[simpits-tech] More on USB

[Matt Bailey]

On Tue, 16 Sep 2014 06:34:49 -0700 (PDT)
geneb <geneb at deltasoft.com> wrote:

> > Your point
> > about isolating the USB interface from the load is a good one, but
> > I don't believe that is what was going on here.
> >
> Try it with the Arduino on a different hub and see if the problem 
> persists.

Thanks for the tip...I usually eschew USB hubs, but on your advice I
will give it a try for the limited USB devices I may use on the
Sabreliner (keyboard and mouse, mainly).

> > 2. The USB cable, or wiring connected to the USB interface, is near
> > some high voltage AC stuff, such as 115v 400hz aircraft power for
> > lighting. I have not observed this myself as I am not dealing with
> > 400hz yet, but I have been told by other folks that it's a
> > nightmare. My understanding is that the magnetic fields produced by
> > the AC voltages in the aircraft lines pass voltage to the wires
> > connected to the USB interface, delivering potentially high
> > voltages to the device. I believe this would also be considered
> > voltage via inductance, no? Or just general electrical noise, at
> > the least.
> >
> This is only a concern if you've got a USB cable running in parallel
> and close proximity to an AC line.  If the USB cable crosses the AC
> line at a 90 degree angle, you should be fine.
> 
> You'll have the same issue with ethernet if you're running it
> parallel to AC lines.
> 
> A good rule of thumb is to keep low voltage stuff on one side of the 
> cockpit and AC stuff to the other.

I realize changing the wiring around can help, but that's not practical
in many cases...especially with the Sabreliner having its ENTIRE wiring
harness still fully intact!!! I didn't know going 90* was a fix for the
AC issue....trouble is, if I did USB to anything inside the cockpit, I
would have very long runs of USB that need to go in the same direction
as existing AC lines (mostly for lighting). Are you saying just a
single 90* bend somewhere would help?

At any rate, yes, if I get ethernet interference, I'll have to deal
with it somehow too. The difference is my UDP programs don't care if
they miss a packet or two here and there, and corrupt packets can be
chucked. Not so with USB.

-- 
Matt Bailey

Keeping It Real:
Sabreliner 60 Flight Simulator
Serial # 306-61 - N1JX
http://sabrelinersim.com