James [at Gentles] has previously reported [for a hundred cams]:
"There is a high chance that it doesn't have the drive to trigger this many"
I designed that in association with James.
He is referring to the drive capability of the tiny battery in SDM Pro switch.
Simply use an ordinary switch and three AA batteries, no problem.
The input resistance of each camera is tens of kohms so even 70 in parallel is still an appreciable resistance.
I was really suggesting use of the extender, this is the sort of application it is designed for.
- however, I want to use [if possible] an ambient light sensor to both switch the usb [and hubs] to 0V and that same sensor providing an input to the arduino controller [to control studio flash AND potentially the remote trigger shutters of multiple DSLR's].
Forget about the ambient light.
Normally, you pull the USB voltage low and wait until the screens on all cameras are blanked and all the appropriate led's are lit.
When you release the switch and the voltage goes high simply generate a delay equal to about half the camera's shutter speed and use a simple, tiny microcontroller to trigger a triac capable of blocking about 300V.
You do not even need a microcontroller.
I have done this with a 5V DIL relay and a carefully-chosen capacitor.
Circuit diagram in Yahoo SDM Group Files section.
David
