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How long can USB cable be?

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#1 James Cunningham

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Posted 18 March 2012 - 09:12 AM

How long can the USB cable from camera to computer be before the camera stops working? I have a 15 foot cable that works just fine. I need to extend the cable to about 20 feet. If I purchase a 20 ft. cable, will the camera still
operate without problems? I already have one of those active repeater cables but it does not always work (I was using one and the image would suddenly stop).
Thanks.
Jim

#2 redbird

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Posted 18 March 2012 - 11:26 AM

5 meters is the max. (16.4 feet)

#3 MRNUTTY

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Posted 18 March 2012 - 11:40 AM

You can extend it with a powered hub between the lengths. Of course you need power there for it to work. Battery powered USB hub? Never seen one. :-)

#4 redbird

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Posted 18 March 2012 - 11:57 AM

They do make some battery power hubs, I have never used one, so dont no about battery life or how well they will work.

#5 RTLR 12

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Posted 18 March 2012 - 12:09 PM

Here is a 12vdc powered USB hub. A little pricey and appears to have some problems. There are also USB booster cables available for a more reasonable price. I happen to use all 3.0 USB components and have had no trouble with them.

.http://store.mp3car.com/DC_Powered_4_Port_USB_Hub_CNX_P5USB_12v_and_24v_p/adt-015.htm

Stan

#6 James Cunningham

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Posted 18 March 2012 - 12:35 PM

How can you tell if your computer has USB 3 capability. I have a HP pavillion with windows 7.

#7 redbird

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Posted 18 March 2012 - 12:46 PM

USB 3 is just now coming out on some computers, some laptops we brought for work has it. not sure about yours

#8 RTLR 12

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Posted 18 March 2012 - 12:49 PM

You'd have to look up the specs on your computer to see if it has USB 3.0. Even if not, USB 3.0 is backward compatible. Even if your computer does not have 3.0 you will notice a slight improvement with the 3.0 cabling. USB 3.0 has been around for about 4 years now and comes standard on my Toshiba E305.

Stan

#9 James Cunningham

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Posted 18 March 2012 - 12:51 PM

I use express card slot on my laptop. Just ordered a USB 3.0 express card for the computer.

#10 ccs_hello

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Posted 18 March 2012 - 01:02 PM

Jim,

I am going to describe the official/sanctioned method on cascading the USB active repeaters. Such arrangement will work on all use cases, including USB2.0 high-speed (480Mbps) isochronous mode (the most challenging mode, used in few astroCCDimagers and few USB video capture dongles). Total length is 5m x 5 = 25 meters (about 75-80').
See this CN post.

There are other solutions which may work in some limited cases.

Clear Skies!

ccs_hello

#11 ccs_hello

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Posted 18 March 2012 - 01:40 PM

Regarding powered USB 2.0 high-speed hub, I recommend Belkin F5U234 (either v1 or newer version). 4 port is chosen since it's counted as one segment, while 7-port hub is counted as 2 segments (you lose 5 meters here).

AC powered hub is much cheaper than DC powered ones. One can then get a 12V (cigarette plug) DC to 5V 2A step-down inverter to supply power to the (originally AC powered) USB hub.

Clear Skies!

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#12 bluedandelion

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Posted 18 March 2012 - 03:54 PM

There are any number of inexpensive universal dc-to-dc adapters made for use in automobiles: http://www.nextag.co...er/compare-html

Look at the requirements for your USB hub, select the correct settings on one of these and you are good to go. This is what I did all of last year to power my USB hub in the field with a deep cycle marine battery.

Ajay

#13 Phil Sherman

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Posted 19 March 2012 - 12:30 AM

Jim,

I am going to describe the official/sanctioned method on cascading the USB active repeaters. Such arrangement will work on all use cases, including USB2.0 high-speed (480Mbps) isochronous mode (the most challenging mode, used in few astroCCDimagers and few USB video capture dongles). Total length is 5m x 5 = 25 meters (about 75-80').
See this CN post.

There are other solutions which may work in some limited cases.

Clear Skies!

ccs_hello


The limit of 5 linked repeater cables worked without problems on my Win XP system but failed when switching to a new system with Win 7. The newer OS counts hubs differently and requires USB devices to be located no more than 4 cascaded hubs away from the computer. My 7-port USB hub contains two cascaded 4-port controllers which limits me to two active repeater cables between the hub and the computer. The maximum distance for USB cabling now becomes 15m from the computer to the hub. This is two active repeater cables and one 5m cable.

My hub at the mount is powered from the same 12v battery that runs the mount. I have a 12v in 5v out regulated supply to feed the USB hub and have had no problems running all of the USB devices, including two DSI cameras.

Phil

#14 johnpd

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Posted 19 March 2012 - 05:08 AM

Jim,

I got one of these (PTC 15M 49ft USB 2.0 Active Repeater) and connected a web cam to my PC and it worked fine. It has two repeaters in it.

JohnD

#15 budman1961

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Posted 19 March 2012 - 12:27 PM

Here is the 64 footer I use without any issues! 20 meter cable

#16 ccs_hello

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Posted 19 March 2012 - 05:35 PM

The limit of 5 linked repeater cables worked without problems on my Win XP system but failed when switching to a new system with Win 7. The newer OS counts hubs differently and requires USB devices to be located no more than 4 cascaded hubs away from the computer.
...

Phil,

I suspect it's your PC hardware issue, not caused by Win7. Please see the attached picture. It's from my desktop PC running Win7-64bit with 4 active-repeater cable segments followed by one powered 4-port hub. I use "UVCview.x86" program to show my configuration.

The PC's south bridge i82801G (ICH7) has multiple Enhanced USB Host Controllers. Each controller has a "Root Hub".
(Note: root hub is not real USB hub and should not be counted as part of "total of 5" cascaded USB hubs.)

Now take a look at the last USB Host Controller (address 27CC). Underneath its "Root Hub", it has 8 ports (I only show 2 in the picture for brevity). Port 1 is the one I used. You can count that there are 5 USB Hub used. (Note: Active repeater is a hub.)

Clear Skies!

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#17 NorthBoundTrain

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Posted 20 March 2012 - 05:49 AM

I have always heard ( not fact to my knowledge ) that 20 is the limit before using a hub. I personally have 15' cables for my USB 2.0's never had a problem. My laptop also has a 3.0 on it, hope to test it out someday soon.

Good luck!

#18 ccs_hello

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Posted 20 March 2012 - 06:32 AM

USB spec stated that 5 meters (16.5') before the protocol (not just the electric signal) needs to be regenerated. That's what a hub (active-repeater) is for. 20' is pushing the envelop and betting on the luck.

Clear Skies!

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#19 Phil Sherman

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Posted 21 March 2012 - 08:37 AM

I suspect it's your PC hardware issue, not caused by Win7. Please see the attached picture.


It may be a difference in how my new laptop's USB ports are set up. The only way to verify this would be to install XP on my Win 7 laptop. Unfortunately, I don't have the disk space to do this.

My old XP laptop and my desktop system allowed me to use three repeater cables then a 2-chip cascaded hub, totalling 5 external chained hubs between the computer and the devices. Win7, on the new laptop, would only allow a single chip hub (4 ports) and complained about the 8-port, 2-chip one.

I'll try to check the hubbing on the Win7 system next time I'm set up for imaging and running Windows.

Phil






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