>
> How well regulated is the +5v from using this method?  I would assume that
> this is a pretty "clean" supply, but since my application will be using
> ADC's I need a supply without a lot of ripples and what-not.  IIRC a
> previous post stated that the keyboard +5v line could source 120ma.  Is
> this correct?  I haven't calculated it all out, but my project should take
> 10-20ma max.

The amperage is fine. I wouldn't dare comment on the noise though as it is
the main +5 supply for the PC. From what I've read there usually is quite
a bit of noise on that particular supply, which is shared with the buses and
the disks. Which is why folks have suggested regulating the 12V supply instead
of using the 5V. Best bet is to take a scope to a few different PC's and see
how it looks.

>
> I really like this idea.  If the supply is clean enough I could make my DSO
> adapter box with the aforementioned 5 pin DIN connectors and a 25 pin
> connector for attaching a parallel cable and do away with the need for a 9v
> battery and regulator.

That's the idea. However if it turns out that the line isn't clean enough
you can always resort to the hybrid method where you supply the ADC from a
battery generated, regulated supply and power the rest from the keyboard. I
did exactly this for my programmer because I needed 13V which I regulate down
from 2x9V batteries. The 5V helps out because I use a consistently powered
5V circuit to control the batteries to eliminate drainage when not it use.

BAJ