Solved Why are my USB hubs disconnecting with light switches ?

December 4, 2016 at 16:25:54
Specs: Win 10 , I7
I have Unstable USB hubs connected to my PC , that are tripped by any change of load on the electrical circuits in the property

For example When a light is switched off or on , the usb hub disconnects then reconnects
Even if I plug in a small battery 600Mah into a usb outlet on the ring , the hub disconnects then reconnects

I have a powered hub which is high up on a shelf ( about 5 meters ) , which is connected via Cat 5 ( using cheap passive adapters ) , the cat 5 cable is fished with a 240V lead into trunking . My first gut feeling could be the Cat 5 is acting like an antenna , it is picking up interference which is causing it to disconnect

I am thinking about running some untwisted cable instead , would this make any difference ?

My other thought was that perhaps the 5M run is loosing voltage

Any other suggestions ?

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December 4, 2016 at 18:33:36
To isolate the problem, move everything to another house/site & test.

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December 4, 2016 at 20:16:25
I would say you may be getting interference from the 240AC cable you are paralleling.

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December 4, 2016 at 20:45:15
✔ Best Answer
Each time the AC cycles (50/60 cycles/sec) and even more when load is increased or reduced there is a magnetic field generated around the power wire. This field can induce a current into the parallel wire, in this case your Cat5 wire. This is causing a trip to the hub and a reset. You need to move the wire so most of it is not close and parallel or shield it.

You have to be a little bit crazy to keep you from going insane.

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Related Solutions

December 4, 2016 at 21:03:02
5 meter unshielded cat5 cable together with an AC power cable? That is looking for trouble. Cable length is on the max for USB 2.
What is connected to the hub that need to be so far away from the PC?



A USB twisted pair, where the Data+ and Data− conductors are twisted together in a double helix. The wires are enclosed in a further layer of shielding.
The D± signals used by low, full, and high speed are carried over a twisted pair (typically, unshielded) to reduce noise and crosstalk. SuperSpeed uses separate transmit and receive differential pairs, which additionally require shielding (typically, shielded twisted pair but twinax is also mentioned by the specification). Thus, to support SuperSpeed data transmission, cables contain twice as many wires and are thus larger in diameter.[82]

The USB 1.1 standard specifies that a standard cable can have a maximum length of 3 meters with devices operating at full speed (12 Mbit/s), and a maximum length of 5 meters with devices operating at low speed (1.5 Mbit/s).[83][84]

USB 2.0 provides for a maximum cable length of 5 meters for devices running at high speed (480 Mbit/s). The primary reason for this limit is the maximum allowed round-trip delay of about 1.5 μs. If USB host commands are unanswered by the USB device within the allowed time, the host considers the command lost. When adding USB device response time, delays from the maximum number of hubs added to the delays from connecting cables, the maximum acceptable delay per cable amounts to 26 ns.[85] The USB 2.0 specification requires that cable delay be less than 5.2 ns per meter (192000 km/s, which is close to the maximum achievable transmission speed for standard copper wire).

The USB 3.0 standard does not directly specify a maximum cable length, requiring only that all cables meet an electrical specification: for copper cabling with AWG 26 wires the maximum practical length is 3 meters (9.8 ft).[86]

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December 5, 2016 at 01:34:16
It is definitely interference from the 240V , this does not effect the Ethernet as such ( seperate parallel for the NAS on shelf ) but , it is effecting the 'USB over ethernet'

I believe this is happening because the twisted pair is acting acting almost as an induction coil

As a solution I was thinking running an untwisted cable ? It is going through a drywall so a molded 'Active USB' would have been out the question as the cable would have been to difficult to fish through the cable route

I would submit a picture if I had one ( maybe later ) but my desk is under stairs and the space on the desk is limited , so I am running cable through the voids on the staircase to a shelf . on the shelf I have a plethora of gadgetry including a NAS

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December 5, 2016 at 02:22:44
I just got a batch of USB terminals , I am thinking to run an active extension , cutting the molded end ( So I can pull it through the route) , then terminating it to my device hub .

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December 5, 2016 at 10:16:32
For longer distances you can look into a USB repeater cable.

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December 5, 2016 at 19:48:46
I think you are better of with a USB over Ethernet device.

Google usb hub over ethernet

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December 6, 2016 at 03:46:47
I dont think I can justify an active USB over Ethernet device for a cable run of 5 Meters at home .

I will just run a shielded USB cable with an Active repeater to see if that stabilizes things . The passive Ethernet cables were creating a magnetic induction field which seems to voltage instability

Hopefully the shielded USB cable will rectify this

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