USB extension over CAT5 cable

[Bill]

Not sure if anyone has tried this before, but here goes...

I have an existing CAT5 cable running between the downstairs and upstairs of my house, length around 10 metres. Each end terminates on a wallbox.

I'm now in a position where I would like to connect a downstairs USB device (my Topfield PVR) to the PC upstairs.

The run length is too long for USB reliably, so I am considering a USB CAT5 extender. I could run in another CAT5 cable for this, but it would be a bit of a pain. HOWEVER, 10/100 BaseT network connections only use 2 of the 4 available twisted pairs, hence I have 2 spare pairs in my existing cable. It would be a trivial matter inside the wallboxes to split these pairs off to a 2nd RJ45 module and send the CAT 5 side of the extender modules down that. The question is, would it work i.e. does USB over CAT5 cable only use 2 pairs in the same way that real 10/100BaseT signals do?

These modules are quite common, but has anyone ever tried them with a non fully wired CAT5 cable?

[Spike]

Christ knows how many wires the USB converter uses, but in order to split the cat 5 cable into two, do a quick google for cat 5 economisers. I know for a fact that

do them for about 4 notes a pop, and youd need two of them...

[Seri]

Okay, first things, is it a USB 1.1 or a USB 2 device that you want to extend? If it's a USB 2 device then make sure that you don't mind it dropping down to being USB 1.1 performance as USB 2 only has very severe drop off range.

Second, make darn sure that you split the other end of the cable before it plugs into your router/switch/hub/modem/etc other wise you may blow the poor thing up.

Third, be prepared for the performance of the network cable to drop down to about 25mbps due to the ammount of interference on the line (packet collisions, dropped packets, retransmissions etc).

Other than that it's fairly basic wiring. The USB bus is a 4/5 wire bus with the fifth wire commonly used as earth, this nearly always the outer shell of the USB connector. Just make sure that the pins all correspond and your away. No technical challenges what so ever.

Hope this helps a little.

Seri

[Ian Stirling]

The cable doesn't make a difference, you don't get any greater distance by going to CAT5. Obtain a hub. Plug it into the middle of the run, on two 5m cables. Job done.

[Rob Morley]

But he said he was going to use a USB-to-Cat5 extender, which is not the same as just using Cat5 cable with a USB plug on each end.

Better to use an active USB extension cable, which is effectively a single port self-powered hub designed for precisely this purpose.

[Bill]

Precisely, that was my intention. USB-CAT5 extenders are good for several tens of metres of usable distance.

A hub in the middle of the run would end up sitting on the outside wall of the house! Am now looking into active extension cables.

Cheers.

[Chris Hodges]

Unfortunately this isn't how the USB over CAT5 devices work - you would run into the 5m limit straight away. The 5m limit is NOT attenuation, it's timing - signal reflections, and while you can push it to ~6m in 1 section this isn't reliable. The USB-over-CAT5 senders normally show up as a hub (just 1 for the 2 units and cable) becuase the USB timing spec allows for some delay in the hub.

btw USB cabling consists of Data+, Data-, +5V, 0V and screen. D+ and D- are often thinner than the power connectors.

[Chris Hodges]

I have used 2 models. 1 is from CPC, about £30 and seems reliable. The other was around £200 but was one of the first to come on the market a few years ago. I had 2 failures out of 4 (1 DOA, and 1 after about a year). I know for a fact having asked your original question direct to the manufacturer (small UK firm and I got through to the design department) that it uses all 8 cables. IIRC a pair was used for +5V, a pair was used for 0V and the other 2 pairs for the data in a proprietary way. I can't promise this holds for the newer cheaper ones, but it's likely (if you consider wire gauges, currents and voltage drops).

I think it'll have to be a new length of cta5 (or use the old one and run your LAN over wireless)

Chris