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DIY USB Extension Cables Using Cat5/6?
TheDarkRogue asks: "Ok, I have a small USB device that I need to position a distance from my computer, more then the cable, at least 30 feet. The thing is that I don't think it can go that far very well. I looked around for a solution and found a few products I could get for a price way out of my price range, so now I'm looking at this as a doit-myselfer. How can I extend the distance using Cat5/6? Does anyone know of any schematics for something or is that in its self more then is needed?" Extending a USB cable to this length (or more) can't be this easy, can it? What's the maximum length of USB cabling one can get in a single stretch?
http://www.google.com/search?q=usb+maximum+cable+l ength+specification
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http://www.google.com/search?q=usb+extension+cabl
Slashdot is jumping the shark. I'm just driving the boat.
Can long cables really be this easy? Maybe...
I dunno, I needed to network two machines QUITE a distance apart, so I made a crossover UTP network cable out of an existing UTP patch cord and several hundred feet of speaker wire, as two pairs (send pair and receive pair).
Works perfectly. Blazing fast, too. I would say that I just got lucky but I do these sorts of things all the time....
You may very well be successful with the Cat5/6 option. My excessively-long ethernet cable made out of speaker wire has been functioning flawlessly for months (in fact, I built another to network hubs at vertically and horizontally opposite corners of my household, and it has also worked like a charm).
--TheOrangeSquid Is it any wonder things seem so awry? We swim in a sea of confusion and don't have to think to survive
"For a low speed device the limit is 3 meters (9 feet 10 inches)."
From USB.ORG's USB Info: Frequently Asked Questions
In practice, manufacturer's technical support representatives often say that their devices will not work with a cable longer than 2 meters (6 feet), and they supply a cable of that length. In many office situations, a cable that short is useless. But they are right, a longer cable doesn't work, and a hub doesn't work.
Ethernet and FireWire are examples of properly designed computer communication interfaces. They are trouble free.
USB 1.0 is an example of a poorly designed and poorly implemented interface. USB often interferes with computer hibernation, to give another example.
I always end up posting to my own posts...
Checkout BeyondLogic if you are interested in interfacing custom hardware as they have alot of good documentation on Serial/Parallel/USB Devices/Programming/etc. Slashdotting this site may be cruel so only go if you really are interested in interfacing at home. =)
Pixels keep you awake!
You can't just go hacking into a USB cable and make it longer. Probably the #1 reason is that USB uses a differential signal. That means that however you extend the cable you have to do it exactly the same on both D+ and D-. If you don't, part of your diff signal gets skewed and becomes corrupted at the receiver. Secondly you have to maintain an imepedance match. Anytime you introduce an impedance mismatch you generate reflections. The wire used in a USB cable has a certain about of reactiance (X). The X of a twisted wire pair is completely different.
In order to do what you want, you really need to build a fairly preceision amplifier/receiver setup. The difficulty is the fact that you are dealing with differential signals. Each "side" of the diff signal must be treated the same way. It is almost impossible for you to make the exact same size solder joints, exact same size wires, and have the exact same impedances throughout. Its especially important on long runs because of the highly immentant signal attenuation.
From The USB FAQ
Q3: Why can't I use a cable longer than 3 or 5m?
A3: USB's electrical design doesn't allow it. When USB was designed, a decision was made to handle the propagation of electromagnetic fields on USB data lines in a way that limited the maximum length of a USB cable to something in the range of 4m. This method has a number of advantages and, since USB is intended for a desktop environment, the range limitations were deemed acceptable. If you're familiar with transmission line theory and want more detail on this topic, take a look at the USB signals section of the developers FAQ.
Essentially, the USB cable is a mismatched transmission line. As a result, the signal reflects off of the ends of the cable, resulting in a stair-step pattern whenever the voltage level on the line changes. As the cable gets longer, it takes more time for this stair-step pattern to settle to the final voltage.
Come test your mettle in the world of Alter Aeon!
I read this story earlier and just happened across this device a minute ago:
16 ft. USB Active Extension Cable
I have ZERO relation to this company (though I have bought from them before) and have ZERO experience with the product. But it looks like what you're after. I'm sure there are other vendors who supply this device as well.
Good luck!
As an anonymous coward has pointed out this is a mis-reading of the KDS page. To get the 80 foot extension you have to connect 5 x 16 foot extension cables. I am repeating the anonymous coward's observation as I have a higher karma rating.