Date   : Thu, 13 Mar 2008 19:43:57 +0000 (GMT)
From   : info@... (Sprow)
Subject: Disc drive power

In article <A3D3DDD72D2B4A59870D742CD6C10438.MAI@...>,
   Ian Wolstenholme <bbcmailinglist@...> wrote:
> Just thinking out loud...
>
> Could a 3.5" disc drive be powered off a 9V battery?  Or a 5.25" drive?

As pointed out by others the voltage is only half the problem.
For reference the 3.5" floppy drives I sell for the BBC B are around 250mA
while the drive is being accessed and sub 30mA when idle.

So a 110mAh PP3 battery (with regulator to 5V) would last just over 3h doing
nothing or 30 minutes of drive access, assuming the cell voltage drops off
like a cliff face at the end of its life.

As you'd probably be using a linear regulator to get to 5V then the 4V
difference is doing nothing but heating the air - it'd be better to start at
a lower voltage (say 4AA) instead,
Sprow.