Ok i got the point.It's not that easy as i thought
For anyone that still haven't got the point and don't like "...very complicated diagrams..."
A much simpler explanation, using an array of 100 cameras and 100 cheap power adapters.
Lets say each camera uses 3 watts thats 300 watts supplied from the 100 cheap power adapters.
Starting with the case where array of 100 cameras is powered from the original canon battery's:-
* There is NO External (sneaky) available paths for the current's to flow through.
* The original canon battery has very low internal resistance.
* The Canon Battery management system works even when internal resistance rises.
* There are FCC compliance rules regarding (RF) escaped energy.
In the case of the 300 watts supplied from the 100 cheap power adapters.
* The Canon Battery management system works with cheap power adapters.
* The cheap power adapters probably have much higher internal resistance.
* There are multiple External (sneaky) available paths for the currents to flow through.
* Some Canon P&S cameras have a 1/4-20 Metal tripod mount.
* Via the USB-B cable connectors.
* Via the 100 cheap power adapters power cables.
* Via the Optional Battery third terminal Sync.
* Via other sneaky Common mode current paths, i.e. Restive, Magnetic, Capacitive Coupling.
* The sneak currents or escaped energy Causes very random effects as per prior posts.
* The 100 cheap power adapters are also a SOURCE of sneak currents.
Only a very small percentage of the original 300 watts will, in practice, will directly affect the Sync.
So let's say its 0.1% this is still very significant amount of sneak currents going through your
"Rats Nest" wiring which could have 100 or even 1000 times more "Electrical Length" than
a simple prototype rig with only a couple of cameras .
So the overall project aim is just to try to have some sort of control over the sneak currents.
And have some sort of control (plan) over the Common Sync wiring before construction starts.
Edit #1 attached Multi-Camera_Array_Concept [+Rats].png
This is the case when the Sync is hard wired to each camera in the array.
So the aim is to dissapate the energy in the Parallel Sync Pulse in a resistor at the
far end of the USB-2 +5 Volt Sync Wire. [when using USB-2 Hot-Plug]
* USB-2 Hot-Plug Parallel Sync Pulse will be faster, so there is less USB-Jitter effect.
* Less sneak currents or escaped energy will be picked up via the common mode noise.
Note That this applies also to Opto-Couplers. They have another issue to consider.
"Miller Effect", this is also helped by individual termination resistors, but at the cost of
sensitivity of the Opto-Couplers. seehttp://en.wikipedia.org/wiki/Miller_effect
This one in series of post's in regard to Multi-Camera Arrays is also about what physical/scaling
effects that might/may become important a CHDK Multi-Camera Array Constructor.
I regard to USB-2 there is probably over a billion USB-2 devises in use, i.e. a well proven technology.
I regard to USB-2 Hot-Plug CHDK Remote Switching [Non-array] devises in use, may be well over
10,000 i.e. another well proven technology.
I regard to USB-2 Hot-Plug CHDK Remote Switching, for Large Camera Arrays, devises in use, might
be about 20. i.e. an emerging technology.
Edit #3 see Reply #59 by W-W ... [Fixed some stuff]
"...nobody has ever made it work...."
The Post is about "trying to make it work better" as you increase the number of cameras in the array.
Also "...describing here is a simple exercise in Ohm's law..."
The Post is really about "Reactance" effects as you increase the size and number of cameras in the array.
[ i.e. Restive, Magnetic, Capacitive Coupling.] http://en.wikipedia.org/wiki/Electrical_reactance