Here is the non-derail setup recommended by Z-Stuff. The power is 12 VAC, direct from the accessory posts on your transformer. You need 12 VAC minimum. The diodes prevent back current going to the led's on your controller. You do not need the DZ-1008 relay.
One suggestion - see where the switch approach rails are cut, do NOT cut the rails on the switch. Cut about a 3" section of rail before this, on the rail leading up to the switch. Doing this prevents possible damage to the switch rails.
Bruce