Subject: Re: shark power supply questions
To: Todd Whitesel <toddpw@best.com>
From: Todd Whitesel <toddpw@best.com>
List: port-arm32
Date: 10/05/1999 02:20:03
Score! The shark is alive. It comes up with a black-on-white-block text
screen; while I wonder what "probe-scsi" is doing in the firmware, it
looks good.  Memory is 32 megs.

Will this sucker boot from an ATAPI CD ROM drive? All my ATAPI Zip's are
inside ATX cases of running machines right now.

Herb>Make sure you pick the 5V line off the power connector... 12 volts would
Herb>surely be a bad idea.

I used a power adaptor left over from my internal SCSI Zip drive that only
had the 5V and one ground wire in it. Works great.

Herb>"remote"?

Yeah, it looks like a TV remote with web-browser buttons and simple playback
controls, I guess for watching video streams.

Herb>or you could just find a laptop disk and buy the little $12 converter. I'm
Herb>doing that on the shark that's going in my car...

Somehow I don't get good vibes from the idea of mounting a bracket inside the
case when it wasn't designed for it. If I had been even luckier and got a zip
disk model, then I might try it.

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

Yeah, I'm not happy about that part either. Would it help if I wrapped
aluminum foil around the cables and secured that to the chassis openings?

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

Translation, I need a bit more of a EE degree to figure it out myself.

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

Um, yeah. Part of the reason I'm doing it this way is to avoid using the
5V "barrel" power connector on the shark which has no power switch on it.
The little seagate disk enclosure that I'm running power from (and IDE
cable to) has a real power switch.

Todd Whitesel
toddpw @ best.com