Mr Whippy
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| posted on 18/9/12 at 02:55 PM |
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USB are they all the same voltage?
I have several USB things like camera's, Ipods etc that all charge on the computer through the USB ports.
If I was to use a wall or car charger with a USB output, does it matter at all about what you are charging. I'd have thought they were all
5v?
My new camera's car charger is £30! what the feck? how can if be any different to my other ones?!
[Edited on 18/9/12 by Mr Whippy]
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tegwin
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| posted on 18/9/12 at 03:04 PM |
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Not all USB ports are capable of giving high current (so hard disks and other heavy drain stuff) quite often wont work on unpowered USB hubs or some
laptops with low power ports.
Also some hardware has to actually "talk" to the computer whilst charging. They dont accept a charge without this communication. Their
expensive chargers presumably emulate this handshake to initiate the charge cycle.
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Mr Whippy
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| posted on 18/9/12 at 03:16 PM |
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ah I didn't know that, though in my case I think it is just charging a battery
Thanks
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ReMan
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| posted on 18/9/12 at 03:32 PM |
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Yes all 5v
But various specs. The WIKI is pretty good for USB
www.plusnine.co.uk
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SteveWalker
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| posted on 18/9/12 at 05:55 PM |
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IIRC they are all 5V. The spec calls for 100mA, but the device can ask for more current and obtain 500mA - only one device at a time can have the
higher current. However, most modern PCs have more than enough power and don't bother with this, just allowing up the 500mA by default - I would
assume most chargers are similar.
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vanepico
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| posted on 18/9/12 at 06:25 PM |
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If they need more power, they normally just have two usb heads on the end to go into two ports, this doubles the amount of current they can get. I got
a cheap 2.5" drive caddy from ebay and it had this.
__________________________
Will CAD for food/money/beer...
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Paul_C
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| posted on 18/9/12 at 08:42 PM |
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The Car Charger might be a High Current charger which I think can deliver around 1.5 A. The Charger is signalled that the USB 'load' can
take it by shorting the signals D+ and D-.
Standard USB loads are meant to negotiate with the host to check that thay can take 500 mA. But typically with computers / software / consumer stuff
proper specifications tend to get ignored. The innocent Customer then wonders why things don't work as expected.
If you have many hours to kill USB.org covers it all.
£ 30 isn't too bad if it's done properly and doesn't sell in high volume. There used to be a lot of CE marked Mobile Phone Chargers
that would fail EMC tests such as automotive transients and the like that it would be unwise to use with an expensive phone. There is a lot of rubbish
around.
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nick205
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| posted on 18/9/12 at 08:59 PM |
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USB specification provides for +5Vdc and up to 0.5A per port. Bus powered hubs (i.e. those powered from the host USB port they're connected to)
are limited to 100mA per port (usually up to 4 ports + 100mA for the hub electronics itself). Some hubds cheat the spec and don't limit to
100mA per port, but still have the same overall limit. We've developed several devices with integrated hubs to run multiple devices in a single
box and designed our own hub circuitry and firmware to allow this to happen safely.
Cheapy devices we've tested at work don't always deliver the full 500mA, but not far off. Most car chargers we've seen easily
deliver the 500mA to specification.
As mentioned above some more elaborate devices communicate with the USB host in order to allow charging. These require the more costly OEM charger
from the equipment manufacturer. Most phones do not employ this feature (no idea on iPhones mind) so as to allow flexible charging; mains, in-car,
computer etc.
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mcerd1
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| posted on 18/9/12 at 09:16 PM |
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quote:
Originally posted by tegwinAlso some hardware has to actually "talk" to the computer whilst charging. They dont accept a
charge without this communication. Their expensive chargers presumably emulate this handshake to initiate the charge cycle.
do you think that could that include an old(ish) nokia N86 ?
had a few issues getting it to carge of certain USB ports...
-
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coyoteboy
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| posted on 18/9/12 at 10:05 PM |
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Yep, the high current request has been around from very early on and to charge a mobile (Even an anchient one) from 100mA would take some time
(8hrs+).
[Edited on 18/9/12 by coyoteboy]
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Toltec
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| posted on 18/9/12 at 10:27 PM |
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If you want to run a phone as a sat nav you may need more than 500ma, I found that on a 500ma supply my phone slowly discharges the battery. A 1A
supply is fine and will even charge the phone.
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Agriv8
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| posted on 19/9/12 at 06:55 AM |
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I have a 1amp 12v one for thae car that seems to charge most things. I have a Generic usb 240V plug in wall chager for phones ect and works for
everything apart from :-
IPad2
Nikon s8000 camera.
ATB Agriv8
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
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