[eagle] Re: CAN-Do Suggestions from Juan

Dick Jansson-rr rjansson at cfl.rr.com
Thu Jul 19 05:03:36 PDT 2007


The module design has been done with these forces in mind. The designer has
been through the hoops associated with operating in this environment.

Dick Jansson, KD1K
kd1k at amsat.org 
kd1k at arrl.net 

-----Original Message-----
From: eagle-bounces at amsat.org [mailto:eagle-bounces at amsat.org] On Behalf Of
Lee McLamb
Sent: Thursday, 19 July, 2007 02.57
To: eagle at amsat.org
Cc: David Smith; Dave Black ((Work)); Dave Black ((Home)); Samsonoff at Mac.
Com; Juan.Rivera ((Work))
Subject: [eagle] Re: CAN-Do Suggestions from Juan

As we consider flex stresses we also need to ensure we've considered the 
launch adapter specs for G-forces and are providing adequate support for the

boards.

For ESPA:  10.6 G on all axis 
For ASAP5:
X  +/- 6 g
Y  +/- 6 g
Z  -7.5 g / +5.5 g

Lee-KU4OS

On Wednesday 18 July 2007 08:41:23 Robert Davis wrote:
> Jim, Juan, and all,
> I'm sorry for not being active in this conversation earlier. I'm
absolutely
> creamed at work. I forecast being at my maximum at work for about another
> week or two. I'll spare you the details.
> I am sure that we can redesign a module that is at least partially milled,
> that will maintain the flatness that Juan quotes from a vendor of .008"
per
> 1". It really isn't that hard, but absolutely throws out the sheetmetal
> baseplate we've had until now. In my mind, for this one issue it's only a
> decision as to whether the entire module height is milled (and then
there's
> just a simple flat cover) or whether the milled portion is part of the
> height of a module and a shorter "bent cover" is used. I think I'm
favoring
> a milled module with simple flat cover.
> For the issue of the isolation of the CAN-DO in a separate compartment,
> this can be done and I guess I've seen it frequently with milled modules.
> I'd like to avoid it because it moves farther towards having truly
> customized modules, instead of a generic with minor connector or heatsink
> mods. For the issue of the RF connectors exiting the side of the module,
> this is potentially a larger issue. In our current arrangement, we have
> identified a connector face on the modules because all the modules are
> (potentially) packed side-by-side to consume a dimension of the
spacecraft.
> If we had an accurate accounting of how many modules, and what sizes they
> are, then we might be able to say with confidence what gap is present
> between modules available for RF connections. I've attached a spreadsheet
> with the only accounting of modules that we've attempted and it's pretty
> old.
> The flip side of this would be: impose a requirement on mechanical to
> provide room for RF connectors on specific (or all) modules, and specify
> what the module sizes are and we can see where we stand. Maybe it would
> help to have an idea of what kind of protrusion from the side of a module
> we're talking about. 20mm?
> So, comments on the list of modules & sizes can get us started with
> determining what is available next to a module for RF.
> bob
> Robert Davis
> KF4KSS
>
> On 7/17/07, Jim Sanford <wb4gcs at amsat.org> wrote:
> > Team:
> > Some comments on this thread, as I indicated earlier.
> >
> > In no particular order:
> >
> > " . . working in a vacuum."  To not do so is why we have EaglePedia, and
> > why I have been pushing for requirements and sharing of lessons learned.
> > The harsh reality is that Juan and his team have been testing some of
our
> > stuff in new ways, and we're learning things.  Perhaps we could/should
> > have learned some of these things in the past, I don't know.  We didn't,
> > but we know them now, so let's press ahead.
> >
> > Regarding the board flexing issue:  Juan, please add this to your
lessons
> > learned.  It would be a welcome addition to the component selection talk
> > that Lyle gave at Pittsburgh.  In the mean time, please extract all the
> > things that you've learned we should do differently into a text document
> > that I can add to the lessons learned sub page from my project
management
> > page.  I'll get Dave to post, this is all good stuff.
> >
> > Milled enclosure:  Bob Davis is looking into that.  I've asked Dick
> > Jansson to locate an unmodified sheet metal enclosure to get into Juan's
> > hands for evaluation.  Many considerations here, let's make decisions
> > based on EVALUATION.
> >
> > EMI:  We need requirements, but nobody has stepped up to write or
> > extract.  My threat (grin) to dig out the MIL-SPEC was properly
> > incinerated.  So, we still have no requirements.  I offer the following
> > "top level" EMI requirements, based on my earlier post regarding the 3
> > things it takes to have EMI:
> >     1.  Every potential EMI source (like switching power supplies)
should
> > be as quiet and well shielded as reasonably posible.
> >     2.  Every potential EMI victim should be as immune to conducted and
> > radiated (other than on-channel thru the antenna) as reasonably possible
> > I'll leave it to guys like Tom Clark to tell me what exponent we should
> > attach to the value of this in the aggregate of many sources and
victims,
> > I just know that attention to the basics on a per module basis will make
> > our lives much easier at integration/testing time.
> >
> > We also need to standardize on IF output levels from RX modules and
input
> > levels from SDX to TX modules.  Volunteers?
> >
> > I think the above provides all the guidance we need to proceed with an
> > electrical redesign of the U RX based on what we've learned so far. 
> > We'll need Bob's input on housing studies and we'll need to assess what
> > the CAN-Do! team is up to before committing to PCboard layout and
> > construction. Juan thinks we should wait until some top-level specs are
> > better refined; we'll come through this discussion.
> >
> > Regarding the CAN-Do widgets:  The team has offered to do a redesign. 
> > I'm reluctant to get too carried away on this.  We've learned some
things
> > that we'd like to change regarding the power supply, but the rest of it
> > works, and we should not toss that.  So, this is an area where I very
> > strongly feel that incremental improvement is in order, not a wholesale
> > redesign.  My sense is that the power supply noise issues we've
> > discovered IN TESTING were not anticipated by design folks who are not
> > necessarily power supply experts.  (Bdale just confirmed this on the
> > phone.)  Now that we have them, we're seeking such experts.  We may get
> > some input soon from someone who is such an expert who knows somebody
who
> > knows somebody who is on the team.  If any of the rest of you have such
> > expertise or know somebody who has it, please step up to the plate.  I'm
> > gratified at the willingness of the CAN-Do! team to do whatever it
takes,
> > but DO NOT want to toss the baby with the bath water -- we then start
> > over, and cannot afford that in time, intellectual effort, or $$  Part
of
> > this discussion is the recent conversation regarding high density
> > connectors.  If we need them and they're acceptable, so be it.  Some
seem
> > to think this is a big deal, I do not -- it's a technical issue to be
> > evaluated and dealt with.
> >
> > One commentor expressed disappointment about silence regarding these
> > changes and lack of direction from "management".  I have been following
> > this conversation closely, but have not weighed in since I had no new
> > thoughts or extraordinary value to add.  Rest assured, I follow these
> > issues closely, and try not to weigh in unless I have something
> > significant to say.  My silence to this point should be interpreted as
> > satisfaction with the conversation and apparent direction.  If ever you
> > think I should weigh in and am not, ask the explicit question.
> >
> > Chuck asked if someone would pursue alternative inductor components to
> > reduce radiated noise.  I have asked Juan to see of Project Oscar would
> > take this on.  I think there is tremendous value in testing with
> > substitues of this single component.
> >
> > Finally:  SYMPOSIUM
> > It is CRITICALLY important that we demonstrate something this year.  We
> > need it to dispel doubts and we need it to encourage fund-raising.  Our
> > hosts, the Wireless Association fo the South Hills (WASH) have committed
> > to helping us do this.  They will provide a 30+ foot tower on a trailer,
> > antennas, coax, and I'll provide a power supply.  We have a working
> > U-band RX, and may have a better one.  Bob McGwier assures me that we'll
> > have a working SDX to demonstrate.  I'll get a 2m TX for it to drive at
> > significant power.  This will allow us to demonstrate Eagle in the hotel
> > and in the surrounding area -- vital for publicity and fundraising.  We
> > also need to show IHU and CAN-Do!, ifthey're working and sending
> > telemetry on the "downlink", so much the better!
> >
> > We have much to do in a few short months.  Let's get on with it.
> >
> > Thanks & 73,
> > Jim
> > wb4gcs at amsat.org
> >
> >
> >
> >
> >
> > Juan Rivera wrote:
> >
> >  Chuck,
> >
> > Forgive this long email...
> >
> > SInce everything is interrelated the only way to deal with it is from a
> > system engineering perspective (in my opinion).  You can't design the
> > various subsystems with each group working in a vacuum.  If you do, this
> > is what happens.
> >
> > For example:  I've researched the maximum amount of bending that should
> > be allowed on a SMT circuit board.  AVX, the capacitor manufacturer,
> > suggests a maximum bend radius spec for SMT circuit boards of 60 inches.

