USB 5volt power

[ArameFarpado]

hi all

i have a situation with USB ports that drop down the 5volt power in pins
1 & 4, when this appens, all devices connected shuts down.
(funcking VIA controllers)
i was hopping to solve this without spending more money (this is a bad luck
computer that allready had to replace a lot of components and belongs to a
family with low resources). I've read about one possible solution that goes
by installing a "self-powered USB-HUB" but it costs ¤ and i'm not sure that
will solve the problem.
so... i was thinking about desconect the 5 volts pins on the usb port (those
that come from the controller) and connect 5volt directly from the main
power unit, but i don't know if this is a good idea... will the controller
still recognize devices attached and put then to work? or the controller
needs to detect some mA on the power lines to detect devices?

Does anybody allready tried this?

Advices please.

Many thanks
ArameFarpado

 

[John]

hi all

i have a situation with USB ports that drop down the 5volt power in pins
1 & 4, when this appens, all devices connected shuts down.
(funcking VIA controllers)
i was hopping to solve this without spending more money (this is a bad luck
computer that allready had to replace a lot of components and belongs to a
family with low resources). I've read about one possible solution that goes
by installing a "self-powered USB-HUB" but it costs € and i'm not sure that
will solve the problem.
so... i was thinking about desconect the 5 volts pins on the usb port (those
that come from the controller) and connect 5volt directly from the main
power unit, but i don't know if this is a good idea... will the controller
still recognize devices attached and put then to work? or the controller
needs to detect some mA on the power lines to detect devices?

Does anybody allready tried this?

Advices please.

Many thanks
ArameFarpado

There are 2 per-port limits on the power available from a USB port.
One limit for devices that don't tell the USB controller how much
power they need and another limit for devices that do specify their
loading. If a device draws more than the first limit and does not
tell the controller, you may encounter problems. If a device
specifies it's current requirements but exceeds that specification,
you may encounter problems.

There is also a maximum total current limit for the particular USB
controller being used. If that total current limit is exceeded, the
chip will (usually) shut down. This sounds like the problem you are
describing. There are two solutions - connect fewer devices at one
time (example: printer and scanner not usually in use simultaneously)
or add an external powered hub.

John

 

[ArameFarpado]

John wrote:
Hi, thanks for you reply

There are 2 per-port limits on the power available from a USB port.
One limit for devices that don't tell the USB controller how much
power they need and another limit for devices that do specify their
loading. If a device draws more than the first limit and does not
tell the controller, you may encounter problems. If a device
specifies it's current requirements but exceeds that specification,
you may encounter problems.

There is also a maximum total current limit for the particular USB
controller being used. If that total current limit is exceeded, the
chip will (usually) shut down. This sounds like the problem you are
describing. There are two solutions - connect fewer devices at one
time (example: printer and scanner not usually in use simultaneously)
or add an external powered hub.

John

This problem appens with a usb-adsl modem, the modem have been replaced 2
times (3rd modem allready) and did not solve the problem, the adsl
connection is a high-speed and the power goes down when the modem starts to
work harder like when doing a download... it appens with just the modem
connected.

So, do you think that connecting the modem with a diferent 5volt supply and
desconnecting the 5volt supplied by the controller is a bad idea ?

Thanks
ArameFarpado

 

[Stanislaw Flatto]

hi all

i have a situation with USB ports that drop down the 5volt power in pins
1 & 4, when this appens, all devices connected shuts down.
(funcking VIA controllers)
i was hopping to solve this without spending more money (this is a bad luck
computer that allready had to replace a lot of components and belongs to a
family with low resources). I've read about one possible solution that goes
by installing a "self-powered USB-HUB" but it costs ¤ and i'm not sure that
will solve the problem.
so... i was thinking about desconect the 5 volts pins on the usb port (those
that come from the controller) and connect 5volt directly from the main
power unit, but i don't know if this is a good idea... will the controller
still recognize devices attached and put then to work? or the controller
needs to detect some mA on the power lines to detect devices?

Does anybody allready tried this?

Advices please.

Many thanks
ArameFarpado

From experience, but it takes time and failures, DON'T, repeat DON'T
assemble a system in which warious parts rely on other parts for power
supply. It "maybe" a nice advertising that it "works on USB" power, till
it stops!

