EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: Flump on August 13, 2014, 10:06:00 am
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How do you guys decide what USB extension to buy
do you just buy one that looks good and take a chance
or do you stick to a specific brand or something else ?
I just got one from ebay which looked great and he sold
over 12000 of them but testing it for charge current
I got about 60mA out the other end of it when I plugged
my torch in to it which should have drawn about 370mA
http://www.ebay.co.uk/itm/370782294942?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.co.uk/itm/370782294942?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
resistence from one end of each wire to the other is around 1.6R
and thats a 1mm drill bit in the picture
(http://www.drop22.com/images/usbcable/P8130013%20%28Medium%29.JPG)
(http://www.drop22.com/images/usbcable/P8130018%20%28Medium%29.JPG)
(http://www.drop22.com/images/usbcable/P8130020%20%28Medium%29.JPG)
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Technically, USB extensions are not USB compliant. If you insist on using them, get the thickest gauge power conductors you can find. As for data, if you are transmitting anything at hi-speed you might have problems. If you need to extend USB for some reason, use a powered hub.
If you want to stay within spec for cables (which I have found is necessary if you want to charge modern mobile devices with a dedicated charger) stick to the USB 2.0 cable guidelines for power conductors:
28AWG for <= 0.81m
26AWG for <= 1.31m
24AWG for <= 2.08m
22AWG for <= 3.33m
20AWG for <= 5.0m
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There are *good* usb extensions out there - but none I've seen will really suit charging applications.
The best cables (I have 2 x 10m in my goodie box) use a couple mA of power from the source - to reshape/reclock the data pins.
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Very good question. There is a lot of junk USB cables around. Not only from eBay but also from your local computer store. I have seen similar things with normal USB cables, not extension cables. Some I/O devices such as cameras won't work with crap cables. The only ones I trust is those supplied with brand name equipment, and also my never failing Microchip PICkit/3 red mini USB cable. Looking at the price on eBay, you got what you paid for.
Maybe something like this is better...3M USB 3.0 SuperSpeed Extension Cable Insulation Protected Male to Female MF (http://3M USB 3.0 SuperSpeed Extension Cable Insulation Protected Male to Female MF)
or this... http://www.ebay.com.au/itm/High-USB-3-0-Type-A-Male-to-Female-Connector-Extension-Cable-Adapter-Blue-/161377525870?pt=AU_Laptop_Accessories&hash=item2592d9a06e&_uhb=1 (http://www.ebay.com.au/itm/High-USB-3-0-Type-A-Male-to-Female-Connector-Extension-Cable-Adapter-Blue-/161377525870?pt=AU_Laptop_Accessories&hash=item2592d9a06e&_uhb=1)
USB 3 by definition can provide higher currents, so one would hope the cables have a decent wiring gauge.
Why are most USB cables one confusing and boring colour? It is better if they are different colours. Same with power cords, so you pull out the right one. Same with cars, but there are many fools around who prefer dangerous camouflaged coloured cars.
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Jakeypoo -
thanks for the info it's useful but when buying USB leads online they don't list
the conductor wire gauge.
vk3drb-
very good idea about USB 3 leads, unfortunately your links didnt work for me.
I am going to buy one of these 3M long-
http://www.ebay.co.uk/itm/400725406451?_trksid=p2055119.m1438.l2649&var=670269920472&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.co.uk/itm/400725406451?_trksid=p2055119.m1438.l2649&var=670269920472&ssPageName=STRK%3AMEBIDX%3AIT)
USB 3.0 EXTENSION CABLE Mainly Used In External Hard Drives,High-Resolution Webcam,
Video Monitor,VideoDisplay,Usb Interface Digital Camera,Digital Camera,Ray Drive,etc
100% Brand New
Supports data transfer speeds of up to 5Gbps—10 times faster than USB 2.0
This cable supports higher electrical currents to meet the greater electricaldemands of bus-powered USB 3.0 devices
Backwards compatible with USB 2.0 devices
Connector: USB3.0 Male to USB3.0 Female
Available Cable Lengths: 1, 1.5, 2, 2.5 & 3 Meter
Color: Blue
when it comes I will do a charge current test on it.
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A slightly different question - does anyone know where to get raw USB cable (on a reel) from?
It's tricky to find a search that works.
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for USB cable you need 4 conductors and an overall screen
search ebay for 4 core screened cable reel
and buy the best cable you can afford if you are going to make long runs
http://www.ebay.co.uk/sch/i.html?_odkw=4+core+screened+cable&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313&_nkw=4+core+screened+cable+reel&_sacat=0 (http://www.ebay.co.uk/sch/i.html?_odkw=4+core+screened+cable&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313&_nkw=4+core+screened+cable+reel&_sacat=0)
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It needs to be the right impedance (90 Ohm, iirc somewhat unusual), and the data pair should be screened, and the power pair should be thicker gauge... By the time yo meet that lot, you're looking at something specifically USB, I think.
For that project, I ended up butchering good USB cables, but that's a pain - not least because the annoying plated shield strands are very hard to solder.
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I have never seen USB cables like that
normally they are 4 of the same conductors
with an overall foil screen.
your's sound the proper way to do it though :-+
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this is quite interesting
http://voyager8.blogspot.co.uk/2013/04/how-to-choose-good-usb-data-and.html (http://voyager8.blogspot.co.uk/2013/04/how-to-choose-good-usb-data-and.html)
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A slightly different question - does anyone know where to get raw USB cable (on a reel) from?
It's tricky to find a search that works.
LCOMM Has bulk usb cable
Or use search term "bulk USB cable"
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Aha, thanks! Bulk was the word I couldn't guess.