USB hubs - power requirements- questions about root hubs

I have a laptop with 3 USB ports. I prefer an external keyboard and
mouse and even DVD drive (externally powered). I use a laptop hard
drive in an external case for data transfer - this is powered by a
Y-cable. This requires a lot of unplugging/swapping ports, so I want
to get a USB Hub. I was googling about USB power requirements and
have looked at the power requirements for the connected devices in the
device manager. It seems that the mouse dongle uses 70 mA and the
keyboard dongle 100 mA. The drive seems to use only 2 mA - does this
sound right? Why would a mouse dongle need so much more than a drive,
and what is the purpose of the Y-cable if it uses so little? Also,
why do the root hubs say that they have 8 ports (which one of them
does) when there are only 3 ports altogether? One of the hubs says
that it has a mystery device attached - are some of the ports used
internally? I also have externally-powered external drives which I
might want to use. I was going to get a powered hub, but looking at
the things I'm hooking up, I'm thinking I might not need one? Can
anyone enlighten me? TIA.

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Hi Tia,

The required power requirements for anything is 5.2 Volts. A 4 port hub should power all your items. most of the time I have a Wireless mouse, 2 USB Sticks, 2 4 port hub and also some other items.

But what you need a hub will power everything.

Cheers,

Cohen

From: basilb4me
Sent: Sunday, October 14, 2007 3:48 PM
To: Computer_Help_and_Discussion%40yahoogroups.com">Computer_Help_and_Discussionyahoogroups.com
Subject: [CHAD] USB hubs - power requirements- questions about root hubs

I have a laptop with 3 USB ports. I prefer an external keyboard and
mouse and even DVD drive (externally powered). I use a laptop hard
drive in an external case for data transfer - this is powered by a
Y-cable. This requires a lot of unplugging/swapping ports, so I want
to get a USB Hub. I was googling about USB power requirements and
have looked at the power requirements for the connected devices in the
device manager. It seems that the mouse dongle uses 70 mA and the
keyboard dongle 100 mA. The drive seems to use only 2 mA - does this
sound right? Why would a mouse dongle need so much more than a drive,
and what is the purpose of the Y-cable if it uses so little? Also,
why do the root hubs say that they have 8 ports (which one of them
does) when there are only 3 ports altogether? One of the hubs says
that it has a mystery device attached - are some of the ports used
internally? I also have externally-powered external drives which I
might want to use. I was going to get a powered hub, but looking at
the things I'm hooking up, I'm thinking I might not need one? Can
anyone enlighten me? TIA.

Cheers,

Cohen
VK3FCLL

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