can you overcharge a usb port??(and damage stuff )

[soyeux28]

nothign happened to me!! its just prevention i havnt found a answer on google!!!


ok i bought a multiplier usb port (1 usb port become 4), and i was wondering (maybe i shoulda asked the question before buying lol) can you plug anything in it?  i mean can i plug my 2 u360 joystick, ipac and pacdrive in it whitout risking that everything explode?? or am i better using only 1 usb port per device!!?

thank you for the reply and the cp is really near completion   

[drventure]

Yes, you can certainly "overdrive" a usb port (i'm not sure I'd call it "overcharging" though).

The issue is one of milliamps.

A typical USB port can supply about 500 milliamps to whatever device it's plugged into. (that a rough approximation).

So if you have a 4port hub, that means you'll need at least 2amps to be able to fully power 4 connected devices. Now, realistically, most devices don't consume the full 500ma. But under load, they might get close or even go over.

A good example is an LEDWiz. The 32 port version can have 32 LED's connected. If each is drawing 20ma, that's 640ma total power if ALL LEDs were lit simultaneously. Considering that the LEDWiz consumes a small amount of power too, if you turn all the LED's on, you'll overdrive the usb port.

If you do that, nothing terribly serious will happen, no explosions or meltdowns, But you can almost be assured things won't work right. most likely, USB devices will start dropping offline, appearing like they've been unplugged, when they haven't. Or they'll start malfunctioning (I've had my IPac4 start emitting phantom keystrokes continuously for example.

So the key is
1) Get an idea of how much ma each device you'll connect might consume
2) add that up for a total ma current through the hub.
3) then check the hub's powersupply to make sure it can deliver more ma that what's consumed.

3a) if you're hub isn't powered (no external power supply) then it's drawing all it's power for the USB port it itself is connected to. That means that the hub, plus all the devices connected to it can consume no more than about 500ma, which is not alot to share among 4 devices (plus the hub).

Example, you've got 2 U360's, an IPAC, and a trackball

U360s take 150ma
Ipac=100ma
Trackball is 200 ma

total of 600ma, plus maybe 50ma for the hub itself means about 650ma. So it's likely if the hub isn't a powered hub, you'll have some problems.

But if it IS a powered hub, check the powersupply to make sure it can supply at least 600ma or so (about .6 amp). Most PS's will do that though will some really cheap hubs, you'll find woefully inadequate powersupplies.

For instance, a 7 port hub that comes with a 2amp powersupply will NOT be able to fully power all 7 devices connected to it (500ma*7=3500ma or 3.5amps).

I've found that Kensington, IGear and Belkin hubs seem to consistently provide powersupplies with their hubs that CAN fully power the max devices, but most of the cheaper hubs do not.

But again, most of the time, you shouldn't need to drive all connected devices at the maximum power level so you don't necessarily HAVE to have a PS able to do that. It's just a nice margin of safety.

[TopJimmyCooks]

Doc,
Do you know how much an opti-wiz (trackball and turbotwist attached) draws?  A usb dongle for microsoft wireless mouse/keyboard?  is there any reference out there or way to check/measure?  I just bought a steam powered multimeter I'm dying to try out!  .