[mythtv-users] OT: USB inductance (or other) problems with external peripherals

[Stephen P. Villano]

On 10/14/13 1:02 PM, Gary Buhrmaster wrote:
> On Mon, Oct 14, 2013 at 4:44 PM, marcus hall <marcus at tuells.org> wrote:
> .....
>> All of the wires in the conduit certainly *must* be rated for the highest
>> voltage carried by any conductor in the conduit.
> More than just the voltage.  There is also the heat
> rating, and the problem of the exposed ends on the
> LV cabling, and the requirement that any of the
> devices that such cables be plugged into themselves
> be safe at those voltages (what do you think will
> happen to your PC if the USB port receives mains
> voltages, let alone your fingers touching the metal
> connection on the USB cable at mains voltages?)
>
> As with all else, in the codes, there are often other
> mitigations that are sometimes acceptable.  But
> unless you really understand all the issues, just
> say no to sharing conduits.
>
> Gary
> _______________________________________________
At a minimum, I'd have run a separate LV conduit. I'd also have the
conduit grounded, to better reduce hum.
I've ran grounded conduits many times over the years for both low
voltage signal cables and for mains supply cables. Never had problems
and the conduit acted as a ground bus, as in long runs, we drove new
grounds into the earth or  to metallic water pipes, depending on the
situation and current electrical code.