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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/NDIT4MYDS6GY37WMTFKFL5AO4CC27UYX/?format=api", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api", "message_id": "[email protected]", "message_id_hash": "NDIT4MYDS6GY37WMTFKFL5AO4CC27UYX", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/RQX4DLDIYY3MVVVNFRFO357N5UXLTUIQ/?format=api", "sender": { "address": "ku4os (a) cfl.rr.com", "mailman_id": null, "emails": null }, "sender_name": "Lee McLamb", "subject": "[eagle] Re: CAN-Do Suggestions from Juan", "date": "2007-07-19T01:56:44Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/B26QXLNBB6EMG3DNDPVKK4UYMIA3NUBC/?format=api", "children": [ "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/V5LIXR36GF23L4IDMLGOMF2O2HK556PL/?format=api" ], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "As we consider flex stresses we also need to ensure we've considered the \nlaunch adapter specs for G-forces and are providing adequate support for the \nboards.\n\nFor ESPA: 10.6 G on all axis \nFor ASAP5:\nX +/- 6 g\nY +/- 6 g\nZ -7.5 g / +5.5 g\n\nLee-KU4OS\n\nOn Wednesday 18 July 2007 08:41:23 Robert Davis wrote:\n> Jim, Juan, and all,\n> I'm sorry for not being active in this conversation earlier. I'm absolutely\n> creamed at work. I forecast being at my maximum at work for about another\n> week or two. I'll spare you the details.\n> I am sure that we can redesign a module that is at least partially milled,\n> that will maintain the flatness that Juan quotes from a vendor of .008\" per\n> 1\". It really isn't that hard, but absolutely throws out the sheetmetal\n> baseplate we've had until now. In my mind, for this one issue it's only a\n> decision as to whether the entire module height is milled (and then there's\n> just a simple flat cover) or whether the milled portion is part of the\n> height of a module and a shorter \"bent cover\" is used. I think I'm favoring\n> a milled module with simple flat cover.\n> For the issue of the isolation of the CAN-DO in a separate compartment,\n> this can be done and I guess I've seen it frequently with milled modules.\n> I'd like to avoid it because it moves farther towards having truly\n> customized modules, instead of a generic with minor connector or heatsink\n> mods. For the issue of the RF connectors exiting the side of the module,\n> this is potentially a larger issue. In our current arrangement, we have\n> identified a connector face on the modules because all the modules are\n> (potentially) packed side-by-side to consume a dimension of the spacecraft.\n> If we had an accurate accounting of how many modules, and what sizes they\n> are, then we might be able to say with confidence what gap is present\n> between modules available for RF connections. I've attached a spreadsheet\n> with the only accounting of modules that we've attempted and it's pretty\n> old.\n> The flip side of this would be: impose a requirement on mechanical to\n> provide room for RF connectors on specific (or all) modules, and specify\n> what the module sizes are and we can see where we stand. Maybe it would\n> help to have an idea of what kind of protrusion from the side of a module\n> we're talking about. 20mm?\n> So, comments on the list of modules & sizes can get us started with\n> determining what is available next to a module for RF.\n> bob\n> Robert Davis\n> KF4KSS\n>\n> On 7/17/07, Jim Sanford <[email protected]> wrote:\n> > Team:\n> > Some comments on this thread, as I indicated earlier.\n> >\n> > In no particular order:\n> >\n> > \" . . working in a vacuum.\" To not do so is why we have EaglePedia, and\n> > why I have been pushing for requirements and sharing of lessons learned.\n> > The harsh reality is that Juan and his team have been testing some of our\n> > stuff in new ways, and we're learning things. Perhaps we could/should\n> > have learned some of these things in the past, I don't know. We didn't,\n> > but we know them now, so let's press ahead.\n> >\n> > Regarding the board flexing issue: Juan, please add this to your lessons\n> > learned. It would be a welcome addition to the component selection talk\n> > that Lyle gave at Pittsburgh. In the mean time, please extract all the\n> > things that you've learned we should do differently into a text document\n> > that I can add to the lessons learned sub page from my project management\n> > page. I'll get Dave to post, this is all good stuff.\n> >\n> > Milled enclosure: Bob Davis is looking into that. I've asked Dick\n> > Jansson to locate an unmodified sheet metal enclosure to get into Juan's\n> > hands for evaluation. Many considerations here, let's make decisions\n> > based on EVALUATION.\n> >\n> > EMI: We need requirements, but nobody has stepped up to write or\n> > extract. My threat (grin) to dig out the MIL-SPEC was properly\n> > incinerated. So, we still have no requirements. I offer the following\n> > \"top level\" EMI requirements, based on my earlier post regarding the 3\n> > things it takes to have EMI:\n> > 1. Every potential EMI source (like switching power supplies) should\n> > be as quiet and well shielded as reasonably posible.\n> > 2. Every potential EMI victim should be as immune to conducted and\n> > radiated (other than on-channel thru the antenna) as reasonably possible\n> > I'll leave it to guys like Tom Clark to tell me what exponent we should\n> > attach to the value of this in the aggregate of many sources and victims,\n> > I just know that attention to the basics on a per module basis will make\n> > our lives much easier at integration/testing time.\n> >\n> > We also need to standardize on IF output levels from RX modules and input\n> > levels from SDX to TX modules. Volunteers?\n> >\n> > I think the above provides all the guidance we need to proceed with an\n> > electrical redesign of the U RX based on what we've learned so far. \n> > We'll need Bob's input on housing studies and we'll need to assess what\n> > the CAN-Do! team is up to before committing to PCboard layout and\n> > construction. Juan thinks we should wait until some top-level specs are\n> > better refined; we'll come through this discussion.