[eagle] Re: Still Even Another Revision

Chuck Green greencl at mindspring.com
Thu Oct 18 13:51:23 PDT 2007


Hi Dick,

Given this design (no access without removing the module), I like it
better and better. I still have one *big* concern and that's the center
mounting screw for the front plate. The intrusion of the base plate into
the PCB area to accommodate this screw bothers me a lot. You point out
that it does not touch the PCB but it definitely precludes a connector
at this location which I see as a severe limitation on the connector
area of the front plate. I just measured a right angle flight Sub-D
connector and its pins protrude through the bottom of the PCB almost
1.5mm. I also measured a right angle SMA connector and its pins protrude
through the bottom of the PCB almost 2.5mm. I hope you can do something
about this. I fear that the connector plate area usefulness may have
actually been degraded from the original design.

Can you give us a view that shows the inside of the base plate directly
behind the front plate?

I'm looking forward to a dimensioned drawing. I suspect I'll have more
comments then.

Rick's suggestion of a base plate that includes the sides, back, and (I
would add) possibly the front gives us something like the modules for
AO-51. It probably would be stiffer, although I suspect the base you
have just designed is stiff enough (although you might be able to make
the base plate lighter if the sides/back/front were integral). I doubt
there is any advantage to being able to insert the PCB from the front
due to clearances within the satellite but you can evaluate that better
than I. It would give module builders the opportunity to secure heat
producing parts such as TO-220's directly to the walls (I did this quite
a bit for P3D modules I built). I know that these can be tricky to
machine due to the flexing of the walls if they get too thin. My $0.02
worth.

Chuck



Dick Jansson-rr wrote:
>
> Bob:
>
> Owing to the “popularity” of these discussion, I have done further 
> revisions of the E05 20 Module. It is now officially termed a 
> “140x180” module as the PCB has grown to that size. The size increase 
> has allowed an increase in PCB working area to a clear 126x173.6mm, 
> 6.35mm deep, save for three protrusions – two support posts and the 
> third at the front to accommodate the third connector plate screw 
> (this later post is not in contact with the PCB as explained earlier). 
> The three attached PDF files show the module with its cover attached, 
> cover removed and PCB and cover removed.
>
> I shall shortly be able to issue a drawing of this revised PCB.
>
> The cover has further been simplified as the rear mounting flange has 
> been removed and replaced by side-inserted screws, as is for the 
> cover’s sides.
>
> Chuck has properly noted that such a mounting of the PCB will enhance 
> the thermal characteristics of the PCB. I plan to combine an earlier 
> PCB thermal analysis and this new PCB configuration and expect to be 
> able to identify the power handling capability of this PCB without the 
> use of any added heat sinks. The enhancement should certainly be 
> available along three sides of the PCB. That data should be available 
> for the Symposium.
>
> Dick Jansson, KD1K
>
> kd1k at amsat.org <mailto:kd1k at amsat.org>
>
> kd1k at arrl.net <mailto:kd1k at arrl.net>
>
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