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Thread: Extend USB cable?

  1. #11
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    Re: Extend USB cable?

    If you make a USB to RJ45 connector make sure to mark it with some warning color or your mom/room mate might plug the wrong thing in

    RJ45 has a voltage span of -2.5 to +2.5, while USB uses GND to +5V any way connected to a wrong port and you might have serious problems - even static kills a mobo.

    Ever thought of buying a WIFI router, that has "surveillance mode" for a USB cam?
    Don't ask what your company can do for you.
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  2. #12
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    Re: Extend USB cable?

    Quote Originally Posted by An Sanct View Post
    If you make a USB to RJ45 connector make sure to mark it with some warning color or your mom/room mate might plug the wrong thing in

    RJ45 has a voltage span of -2.5 to +2.5, while USB uses GND to +5V any way connected to a wrong port and you might have serious problems - even static kills a mobo.

    Ever thought of buying a WIFI router, that has "surveillance mode" for a USB cam?
    Hmm. Interesting. Another option might be camera plugged into router then ethernet cable out of there (up to 100M) to wherever (the LAN router computer connects to or surveillance recording box). Options ...

  3. #13
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    Re: Extend USB cable?

    Well, I have thought of Wifi routers but the problem is all the camera's wont be in the same place so I would need more than 1 router But I found a intructable which might just work. I'm gonna try it after my exams

    Here the instructable :
    http://www.instructables.com/id/How-to-Extend-yout-USB-using-UTP/
    Ab Aeterno Scientia Potentia est

    http://thevoid.in/

  4. #14
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    Re: Extend USB cable?

    Quote Originally Posted by cyb3r_sn4k3 View Post
    The webcams are USB and I'm planning to use 6MP or more. Though I dont have no official degree in electronics or anything (Im still goin to school ) one thing I have learned is that the normal USB cable have very bad insulation so I was just guessing that ethernet cables would be better(pls feel free to correct me ). If extender cables are needed I would have to make my own lol because its kinda hard to find them where I live.
    the problem is that usb is not specified ground free. The differential impedance is some 90 ohm, while the ethernet cable is 100 ohm, the impedance is very similar.
    However usb is designed to operate each of the data wires with ground reference. It is not real twisted pair connection. It is terminated with 45 ohm on each data wire to gnd and not floating as ethernet system is.

    This is the main reason why what you want do will not work unless you use so called usb repeaters. Those are almost small computers, that means active parts, receiving the signals, shaping them and transmitting again. And this you will need every 3-5 m again and again.

    The whole has zero to do with insulation etc, it has to do with physical specs of the connection system in its complete state.

    Both systems are designed so that they work reliably only when specs of cables, connectors, terminals are fully met and matched to each other.

    So you can not start with usb connector, then open the cable and solder to it some other cable. This alone will give you mismatch node which will probably make the usb signal travel 2m instead 5 already. So there is no way to make your own adapters or cables unless you have vector network analyzer to hand and are able to produce matching circuits for each change of impedance.

    **So forget all your plans***,
    and if you want build video distribution, then get an ethernet connected camera , this is way cheaper then all those repeaters every few meters.

    no need for discussion, take the facts only:
    http://www.usb.org/developers/compli...Spec081005.pdf



    BTW: at work, we made real professional testing with cat6 cable, exactly 100m, straight on the ground, no twists, no bends etc. Result was over 50% of lost packages on base100 connection.
    Last edited by ottosykora; March 7th, 2012 at 07:46 AM.

  5. #15
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    Re: Extend USB cable?

    Quote Originally Posted by ottosykora View Post
    the problem is that usb is not specified ground free. The differential impedance is some 90 ohm, while the ethernet cable is 100 ohm, the impedance is very similar.
    However usb is designed to operate each of the data wires with ground reference. It is not real twisted pair connection. It is terminated with 45 ohm on each data wire to gnd and not floating as ethernet system is.

    This is the main reason why what you want do will not work unless you use so called usb repeaters. Those are almost small computers, that means active parts, receiving the signals, shaping them and transmitting again. And this you will need every 3-5 m again and again.

    The whole has zero to do with insulation etc, it has to do with physical specs of the connection system in its complete state.

