USB current???
USB current???
(OP)
Hello to everybody,
it's the first thread i open here, and i hope you'll be able to help me...
I always knew that USB standard allows a current to be sinked of 500mA...great surprise today when i realized that connecting my HTC Tatoo to the Notebook USB port it sinked 780 mA...
Am i crazy? Is this normal? Shouldn't the USB port be limited to 500mA? Otherwise...what am i missing?
Thanks in advance for your helpfull answers..
Best regards,
Andrea
it's the first thread i open here, and i hope you'll be able to help me...
I always knew that USB standard allows a current to be sinked of 500mA...great surprise today when i realized that connecting my HTC Tatoo to the Notebook USB port it sinked 780 mA...
Am i crazy? Is this normal? Shouldn't the USB port be limited to 500mA? Otherwise...what am i missing?
Thanks in advance for your helpfull answers..
Best regards,
Andrea





RE: USB current???
Dan - Owner

http://www.Hi-TecDesigns.com
RE: USB current???
Thanks a lot.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: USB current???
It asks for it in units of 100ma in 2.0 and 150ma in 3.0(usb on the go)(Up to 5 units per device). I also think the max power can change depending on the communication speed.
RE: USB current???
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: USB current???
Under normal operating mode, the device must request how much current it wants to draw up to 500mA. Since the value used to communicate this is byte wide, each unit of specified current represents 2mA.
RE: USB current???
And many such sticks come with a 2-plug cable to draw power from 2 sockets if connected directly to older laptops that enforce the 500 mA limit.
Another older stick I used to have contained a battery to solve the peak power issue.
RE: USB current???
I'd like to recharge the battery of my HTC using the AUX input (actually a USB Socket)of my Ford Fiesta car , but i'm worried that HTC asking for more current than the standard one of USB may results in damaging the AUX input in my car...
Do you think the current would simple be limited by the USB (AUX) controller or that some damage may occur?
Thanks a lot again,
Andrea
RE: USB current???
I'm guessing the Fiesta's USB port can take care of itself.
There is an Automotive forum on this site you could try.
David Castor
www.cvoes.com
RE: USB current???
Dan - Owner

http://www.Hi-TecDesigns.com
RE: USB current???
USB ports will provide power to even the simplest device. A simple, completely mindless, USB-powered device can draw power from any common (USB 2.0) socket. Hand shaking is obviously optional.
In fact, some USB-powered toys have two wire (power only) cords, no data wires. There's even a USB-powered coffee cup warmer, nothing more than a 10 ohm, 2.5 watt resistor.
RE: USB current???
Dan - Owner

http://www.Hi-TecDesigns.com
RE: USB current???
uyou percetly took the point...I don't mind about the communication while charging the device...i just wanted to know what is the current limit of a USB host...
So do you all agree that it should be 1,5A when there is no communication? May you tell me if there is some official document on the internet saying this?
Thanks a lot to everybody for helping
Bye bye
Andrea
RE: USB current???
Apparently there is also a USB 3.0, but this is the first I have heard about it.
RE: USB current???
Not me. I've seen too many instances where the limit (for USB 2.0) was described as being "500 mA".
And I've seen several explicit exceptions where the product info states that the ports provide more than (again) "500 mA" - typically to support 3G Internet sticks.
But USB power ports, such as the little white power cube provided with iPhones, provides 1A.
It's a classic case of YMMV.
Have you checked the car's manual?
RE: USB current???
Noway, 3.0 ups the specs a bit, but only a few compliant devices have hit the shelves yet... I think only a single motherboard has been offered, and I've seen a handful of devices like hard drive docks, etc.
BTW, I just noticed this is not an engineering design, sounds like a home project... this thread may disappear soon.
Dan - Owner

http://www.Hi-TecDesigns.com
RE: USB current???
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: USB current???
Sorry but...what does RF stands for in this sentence? :)
RE: USB current???
I didn't for the reason you mentioned, but I wanted to warn in case someone did (as well as remind Andrea that this site is for practicing engineers and hobby projects as a first post can get you booted).
Dan - Owner

http://www.Hi-TecDesigns.com
RE: USB current???
I didn't for the reason you mentioned, but I wanted to warn in case someone did (as well as remind Andrea that this site is for practicing engineers and hobby projects as a first post can get you booted).
MacGivers...
Sorry but i don't understand what you mean...warning about what:)?
RE: USB current???
Not all USB products religiously follow "the spec", and current limits is one area where I've seen explicit mention of exactly that in the product manuals.
RE: USB current???
TTFN
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RE: USB current???
Dan - Owner

http://www.Hi-TecDesigns.com
RE: USB current???
Keith Cress
kcress - http://www.flaminsystems.com
RE: USB current???
RE: USB current???
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: USB current???
since i opened the thread i wanted all of you knowing how it finally ended...
In the user manual of the car there was no indication about the maximum current allowed for the USB device connected to the AUX input, so i tried and...luckly nothing exploded or went on fire...
Being like this i finally suppose that each manufacter put its own a limit to the maximum current allowed and, probably, the 500mA limit is, in the most of the case, valid just for the communication devices...for charging and similar the limit may vary from one manufacter to the others.
Hoping this thread may be helpfull for other people in the future, i thanks again all of you for your helpfull answers.
Best regards,
Andrea
RE: USB current???
http
John D
RE: USB current???
EngineerForum.Net
RE: USB current???
ht
RE: USB current???
Apparently when you plug the phone into the USB port of the PC, the charger wants to draw some serious current, at a level which is beyond the default capabilities of the USB port. This causes a warning message to pop up on the phone when it is connected to the PC. In order to make it work correctly, you need to run a little utility program that reconfigures the USB port to allow current draws of up to 1A. I wasn't aware that you could reprogram the USB ports to do this, but I thought of this post when I was trying things out.
Note: the Commercial Windows application that comes with the phone does this automatically. As a Linux enthusiast, I had to find an application and perform this function manually.