\n> >\n> > Regarding the CAN-Do widgets: The team has offered to do a redesign. \n> > I'm reluctant to get too carried away on this. We've learned some things\n> > that we'd like to change regarding the power supply, but the rest of it\n> > works, and we should not toss that. So, this is an area where I very\n> > strongly feel that incremental improvement is in order, not a wholesale\n> > redesign. My sense is that the power supply noise issues we've\n> > discovered IN TESTING were not anticipated by design folks who are not\n> > necessarily power supply experts. (Bdale just confirmed this on the\n> > phone.) Now that we have them, we're seeking such experts. We may get\n> > some input soon from someone who is such an expert who knows somebody who\n> > knows somebody who is on the team. If any of the rest of you have such\n> > expertise or know somebody who has it, please step up to the plate. I'm\n> > gratified at the willingness of the CAN-Do! team to do whatever it takes,\n> > but DO NOT want to toss the baby with the bath water -- we then start\n> > over, and cannot afford that in time, intellectual effort, or $$ Part of\n> > this discussion is the recent conversation regarding high density\n> > connectors. If we need them and they're acceptable, so be it. Some seem\n> > to think this is a big deal, I do not -- it's a technical issue to be\n> > evaluated and dealt with.\n> >\n> > One commentor expressed disappointment about silence regarding these\n> > changes and lack of direction from \"management\". I have been following\n> > this conversation closely, but have not weighed in since I had no new\n> > thoughts or extraordinary value to add. Rest assured, I follow these\n> > issues closely, and try not to weigh in unless I have something\n> > significant to say. My silence to this point should be interpreted as\n> > satisfaction with the conversation and apparent direction. If ever you\n> > think I should weigh in and am not, ask the explicit question.\n> >\n> > Chuck asked if someone would pursue alternative inductor components to\n> > reduce radiated noise. I have asked Juan to see of Project Oscar would\n> > take this on. I think there is tremendous value in testing with\n> > substitues of this single component.\n> >\n> > Finally: SYMPOSIUM\n> > It is CRITICALLY important that we demonstrate something this year. We\n> > need it to dispel doubts and we need it to encourage fund-raising. Our\n> > hosts, the Wireless Association fo the South Hills (WASH) have committed\n> > to helping us do this. They will provide a 30+ foot tower on a trailer,\n> > antennas, coax, and I'll provide a power supply. We have a working\n> > U-band RX, and may have a better one. Bob McGwier assures me that we'll\n> > have a working SDX to demonstrate. I'll get a 2m TX for it to drive at\n> > significant power. This will allow us to demonstrate Eagle in the hotel\n> > and in the surrounding area -- vital for publicity and fundraising. We\n> > also need to show IHU and CAN-Do!, ifthey're working and sending\n> > telemetry on the \"downlink\", so much the better!\n> >\n> > We have much to do in a few short months. Let's get on with it.\n> >\n> > Thanks & 73,\n> > Jim\n> > [email protected]\n> >\n> >\n> >\n> >\n> >\n> > Juan Rivera wrote:\n> >\n> > Chuck,\n> >\n> > Forgive this long email...\n> >\n> > SInce everything is interrelated the only way to deal with it is from a\n> > system engineering perspective (in my opinion). You can't design the\n> > various subsystems with each group working in a vacuum. If you do, this\n> > is what happens.\n> >\n> > For example: I've researched the maximum amount of bending that should\n> > be allowed on a SMT circuit board. AVX, the capacitor manufacturer,\n> > suggests a maximum bend radius spec for SMT circuit boards of 60 inches. \n> > That works out to 0.0084\" maximum deflection over any 1\" segment. That's\n> > about the thickness of three sheets of paper. The tolerances of the\n> > existing sheet metal enclosure with separate heat sinks and multiple\n> > swaged-on stand-offs is way too loose, by at least an order of magnitude.\n> > The enclosure I have is also warped and flexes. To me that means we\n> > need a milled enclosure...\n> >\n> > If we're going to do that we might as well do it right and make it into\n> > two separate cells with noisy digital circuits in the front and analog in\n> > the back...\n> >\n> > If we do that then you probably don't have to worry too much about\n> > radiated emissions or changing the PCB form factor or connector...\n> >\n> > Filtering conducted EMI would rise to the top of the list of concerns.\n> > Moving the switching frequecies of all the supplies up as high as\n> > possible would ease the filtering burden on everything on the satellite\n> > and tend to push any spurs out of the passband. And so forth and so\n> > on...\n> >\n> > Once we had some hard data on the amount and characteristics of the\n> > conducted EMI from the power distribution point, then John could start\n> > designing in the necessary EMI filtering and CPB layout to fit into the\n> > box and meet the yet to be determined EMI susceptability requirement for\n> > the receiver. If his design didn't look like it would be able to meet\n> > the requiement then there would be some push-back to the power\n> > distrubution subsystem to clean up their radiated EMI, etc.\n> >\n> > I guess the bottom line would be that since you can't know the radiated\n> > and conducted EMI susceptability of everything that may end up connected\n> > to the CAN-Do module, all you can do is try to make it as clean as you\n> > can and get the switching frequency as high as possible. By the way, I\n> > just looked up the Maxim converter you're using and it looks like it's\n> > very lightly loaded which would explain wny its running at 5 kHz instead\n> > of the 200 kHz they spec. I spent some time looking for a better choice\n> > and couldn't find anything, but I don't know what you requirements are.\n> >\n> > 73,\n> >\n> > Juan\n> >\n", "attachments": [] }