Advantages to using this over regular USB +5v:
1) Doesn't require a +5v source, just need to connect the pins (6 and 11 per achilllies doc linked above)
2) Doesn't need software hacks to work at the same time as PTP
3) For large multicam rigs, don't deal with cutting power after the hubs
I don't know how I missed, until now, this and related "
HDMI power and alternative remote inputs" threads - very interesting.
I'm not up to speed on either yet but don't wish to hold back with the following query - does
Point 1 above infer pin 6&11 must be closed by a physical relay, similarly to:
The advantage of this is that the reed switch would just need to switch to ground or open circuit (or open circuit and the original terminal), not +5v.
?I tested Hardware_Hackers suggested USB Adapters (
https://chdk.setepontos.com/index.php?topic=13294.msg136643#msg136643) hacked to include a normal switch cable on the output side of the hubs a while ago and, in limited testing of a 16 number camera system, ptp reliability seemed very good while a precision sync build (without detailed results to confirm) "seemed" to provide very good precision.
However, I am, perhaps mistakenly, concerned that the loose coupling of the switch cable supply and return paths could result in creating a very large loop antennae and problems as the system is expanded - the video cable solution would be very much more tightly coupled, presumably, decreasing any possible ill effect from that. On the other hand, if relatively slow mechanical relays are the only way to short pin 6&11 (preferably under microprocessor control) it seems "good" precision sync would not be obtainable across a large camera count.
I know (admittedly little circuit design experience) of no electronic component that can simply replace a mechanical relay (without understanding the behaviour of the circuit in which the substitution is imagined to take place).
Is the camera video output circuity (camera side of pins 6&11) understood to any extent that, for example, an externally connected photodiode (or amplifying phototransistor) is sufficiently reversed biased that on (associated optoisolator) LED light production the tiny reverse saturation current increases sufficiently to "short" pin 6&11 in a fashion functionally equivalent to a relay?
