So you’re running the USB power over 14AWG? I thought you were running 14 or 12 for the AC part then a standard USB cable to the cam, so my mistake. That will certainly help minimize voltage drop, though when you’re starting with 5v there still isn’t much to play with, and that large cable will actually be harder for the small USB adapter to energize properly. For some with longer runs (in the 20 to 25 foot range) people have found that simply using a bigger power supply (3+ amps) helps, since the cam draws more current when the voltage is lower, and that can help compensate. But over 25 that doesn’t seem to help unless a really good USB cable is used too, and it varies based on camera model.
Some caps would certainly help, though I think you’ll find sustained moving of the camera, especially with the spotlight on, might need quite a bit of capacitance. I’m also curious how a full charge up of the caps would be handled by the power supply. I suppose it is a short enough period that it shouldn’t matter, but it will stress it some.
Yes I agree that data is far more sensitive. Shielded cables can help with that (which most non-flat USB cables are), but it also heavily depends on the ability to do pretty complex encoding which needs nice sharp square waves and the proper minimum and maximum voltage. You could have a perfectly shielded USB cable with 100% coverage and 0 interference and the signal will still be a mess at the other end. Some of it from crosstalk, but the rest just from the compressing down of the voltage range causing the different amplitudes to be too close to be differentiated, and thus those bits are dropped. It isn’t really timing, the latency of a 9M run is virtually 0, just that the amplitude modulation simply can’t get the number of distinct levels it needs anymore.
Another thing people have done is put a USB power bank in the path near the cam. It has to be one that supports charging and supplying power at the same time. But that’s an expensive solution, unless you’re also looking for some battery backup ability. But it also essentially acts as a big capacitor.
I know 9M doesn’t seem like a long run for power but for 5V DC on normal USB cables (usually 28awg, or if you get a good one, it will have 24 for the power and 28 for signal), 9M is actually really far. I suspect one of the ones with 24 for power, combined with a good quality AC adapter, might be able to do it. But it is all trial and error at that point.
Well be sure to report back your results, this is something that others run into from time to time. Though I think most do not have the ability to rig up their own fix and in their case the PoE solution is probably easiest and most reliable. I guess I have two categories of things, stuff I like to tinker and toy with and optimize over time, and others (like my cams) where I just want them to work and not have to spend time on them. If you’re running 14AWG to the cam, beefing up your power supply may be all that is needed.