> > That works out to 0.0084" maximum deflection over any 1" segment.
That's
> > about the thickness of three sheets of paper.   The tolerances of the
> > existing sheet metal enclosure with separate heat sinks and multiple
> > swaged-on stand-offs is way too loose, by at least an order of
magnitude.
> >  The enclosure I have is also warped and flexes.  To me that means we
> > need a milled enclosure...
> >
> > If we're going to do that we might as well do it right and make it into
> > two separate cells with noisy digital circuits in the front and analog
in
> > the back...
> >
> > If we do that then you probably don't have to worry too much about
> > radiated emissions or changing the PCB form factor or connector...
> >
> > Filtering conducted EMI would rise to the top of the list of concerns.
> > Moving the switching frequecies of all the supplies up as high as
> > possible would ease the filtering burden on everything on the satellite
> > and tend to push any spurs out of the passband.  And so forth and so
> > on...
> >
> > Once we had some hard data on the amount and characteristics of the
> > conducted EMI from the power distribution point, then John could start
> > designing in the necessary EMI filtering and CPB layout to fit into the
> > box and meet the yet to be determined EMI susceptability requirement for
> > the receiver.  If his design didn't look like it would be able to meet
> > the requiement then there would be some push-back to the power
> > distrubution subsystem to clean up their radiated EMI, etc.
> >
> > I guess the bottom line would be that since you can't know the radiated
> > and conducted EMI susceptability of everything that may end up connected
> > to the CAN-Do module, all you can do is try to make it as clean as you
> > can and get the switching frequency as high as possible.  By the way, I
> > just looked up the Maxim converter you're using and it looks like it's
> > very lightly loaded which would explain wny its running at 5 kHz instead
> > of the 200 kHz they spec.  I spent some time looking for a better choice
> > and couldn't find anything, but I don't know what you requirements are.
> >
> > 73,
> >
> > Juan
> >
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