Have fun

Stanislaw
Slack user from Ulladulla

 

[ArameFarpado]

From experience, but it takes time and failures, DON'T, repeat DON'T
assemble a system in which warious parts rely on other parts for power
supply. It "maybe" a nice advertising that it "works on USB" power, till
it stops!

LOL, that's a good advise.
It's just that i don't "create" USB devices

Regards
ArameFarpado

 

[John]

John wrote:
Hi, thanks for you reply


This problem appens with a usb-adsl modem, the modem have been replaced 2
times (3rd modem allready) and did not solve the problem, the adsl
connection is a high-speed and the power goes down when the modem starts to
work harder like when doing a download... it appens with just the modem
connected.

So, do you think that connecting the modem with a diferent 5volt supply and
desconnecting the 5volt supplied by the controller is a bad idea ?

Thanks
ArameFarpado

Unless you already have the external 5 volt supply, I would suggest
getting an inexpensive powered USB hub. Most of the USB 1.1 hubs are
discounted now because people want USB 2. However, the USB 1.1 speed
is more than adequate for DSL data speeds.

John

 

[James Thompson]

hi all

i have a situation with USB ports that drop down the 5volt power in pins
1 & 4, when this appens, all devices connected shuts down.
(funcking VIA controllers)
i was hopping to solve this without spending more money (this is a bad
luck
computer that allready had to replace a lot of components and belongs to a
family with low resources). I've read about one possible solution that
goes
by installing a "self-powered USB-HUB" but it costs ¤ and i'm not sure
that
will solve the problem.
so... i was thinking about desconect the 5 volts pins on the usb port
(those
that come from the controller) and connect 5volt directly from the main
power unit, but i don't know if this is a good idea... will the controller
still recognize devices attached and put then to work? or the controller
needs to detect some mA on the power lines to detect devices?

Does anybody allready tried this?

Advices please.

Many thanks
ArameFarpado

If you are talking about cutting connections on the main board, then not
good idea. But if you are talking about using a cable with a junction box
(like a usb hub), then I see no problem - but don't rely on my say so as I
am no expert. As I understand the usb works similar to Ethernet as the
device signals its presents, and not that there was a current change.
Does the modem they have not have its own wall transformer? My DSL modem
has Ethernet or usb and its own power supply. Maybe also a cooling problem
with the mainboard chipset? Do they run there system inside a desk
compartment? If so they may need to mount a fan on the compartment to bring
in cool air etc.

 

[Michael Kennedy]

I think if you cut the 5v traces to the usb port and connected them to the
5v from the psu it would work fine. I can't see why that would be a problem
and if it doesn't work correctly for some reason you could always just hook
it back up the way it was or just plug a usb hub into it (they don't use the
5v).

- Mike

 

[ArameFarpado]

I think if you cut the 5v traces to the usb port and connected them to the
5v from the psu it would work fine. I can't see why that would be a
problem and if it doesn't work correctly for some reason you could always
just hook it back up the way it was or just plug a usb hub into it (they
don't use the 5v).

I'll try that soon, thanks

ArameFarpado

 

[jakdedert]

I'll try that soon, thanks

ArameFarpado

Before I went cutting any traces on the computer, I think I'd buy a USB
extension cable, cut it in half ond rewire everything BUT the 5v line.
Leave the computer side of that hanging (insulated) and hook the other
end to your 5v, wire a return from the ps and you're done.

jak

 

[ArameFarpado]

If you are talking about cutting connections on the main board, then not
good idea.

not in the motherboard, in a PCI USB controller... pins are easy to access.
the usb onboard controller is long gone death.

But if you are talking about using a cable with a junction box
(like a usb hub), then I see no problem - but don't rely on my say so as I
am no expert. As I understand the usb works similar to Ethernet as the
device signals its presents, and not that there was a current change.
Does the modem they have not have its own wall transformer?

no, it it have just the USB cable and the phone cable (rj11)

My DSL modem
has Ethernet or usb and its own power supply.

Yeah, but those modems costs, and over here ISPs are offering this shit
modems to grab new clients.
I've told then that the best is to get a adsl-ethernet modem and a ethernet
card, but they are not happy with the idea, sinde the computer allready had
to replace the USB controller and the hard-disk.

Maybe also a cooling
problem
with the mainboard chipset? Do they run there system inside a desk
compartment? If so they may need to mount a fan on the compartment to
bring in cool air etc.

