer? It has a Time machine drive attached but it can awaken several times in an hour so it is out as a likely cause. Any suggestions?

 

[Fishrrman]

"I repeatedly find it awake, its screen blaring in the night. I have turned off "wake up for network access" but to no avail.
Any suggestions?"

Yep.
Shut it down at night -- all the way off.

If you do this, it will not bother you -- 100% guaranteed!

 

[DeltaMac]

You should be able to find out what app or process wakes up your Mac.
That should be an event that will be recorded in your logs, and you can read the logs in your Console app.
The System.log will have that listed by time and date. Just look for entries after you last put your iMac to sleep.

 

[chown33]

1. Setup the Energy Saver in System Preferences to sleep after 5 minutes of inactivity.

2. Disconnect all USB devices: mouse, trackpad, keyboard, hubs, everything.

3. If the machine wakes up, then you know it's not a USB device triggering the wakeup, and you can look at processes, network, etc.

4. Conversely, if the machine stays asleep, then you know it's one of the USB devices. At that point, leave only one of them plugged in overnight. If it wakes up, then that's the device triggering the wakeup.