Re: [CAD_CAM_EDM_DRO] Re: Power Supply Box's

Thanks Paul, I appreciate all the pointers I can get!

Jarrett

----- Original Message -----
From: "Paul Alciatore" <paulalci@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sunday, December 03, 2006 10:44 AM
Subject: [CAD_CAM_EDM_DRO] Re: Power Supply Box's


> Re: Your suggestion of a compartmented box. I see nothing wrong with
> this concept, but remember that only hindsight is 20:20. Problems
> have a way of popping up.
>
> I would make very sure that all of the box's components are very
> solidly connected electrically. RF equipment is constructed with
> bare metal contact and screws or other fasteners every inch or
> so. Computer chassis use sheet metal techniques that have tight
> fitting seams or fingers that pull the joint tight together. Modern
> computer equipment operates at frequencies that are in microwave
> range so you are designing an enclosure that would be usable for
> radars or communications equipment in that range. Microwave
> frequency energy can leak out of a crack that is less than 1/32" wide
> and less than inch long. Forget the 12 inches mentioned by someone
> above: microwaves radiate efficiently from antennae that are only a
> fraction of an inch long (1/4 to 1/2 wavelength). Critical
> components in such assemblies are often housed in separate cast metal
> boxes inside the overall enclosure and they are connected with
> shielded coax cables. These inner boxes are of cast construction for
> closer fitting seams and often silver plated "finger stock" is used
> around the entire length of the seam to ensure a good electronic seal.
>
> And also attach a good ground. Not the regular electrical green wire
> ground that is the same gauge as the power carrying wires, but one
> that is at least several gauges BIGGER. Keep it as short as possible
> and attach it to a regular ground rod (15 to 20 feet). Also route it
> as LOW as possible, preferable along the floor (a wire in the air is
> an antenna, not a ground).
>
> Another consideration, possible contradictory to the above, is
> cooling. You need adequate cooling for the electronics. Otherwise,
> you will be repairing/replacing on a regular basis. Components that
> generate the most heat are best located at the top, near an exhaust
> vent. The cooler components can be located below. FanS would be
> almost mandatory in an assembly like this and air flow around and
> THROUGH all the components should be carefully considered. All the
> openings, internal and external, should have metal screens to prevent
> radiation and chips from passing through. Filters on the air intakes
> may also be desirable to keep dust (abrasive) out. They need not be
> fancy, but they should be finer than normal HVAC filters. Foam or
> cloth could be used for fabricated filters. Or I am sure there are
> many commercial products.
>
> I probably forgot something.
>
>
>
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