[kwlug-disc] USB 2.0 hubs, and power ...

[Khalid Baheyeldin]

On Tue, Oct 29, 2019 at 9:42 PM Andrew Kohlsmith (mailing lists account) <
aklists at mixdown.ca> wrote:

> > On Oct 29, 2019, at 9:36 PM, Khalid Baheyeldin <kb at 2bits.com> wrote:
> > I used the "USB Safety Tester" dongle, and when the camera is taking
> images, it only registers at 0.04A, so 40mA, well within the range of any
> unpowered USB 2.0 hub.
> > Yes, I hear ya all about how the cables are what matters, and I will
> have to experiment with a few.
>
> If that truly is the current draw when operating then there is no way even
> a long, crappy extension cable will cause enough voltage drop to cause any
> issues. 200mW is a pretty low-power device and you’d have to have a cable
> with a resistance in the area of 6 ohms to drop the USB voltage by 5%.
>

The test I did was 100 exposures of 2 seconds each, over a 5 minute period.

The other relevant figures that the dongle reported are as follows:

Cap: 1 mAh
Ene: 0.009 Wh

Do they make sense?
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