Re: [Xylo-SDR] Questions - Enclosure - MB - Kicad

["Eric Ellison" <ecellison@comcast.net>]

Lyle

Thanks. 

Yes, had considered most of this and all your points are well taken. If the
group goes with this enclosure I will upfront the purchase of (N) enclosures
and supply everyone. This is not a Digi-Key part! I'll definitely get
samples or buy a sample run at $100 to make physical measurements. (I'm in
the Wood Industry and a 2x4 varies considerably!)

The motherboard should be designed along slots (.75 inch max component
height plus a scooch) and also allow for one slot for an inexpensive copper
clad board shield between boards at the length we choose. (EMI suppressors)

I still like the standoff mount from the backplate. We really don't want the
buss to be exposed or covered with ????. Plus we can get to sub mm
adjustment with a standoff arrangement. The MB should NOT take up the full
width of the 6" enclosure since we want to feed power and components into
the left or right justified motherboard.

One end of the MB circuit board, which we have decided should be passive,
should be for jump connections to the power supplies and have Berg
connectors for power indicator leds.

We can make an el cheapo 4x4 Single sided board for power, on/off switches
etc, which need front panel access but not buss accessibility.

Eric









-----Original Message-----
From: xylo-sdr-bounces@lists.ae5k.us [mailto:xylo-sdr-bounces@lists.ae5k.us]
On Behalf Of Lyle Johnson
Sent: Saturday, January 14, 2006 1:39 PM
To: Xylo-SDR Discussion
Subject: Re: [Xylo-SDR] Questions - Enclosure - MB - Kicad

> I therefore propose that we increase the proposed project card size from
2x4
> to 4x4 which is a 'happy medium' which Phil suggests below. This also
allows
> for Phil - VK6APH BPF board, A Jupiter GPS receiver etc. For 'Dead Bug'
> expeimenters like Bill - KD5TFD, he could use a 4x6 full length card and
> have 2" sticking out the front for experimenting without a card extender.
It
> also allows us to get on with Motherboard design with a maximum vertical
> dimension of 96 mm. (case height between lands). I propose the motherboard
> height dimension be the the size of the 96 pin mating connector (3.7").
The
> holes in the connector will mate with standoffs for rigidity.
> 
> I think a 4x6x4 enclosure would make a cute little radio!

I think that the ability to put the connectors, controls, etc. on the 
PCB is a huge benefit for repeatability and reliability of whatever this 
group builds.

You might want to consider designing the "motherboard" to accommodate 
the card spacing dictated by the slot spacing in this extrusion, then 
build a motherboard and at least one board of the proposed dimension, 
preferably with one or more PCB-mounted connectors or controls.

Next, measure the extrusion length required based on the stackup, 
including the mounting arrangement for the motherboard, to be sure you 
get the length of the extrusion exactly right. You don't want it to be 
too short, and you don't want a lot of "slop".  Consider how the cards 
will be retained in the mechanical system design.

Then, order some extrusions cut to the known-accurate length, allowing 
for the tolerance of the cutting operation.

I won't mention how many times I've been bitten by not measuring, only 
calculating, an enclosure size.

Another thought: the motherboard could be sized such that its PC board 
forms the backplate of the enclosure.  Downside is exposed connector 
tails -- or maybe that is a plus for having exposed test points?

73,

Lyle KK7P

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