USB cable extention

[hpibmx]

Hi,

could anyone explain how to extend usb cable? I simply got female usb and added all 4 lines, but it doesn't work, it does work for led light but for data it doesn't work, when using camera or anything else.

I would to know the reason and explanation for this please.

Thank you.

[mariush]

Wires have resistance ... the longer the wire, the higher the resistance and the voltage drops.
According to Ohm's law : Voltage = Current x Resistance

let's say the wire has a resistance of 0.1 ohm per meter and you have a 3 meter long usb cable, that means in total there's 6 meters of wire between the device and the power supply that puts 5v on the usb cable... the higher the power consumption, the more losses will be on the cable.
Let's say your camera consumes 5 watts (5v x 1A of current)
So at the end of the USB cable, instead of 5v you would have 5v minus a voltage loss of   V = current x resistance = 1A X (6 METERS of wire x 0.1 ohm ) = 1 x 0.6 = 0.6v

The camera may not start with 4.4v ... too low voltage.

There are also some rules about the length of the data wires, and how long it takes for bits to travel, the longer the wires the more issues there are with clocking the bits and decoding the bits correctly.


IF the power is the issue, you can solve that by using thicker wires, or more wires.. for example you could use an ethernet cable with its 8 wires to extend a usb 2 cable .. you would use 2 wires for each of the 4 wires of the usb 2 cable... you use 2 awg24 wires instead of a single awg22-awg26 wire so you have less resistance... and the wires inside ethernet cable are also twisted so you get a bit better signal quality.

[hpibmx]

Wires have resistance ... the longer the wire, the higher the resistance and the voltage drops.
According to Ohm's law : Voltage = Current x Resistance

let's say the wire has a resistance of 0.1 ohm per meter and you have a 3 meter long usb cable, that means in total there's 6 meters of wire between the device and the power supply that puts 5v on the usb cable... the higher the power consumption, the more losses will be on the cable.
Let's say your camera consumes 5 watts (5v x 1A of current)
So at the end of the USB cable, instead of 5v you would have 5v minus a voltage loss of   V = current x resistance = 1A X (6 METERS of wire x 0.1 ohm ) = 1 x 0.6 = 0.6v

The camera may not start with 4.4v ... too low voltage.

There are also some rules about the length of the data wires, and how long it takes for bits to travel, the longer the wires the more issues there are with clocking the bits and decoding the bits correctly.


IF the power is the issue, you can solve that by using thicker wires, or more wires.. for example you could use an ethernet cable with its 8 wires to extend a usb 2 cable .. you would use 2 wires for each of the 4 wires of the usb 2 cable... you use 2 awg24 wires instead of a single awg22-awg26 wire so you have less resistance... and the wires inside ethernet cable are also twisted so you get a bit better signal quality.

Great thank you for your explanation.
I'll try thicker cable or ethernet as you mentioned. 

[m3vuv]

how long is it?

[magic]

Check your wire order. Normally it's black, green, white, red respectively for ground, D+, D-, power.

You should get best performance using proper USB cables (characteristic impedance 90Ω, which is a measure of AC signal propagation characteristics and has little to do with resistance between the ends). Ethernet might work. But your cable doesn't even look like D+/D- are twisted together, so it may only be effective over shorter distances than proper high speed data cables.

Try some low speed devices like keyboards or mice, they ought to be more tolerant of poor cabling and may tell you whether the problem is with signal quality or missing/swapped data lines, for example.

Measure the 5V at the end with the device connected, this will tell you if there is a problem with voltage drop along the way.

I recall that USB is not recommended for distances longer than a few meters, but I don't know how it fails exactly and how far could you push it with good cables.

[Bassman59]

I recall that USB is not recommended for distances longer than a few meters, but I don't know how it fails exactly and how far could you push it with good cables.

USB 2.0 has a length limit of 5 meters, set by the turnaround time of a response from a device to the host. If the cable is too long, the host won't see the response in time and assume the device is not functioning correctly.

USB 3.0 superspeed has no length spec as such but the cables need to be "short" for the same reason as with 2.0.

[cdev]

I have a USB extension cable thats around 5 meters long. It shows up and acts as a hub. I use it with my RTL-SDR to put the receiver far away from my desktop/monitor. and its RFI.   (or even upstairs) It works well and substitutes for coaxial cable well in that kind of setting. It lets me put the SDR up much higher + closer to the antenna and snake the cable down to where  I have my computer. Coax and its losses at UHF make this a far better way to do this. The small size of the USB dongles lends itself to this too. Some might even contain a DC-DC converter to raise the voltage a bit? (But I am pretty sure mine doesn't, as that would add unwanted noise)

[voltsandjolts]

Example products that might help if you need longer extension:
https://www.lindy.co.uk/usb-c4/usb-extension-c222

[Terry Bites]

buy an extender?

[hpibmx]

Check your wire order. Normally it's black, green, white, red respectively for ground, D+, D-, power.

You should get best performance using proper USB cables (characteristic impedance 90Ω, which is a measure of AC signal propagation characteristics and has little to do with resistance between the ends). Ethernet might work. But your cable doesn't even look like D+/D- are twisted together, so it may only be effective over shorter distances than proper high speed data cables.
Try some low speed devices like keyboards or mice, they ought to be more tolerant of poor cabling and may tell you whether the problem is with signal quality or missing/swapped data lines, for example.

Measure the 5V at the end with the device connected, this will tell you if there is a problem with voltage drop along the way.

I recall that USB is not recommended for distances longer than a few meters, but I don't know how it fails exactly and how far could you push it with good cables.

Yes will try lower speed devices and I’ll measure the voltage definitely.

Thank your explanation.

[hpibmx]

Example products that might help if you need longer extension:
https://www.lindy.co.uk/usb-c4/usb-extension-c222

Thanks for pointing out, soo what’s the magic the cable quality? Or what makes it work longer cable? As @magic mentioned the voltage drop?

[Bassman59]

I have a USB extension cable thats around 5 meters long. It shows up and acts as a hub.

The hub is the key!

[Bassman59]

Example products that might help if you need longer extension:
https://www.lindy.co.uk/usb-c4/usb-extension-c222

Thanks for pointing out, soo what’s the magic the cable quality? Or what makes it work longer cable? As @magic mentioned the voltage drop?

The extender has a USB hub built in. That gives you an extra 5 meters of distance. The USB 2.0 spec is that the distance between a device an a hub must be no more than 5 meters, so you can go 5 m from computer to hub, then another 5 m from hub to device. Remember, though, that these extenders are bus powered, so if you have a bus powered device at the end of the wire, it can't draw more than 500 mA minus whatever the extension draws. And some bus-powered devices just claim that they use 500 mA so they won't enumerate with these extensions.