Power USB hub from psu

**Peoples** · 03-14-2005, 04:25 PM

no problem with this, its pretty much common sense stuff here.......i'll be powering most of my components with an ITPS & snapon PSU that I never ended up using. But remember if you drop power on the hub and repower it while the PC is on, you might loose your devices

**DeltaFX** · 03-14-2005, 04:57 PM

A mobo's USB header only gives 500mA. That's enough for a passive HUB but if you plan to use devices like usb-powered Zip250, or a hungry webcam, it may not work, cause these devices needs each and every miliAmp.

A common 4-port externally powered USB2 hub need 5V & 2.2 A (4 x 0.5A + 0.2A for the hub itself). Powering the hub from a molex is the easiest way, because the 5v rail of a molex is produced by PWM, not linear regul, so no watt wasted in heat.

Add a relay to control the 5v line from a 12v fan header, and you'll be sure that all usb devices are off when pc is off.

Phidget has 4-port hub powered from 12v, iirc.

**stevieg** · 03-14-2005, 05:00 PM

Originally Posted by DeltaFX

A mobo's USB header only gives 500mA. That's enough for a passive HUB, but if you plan to use devices like usb-powered Zip250, or a hungry webcam, it may not work, cause these devices need all the 500mA.

A common 4-port externally powered USB2 hub need 5V & 2.2 A (4 x 0.5A + 0.2A for the hub itself). Powering the hub from a molex is the easiest way, because the 5v rail of a molex is produced by PWM, not linear regul, so no watt wasted in heat.

Add a relay to control the 5v line from a 12v fan header, and you'll be sure that all usb devices are off when pc is off.

Sounds right to me, only thing I would add is to ensure you use an inline fuse to be on the safe side.

**nsmoller** · 03-20-2005, 10:34 PM

if i want to power 2 usb hubs, could i use the 5v line or should i use the 12v... (or should i just get the f-ing 7 port hub

)

i need to power the hub and a full size dvd rom... i was thinking of making a make shift extension that plugs into a molex on the psu, the 5v wire goes to usb hub and the 12v goes to the dvd rom? they both should be grounded? which part of the 4 on the board needs to go to ground?