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Hardware Thread, Promethean WB USB cable extending in Technical; Hi All, Wondering if any of you have experience of extending the USB cable length connecting a computer and recent ...
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    Promethean WB USB cable extending

    Hi All,

    Wondering if any of you have experience of extending the USB cable length connecting a computer and recent versions of Promethean whiteboards. I'm looking at extending the range with some kind of booster as the length of cable we need may be too long to reach on its own.

    Thanks,

    Tim

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    plexer's Avatar
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    There pretty long as standard why would you need to extend it?

    If the computer/laptop is that far away it wasn't well planned.

    Ben

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    Sometimes the layout of the room structure affects where you want to put the IWB faceplate. We had one here with an installation that had to have the connections in the trunking, through the ceilinig and down the wall to the teachers desk. We have had problems every since. We have an intermittant problem where the IWB does not get detected, sometimes a reboot will fix it sometimes not. I have reimaged the machine to make sure it was not the hardware, and eventually got the problem down to either the length of USB cable used or the faceplate it is fixed to.

    I am still waiting for the company that fixed it to come back and check the installation that was done last year. The cable used did not have a booster on and I suspect that we will need to sort it out as a school rather than rely on the installation guys to come back and fix it.

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    my guide on what I've seen working.

    USB can be extended but only with active usb extenders (I mean active as in power, not a silly product name). No more than 5m between boosters. Should go up to 15-20m but depends on the quality of the USB chipset on the machine.

    I would also recommend you only use Activdriver 4.1.13 with this setup, as there are a lot of fixes in it for disconnected Activboards that are connected through usb hubs or repeaters.

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    There's a more effective way to extend the length of the USB cable without degrading the performance. Also, by lengthening the USB cable, even with signal boosters, you can experience loss of signal between the board and the host PC.

    Several companies make USB/RJ45 adapter kits. They cost about 3 - 5 US dollars in bulk. You connect the USB cable from the board to the adapter, then run your ethernet cable whereever you need it; across the room etc... Then you connect the other half of the adapter to the RJ45 on the ethernet cable, and plug the male USB end into the PC. Viola. We use them all the time on wall mount installations - in about 300 installations we've had only two fail.


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    AlphaJoker - Out of interest why is USB so rubbish over distance when basically its just electricals going over copper cable like anything else??

    Butuz

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    AlphaJoker's Avatar
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    Wink

    Butuz, here's a snippet of information for you on USB design (along with inherent flaws):

    The maximum length of a standard USB cable is ~ 5.0 meters. The primary reason for this limit is the maximum allowed round-trip delay of about 1500 ns. If a USB device does not answer to host commands within the allowed time, the host considers the command to be lost. When adding up the USB device response time, delays from using the maximum number of hubs, and delays from the connecting cables, the maximum acceptable delay per cable turns out to be 26 ns.[13] The USB 2.0 specification requires cable delay to be less than 5.2 ns per meter (which is close to the maximum achievable speed for standard copper cable)."Propagation Delay". This allows for a 5 meter cable.

    Basically, this states that the device on the end of the USB cable will only wait about 15ns for an answer, and if it recieves none your computer sees that the device has been disconnected. With the Promethean boards that this happens to, you'll hear the electronics beep over and over again.

    If you want more info on USB, simply visit www.usb.org.

  8. 2 Thanks to AlphaJoker:

    AngryTechnician (18th November 2008), dhicks (18th November 2008)

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