For others reading this who may, as I was, be unfamiliar with "LANC"....
It is a protocol(?) defined by Sony. Lots of good stuff, including Arduino code and hardware info at...http://controlyourcamera.blogspot.com/2011/02/arduino-controlled-video-recording-over.html
I think the reference above to "LANC line" means the connection from the Arduino to the poster's video camera, the line over which he/ she sends the commands to his camera.
As I understand the question, there's no problem with the "remote" aspects of the problem.
(Advice to poster: For now, replace the Xbee signal with a simple pushbutton connected to a spare input of your Arduino. When the system is working to turn on camera, etc, when you push the button, you can then substitute the code for "I saw button pressed" with "Xbee saw movement", and you are done. Develop in stages, getting each bit working separately.)
ANYWAY... back to the question...
I need the LANC line to connect to ground for >140 ms to power up my camera.
Are you sure? That didn't make any sense to me, until at the page cited I saw...
It is a two-way serial open collector 9600 baud protocol with inverted logic.
After sending those two bytes the LANC signal must be be left alone and put back to LOW i.e +5V.
.. at which point things began to make sense... but only because I've spent years banging my head against certain walls.
First, a quibble with what I quoted. I think the second sentence should read...
After sending those two bytes the LANC signal must be be left alone and put back to "zero" i.e +5V.
"Inverted logic" means that a low voltage stands for "1" and a high voltage stands for "0".
The "open collector" stuff means, I think, that you have a network... in this case a "network" of just two devices... but with the potential for more to be added... with two wires running between all the connected devices. One for ground. Boring, but necessary, and sometimes not mentioned for the sake of beginners, and the "signal" wire.
Somewhere, in this case at the video camera, something attempts to hold the signal at a high voltage... 5v, it would seem in this case. But that "holding high" isn't very "strong", and it is perfectly acceptable, indeed intended, that from time to time devices on the network, or even the device normally pulling the line high, will "short" it to zero volts... which will be "seen" by all devices on the network.
So, in this case, the Arduino is supposed to pull the line low for 140ms, the video camera is going to "see" this, and is designed to "do something" when that happens.
Setting an output low for 140ms is not hard. I suspect you, original poster, are already doing this properly. Just check, though... tweak your code to pull the line low for 800ms, and watch with a voltmeter to see the line DOES go low. If so, on to the next thing....
Are you sure about everything you said? You said you've turned the camera off. If it is "off off", it won't be looking and the LANC interface, won't be doing anything... including holding the signal line weakly high... and thus won't notice the 140ms short- to- ground that your Arduino is generating.