    Both systems are designed so that they work reliably only when specs of cables, connectors, terminals are fully met and matched to each other.

    So you can not start with usb connector, then open the cable and solder to it some other cable. This alone will give you mismatch node which will probably make the usb signal travel 2m instead 5 already. So there is no way to make your own adapters or cables unless you have vector network analyzer to hand and are able to produce matching circuits for each change of impedance.

    **So forget all your plans***,
    and if you want build video distribution, then get an ethernet connected camera , this is way cheaper then all those repeaters every few meters.

    no need for discussion, take the facts only:
    http://www.usb.org/developers/compli...Spec081005.pdf



    BTW: at work, we made real professional testing with cat6 cable, exactly 100m, straight on the ground, no twists, no bends etc. Result was over 50% of lost packages on base100 connection.

    Thank You, that was very informative. I will take up on ur advice
    Ab Aeterno Scientia Potentia est

    http://thevoid.in/

  6. #16
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    Re: Extend USB cable?

    Hay,

    This is truely one of those "why the h*** not??" questions.

    Like ottosykora said, the USB 2.0 specs dictates a very short cable, under 5m. This is the exact same reason as why some products work with an unpowered USB-Hub, and some don't.

    The THEORATICAL limit of a USB cable reach is 10m: PC > 5m Cable > Powered USB-Hub > 5m Cable...



    However I have experimented with some longer "active" cables. They work good on 1.1, but 2.0 slows down...

    However if you are an electronics student (even school level) you can build a 741xx Op Amp Circuit with adjustable gain from 1:1 - 1:3 (Please bare in mind this is a two way comunication channel so using the dual packages available will be greatly better) as to boost the data signals. Using a 5v 1A power supply should allow for enough juice in the cable, just add a diode on the +Vcc to keep the spillage from hitting your motherboard.

    This is the allaborate approace, I would also suggest getting propper cameras with a DVR card and just running good 'ol RG58 coax from the camera to the card. (using a power injector you don't even need an aditional power cable) or even RG58-Pw which has a twisted pair cable inside aditional, so you can run up to 10Watts of DC current with the coax to where ever the camera will be mounted.

    Good luck though
    Cherz
    Switched away from windows XP to Ubuntu 9.04. Never turned around to look back.

  7. #17
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    Re: Extend USB cable?

    Quote Originally Posted by zero2xiii View Post
    Hay,


    However I have experimented with some longer "active" cables. They work good on 1.1, but 2.0 slows down...

    However if you are an electronics student (even school level) you can build a 741xx Op Amp Circuit with adjustable gain from 1:1 - 1:3 (Please bare in mind this is a two way comunication channel so using the dual packages available will be greatly better) as to boost the data signals. Using a 5v 1A power supply should allow for enough juice in the cable, just add a diode on the +Vcc to keep the spillage from hitting your motherboard.


    Cherz
    The whole problem is not the actual amplification or compensation for loses. This is easy to cope with, as you say an amplifier.

    The major problem here is the impedance of the whole circuit from start to the end. It has to be maintained very close to the specs as otherwise high reflections and thus standing waves on the cable will occur.
    This will lead to cancellation of the signals on cable regardless how strong the signals are.

    Note that with usb we are talking about high frequency connection. Every single peace of the connection has to be designed to be matched by impedance to the next. So the transmitter has to be matched to the connector, the connector to the cable etc.
    If it is not, then we have mismatch node, the energy will be partly reflected back to the transmitter and part will radiate off.

    If an amplifier is included, well it has to be not only amplifying, but also phase stable and have 90 ohm input impedance and 90 ohm output impedance. Layout of the printed board, wire connections and case of the circuit have to be considered carefully and properly matched to result in the overall differential impedance of 90 ohm with 45 ohm against gnd on each active wire.

    The problems that some signals do not pass well some hubs are often partially connected to this, but more is simply lack of 5V power coming out of the passive hubs. Not the mutilated signal is then a problem, but the devices simply will not power on when they see a low power 5V source.

    If the source is flagged to supply only 100mA, devices like external hard drives will simply refuse to do anything at all.

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