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Looking for USB connectors

Discussion in 'Hobby Electronics' started by skozzy, Apr 17, 2004.

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  1. skozzy

    skozzy Guest

    I want to make a 10 meter long usb cable, I need to be able to connect my
    telescope digital camera to a desktop pc, all the current cables in the
    shops only go upto 3 meters. Is there somewhere selling the connectors ?
  2. skozzy

    skozzy Guest

    Well I was going to setup the pc on a small table outside with the scope,
    but I do need to move the scope around a bit for different views, if I did
    go for a 10 meter cable is the power loss too much or is the signal degraded
    to a point where the comptuer won't see any signal ?
  3. Unbeliever

    Unbeliever Guest

    Unlikely to work due to transmission line effects and speed of light
    limitations (as an astronomer, I expect you'll understand the inevitability
    of the latter). The maximum cable length for USB is 5m. To get 10 meters,
    buy a hub and two 5 meter cables and use those end to end.

    From the USB developer FAQ: "The cable length was limited by a cable delay
    spec of 26ns to allow for reflections to settle at the transmitter before
    the next bit was sent. Since USB uses source termination and voltage-mode
    drivers, this has to be the case, otherwise reflections can pile up and blow
    the driver. This does not mean the line voltage has fully settled by the end
    of the bit; with worst-case undertermination. However, there's been enough
    damping by the end of the bit that the reflection amplitude has been reduced
    to manageable levels. The low speed cable length was limited to 18ns to keep
    transmission line effects from impacting low speed signals."

  4. skozzy

    skozzy Guest

    OK, well that makes sence now. So a hub it is and 2 cables.
  5. skozzy

    skozzy Guest

    Thanks for the offer, but the hub and 2 cables seems like a fairly good
    option, at least I can use the hub for other things too.
  6. Rob

    Rob Guest

    I think you will have problems extending the length over 5m which AFAIK is
    the USB length spec limit.
    There are "repeater/regenerator" cables available to do what you want. I
    don't know the cost of these ($50??). Farnell sell some of the connectors.
    Can you cut a hole in your roof and bring the telescope inside or move your

  7. FWIW should you need the plugs and sockets, Jaycar stock them.
  8. Unbeliever

    Unbeliever Guest

    I get lots of e-mails offering length extensions, they're not USB specific
  9. Alan

    Alan Guest

    I saw some USB "repeater" cables at Jaycar that are supposed to give
    extended distances.


    They are 5m long and apparently they claim you can use up to 5 in
    series to get 25m. Not cheap though at AUS34.95 each



    Jenal Communications
    Manufacturers and Suppliers of HF Selcall
    P O Box 1108, Morley, WA, 6943
    Tel: +61 8 9370 5533 Fax +61 8 9370 5106
    Web Site:
  10. mikegw

    mikegw Guest

    And you have to watch out for signal reflections.
  11. Rob

    Rob Guest

    Probably more related to signal droop. IIRC, capacity is inversely
    proportional to age.
  12. Mark Harriss

    Mark Harriss Guest

    not to mention impedance mismatch
  13. Rob
    I think DSE sell some 5 m cables which can be joined together. Up to 5
    can be joined.
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