> From: Herb Peyerl <hpeyerl@beer.org>
>
> Todd Whitesel <toddpw@best.com>  wrote:
:::
>  > Also, I saw a mention of putting a toroid on the hard drive power when it
>  > comes into the shark from an external power supply. What's the recommended
>  > number of times to loop the wires around the toroid?
>
> I can tell you I'm powering 60 sharks off a single Sun3 VME chassis power
> supply and there's no 'toroids' within site of this baby... Just two 5 foot
> long solid copper bus-bars...

But you are talking about different things, right?  Todd wants to run 12
volts through the box into the drive, whereas you have connected 5v power
to a built-in connector, right? I would hope that there *IS* a filter
already on the 5v input.

If one just runs a wire through the case, then it conducts all the
internal noise outside to a nice EMI-radiating antenna, and perhaps more
problematically it conducts outside EMI, and this includes ESD events,
*into* your case.

It's not the end of the world, but an easy way to avoid this is to use a
lossy, EMC ferrite torroid. If you wind it so the net DC is zero (because
you have a return wire) then put as many turns on as fits, otherwise, "it
depends". You don't want to saturate your inductor with flux from the DC
component.

>  > What I'm hoping to do is put a (gutted) external SCSI drive case on top of
>  > the shark, with an IDE drive in it, and run both the IDE cable and shark
>  > power in through the back of the shark case.
>
> or you could just find a laptop disk and buy the little $12 converter.  I'm
> doing that on the shark that's going in my car...

Either should work. But in that case, don't bother with power supply filters,
unless you have two giant toroids for the IDE cable. :-)

	ross.harvey@computer.org