No. no heating problem

Thanks
ArameFarpado

 

[ArameFarpado]

Before I went cutting any traces on the computer, I think I'd buy a USB
extension cable, cut it in half ond rewire everything BUT the 5v line.
Leave the computer side of that hanging (insulated) and hook the other
end to your 5v, wire a return from the ps and you're done.

jak

There is a frontal port, one that have an internal cable with separated
terminals for each pin...
i'll do the testing on those pins first, don't worry

Thanks
ArameFarpado

 

[JW]

Before I went cutting any traces on the computer, I think I'd buy a USB
extension cable, cut it in half ond rewire everything BUT the 5v line.

Actually, if you're real careful, you can use a razor to remove the outer
2" of insulator, then just cut the 5V line.

 

[petrus bitbyter]

John wrote:
Hi, thanks for you reply


This problem appens with a usb-adsl modem, the modem have been replaced 2
times (3rd modem allready) and did not solve the problem, the adsl
connection is a high-speed and the power goes down when the modem starts
to
work harder like when doing a download... it appens with just the modem
connected.

So, do you think that connecting the modem with a diferent 5volt supply
and
desconnecting the 5volt supplied by the controller is a bad idea ?

Thanks
ArameFarpado

According to the specifications a USB-device can use up to 100mA when
connected and up to 500mA after negotiation... When the host can provide it.
If not or when the device exceeds the agreed current, the host may shut down
the link.

On the low side some hosts can provide only 100mA, so they can power only
one one or more low power devices as long as they together use less then
100mA. Notebooks, some Toshiba's for instance, are known for it. On the high
side I ever got a MB which had it's 5V directly connected to the 5V pin of
the USB port. Even no fuse!

As far as a host is concerned it does not need to power a USB device.
Printers, scanners and the like often have their own power supply. I have a
USB-hub that can be powered via the host or externally. Originally the
choice has to be made by a switch, but that switch was replaced by a 1N5819
Schottky diode.

USB-ADSL modems are too well known for their poor performance. Some of them
work flawlessly for years but a big bunch of them did not and was replaced
by ethernet modems. Over here that USB-ADSL things are not used by ISPs
anymore. (That's to say the ones I met so far.)

So I don't expect problems when you give that modem it's own 5V power supply
and disconnect the USB power line. The USB connectors are designed to make
ground contact first, then power and then signals. Maybe the modem has an
external power connector or was ever prepared for it. You may find out when
you open it.

BTW It might have helped to mention the brand and type of that
USB-ADSL-thing.

petrus bitbyter

 

[ArameFarpado]

petrus bitbyter wrote:
Hi

As far as a host is concerned it does not need to power a USB device.
Printers, scanners and the like often have their own power supply. I have
a USB-hub that can be powered via the host or externally. Originally the
choice has to be made by a switch, but that switch was replaced by a
1N5819 Schottky diode.

Oh, this puts all my doubts away... that HUB can be powered by the
controller or it's own power supply, so it doesn't matter who is powering
up.

USB-ADSL modems are too well known for their poor performance. Some of
them work flawlessly for years but a big bunch of them did not and was
replaced by ethernet modems. Over here that USB-ADSL things are not used
by ISPs anymore. (That's to say the ones I met so far.)

Here in Portugal, most ISPs offer these crap modems to grap clients, even to
high speed connections like 4Mbit and 8Mbit.
It is also a bit dificult to put them running on Linux... but they still
believe that everybody must run windows... when somebody calls the ISP's
tecnical assistence and tell then that uses Linux, they allmost pist their
paints.

So I don't expect problems when you give that modem it's own 5V power
supply and disconnect the USB power line. The USB connectors are designed
to make ground contact first, then power and then signals.

The main power unit of the pc as a very well estabilized 5volt output (black
and red wires)... i'll connect to then.

Maybe the modem
has an external power connector or was ever prepared for it. You may find
out when you open it.

maybe... don't know if i going to open the modem... warranty reasons.

BTW It might have helped to mention the brand and type of that
USB-ADSL-thing.

It's those Alcatel (Thomson printed on them) SpeedTouch 300 Rev4
(the gray ones)
I've seen these modems work fine in low speed connections like 512Kbit/s,
this is the first time i setup a 4Mbit/s connection whit this kind of modem
and also the first time i see the modem "fall of the horse".
I believe in this case that the prime guilty part is the VIA USB
controller... this chips VIA are known to be problematic.

Many thanks
ArameFarpado