USB 5volt power

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

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

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

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

Regards 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

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.

I think if you cut the 5v traces to the usb port and connected them to the

- Mike

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

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

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

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.

No. no heating problem :)

Thanks ArameFarpado

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

Actually, if you're real careful, you can use a razor to remove the outer

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

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

petrus bitbyter wrote: Hi

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.

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. :)

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

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

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