Powered FireWire from PCMCIA?

Archived from groups: alt.comp.hardware,comp.sys.laptops (More info?)

t. wise wrote ...
> I have a Dell Latitude C640 laptop, and since it has no FireWire port, I
use
> a PCMCIA card. It does not, however, supply power to my new external
> FireWire drive as an internal FireWire port would.
>
> Does anyone know if it is possible to get a PCMCIA card that would supply
> power (as well as handle data) for an external FireWire drive? I would
love
> not having to tote around yet another power cord.

Possibly, but the amount of power available from the Cardbus port is
limited. The Belkin PC/USB2.0 card will supply power via USB but I have
been told that whilst it will drive a floppy drive it cannot supply enough
power for an external hard drive. (In that case an external power supply is
also provided that plugs into the PC card between the two USB ports). I
assume hat the same considerations will apply to firewire adapters.

I can't understand why no one has marketed such a converter that plugs into
both the PC and a USB port, driving data via the PC port whilst "stealing"
power from the USB. Certainly I have seen a USB hub that plugs into two USB
ports simultaneously in order to double the maximum available power.

David

Archived from groups: alt.comp.hardware,comp.sys.laptops (More info?)

"David Lee" <davidlee_malvern@dont.use.this.bit.hotmail.com> wrote in
message news:chhh88$br8$1@hamble.qinetiq.com...

> I can't understand why no one has marketed such a converter that plugs
into
> both the PC and a USB port, driving data via the PC port whilst "stealing"
> power from the USB. Certainly I have seen a USB hub that plugs into two
USB
> ports simultaneously in order to double the maximum available power.

What's needed is for notebooks to have an auxiliary 5 volt power jack for
powering external peripherals.

On one model of Tablet PC, one of the USB ports is able to supply more
power, and a special optical drive, sold by the manufacturer, is keyed with
an extra pin on the side, to only fit into the higher power USB port (which
has a hole next to it for the pin on the cable from the drive.

It would certainly be possible to parallel two or three USB ports to get
1-1.5A of current, but you have to somehow isolate the +5 from each port,
since each port is powered seperately. If you use diodes, you get a 0.7V
drop, which is unacceptable, but some LDO regulators might work.