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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/726WV5SXYDERVQ7CT2FK4SOBSQTKP2FU/?format=api", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api", "message_id": "000901c7c249$703410d0$0301a8c0@Shop", "message_id_hash": "726WV5SXYDERVQ7CT2FK4SOBSQTKP2FU", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/RQX4DLDIYY3MVVVNFRFO357N5UXLTUIQ/?format=api", "sender": { "address": "juan-rivera (a) sbcglobal.net", "mailman_id": null, "emails": null }, "sender_name": "Juan Rivera", "subject": "[eagle] Re: CAN-Do-Too! ??????????", "date": "2007-07-09T16:51:45Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/67GB3DVX35OY2RFF2TT6GQAONRPIJWWI/?format=api", "children": [ "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/3PDTDMVBL2KNT6TWQ2MVK3SD65K3EDJL/?format=api", "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/L5WG7XJ4AQDHAXKMMCB5ZTYASJ4XSKRD/?format=api" ], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "Chuck and Lyle,\n\nI'm in the process of writing up my presentation for the next AMSAT\nsymposium so all of these issues have been on my mind constantly as I write.\n\n\nI believe that any modification of the CAN-Do module should flow out of a\ncomprehensive review of the top-level satellite requirements. There needs\nto be an EMI specification that covers radiated and conducted emissions and\nsusceptibility for Eagle. Any need for changes to the CAN-Do module should\nflow directly from that EMI spec. An analysis of the requirements might\nshow a need to break the module enclosure into two sections. If the module\nenclosure was changed to a two-section configuration, with all of the\ndigital electronics in the front and the analog in the rear, then the RF\nwould need to enter and exit out the side. If that were the case, I believe\nthat the existing CAN-Do PCB size would be OK as currently configured. And\nof course, all of the above would directly impact the next revision of the\nreceiver since it would determine the physical layout of the PCB as well as\nthe size and configuration of any EMI filtering that was needed.\n\nAn analysis of the Eagle EMI requirements might also show that a move to a\nmuch higher switching frequency would be advised since it would ease the\nburden on filters and move any artifacts outside the passband of most analog\npayloads.\n\nBottom line - I would hold off making any hard decisions until a\ncomprehensive EMI requirement for Eagle is created and analyzed.\n\n73, Juan\n\n\n\nIf designing a new power supply is determined to be necessary then I would\nstrongly suggest a move to as high a switching frequency as is practical.\nThis will make filtering much easier.\n\n-----Original Message-----\nFrom: Chuck Green [mailto:[email protected]] \nSent: Monday, July 09, 2007 7:57 AM\nTo: [email protected]\nCc: [email protected]; Bill Ress; Dave Black (Home); Dave Black (Work); Dave\nhartzell; David Smith; Don Ferguson; Juan.Rivera (Work); Samsonoff@Mac. Com\nSubject: CAN-Do-Too! ??????????\n\nHi Guys,\n\nJuan has done a lot of outstanding work which resulted in some \nsubstantial critiquing of the CAN-Do! (Affectionately called a \n\"widget.\") It is unfortunate that it has taken several years since the \nCAN-Do! was designed and then 100 units built before an application of \nsufficient sensitivity used it to discover it's shortcomings. History \ncan provide lessons that I hope we can learn from, but it seldom \nprovides solutions to the problems encountered. Lyle and I have \nexchanged a few thoughts privately and it seems it may now be time to \nconsider solutions to the problems found.\n\nThe only practical way to accomplish this is to develop the next \ngeneration CAN interface device. Dare I call it the CAN-Do-Too! ?\n\nAll technical specifications should remain the same. What this really \nmeans is that a next-generation controller must run *exactly* the same \nfirmware currently running the CAN-Do! .\n\nAll specifications added or redefined should be carefully defined and be \nmeasurable.\n\nGeneral specifications that we worked from before were that the widget \nshould use as little power as possible and consume as little of a \nmodule's volume as possible. The first of these should remain the same, \n\"use as little power as possible.\"\n\nBut the second should be changed to \"consume as little of the connector \npanel space as possible\" even if it means consuming a little more of the \nmodule volume. This means the widget PCB and components should not \nextend beyond the dimensions of the DA-15P connector in either \ndimension. A possible compromise to this would be to let the PCB run \npast one end of the DA-15P but not more than the DA-15P is forced away \nfrom the side of the box by the box design.\n\nThe power supply could be completely redesigned. Or the inductor of the \nexisting supply could be exchanged for one that is a toroid (the \nexisting one is not). If someone wants to step up and design a new \npower supply, great! If not, then we would simply change the inductor. \nI'd sure like to see someone take this on. With so many of these in the \nsatellite, only a few milliwatts is important. And the noise issue Juan \nuncovered is *very* important.\n\nIt may be that some, or maybe all, of the widget should be enclosed in a \nmetal box. It may be that just changing the inductor would allow a new \nwidget to meet the yet-to-be-defined noise specifications.\n\nThe input power filter for module power should be separate from the \nwidget power supply input filter. The module power filter is a filter \nthat will not meet all module requirements, but would likely meet the \nrequirements of a digital module. Some modules, such as receivers, may \nneed additional power conditioning. But in any case, the widget power \nsupply should not add to the module power supply noise.\n\nThere should be a simple way to disconnect the filter capacitors on the \nwidget from the data lines when the widget is in Byte mode. Most people \nare not aware of this problem which was uncovered by another module \nbuilder. It only effects those using the CAN-Do! in Byte mode.\n\nUsing a synchronizing signal does not seem practical to us. It would \ncomplicate the design of the widget power supply so that it would \nfunction with or without the presence of the synchronizing signal (we \ndon't want to introduce a single-point-of-failure). It would \ndramatically increase the satellite wiring harness complexity, something \nthe widget was intended to a simplify. And it would inhibit the widget \npower supply from going into various power-saving modes.\n\nRecruit some new people into this project. Lyle simply doesn't have any \ntime for doing new designs right now. We need a power supply designer \nas stated above. And my time is limited. I'm willing to lay out the \nnew design and build a few prototypes, but I need others to do parts \nprocurement and volume building of widgets. I'll prepare flight units \nif desired. We've talked about having someone skilled in parts \nprocurement before but I don't know of anything having come of it. The \nbottom line, if this is going to happen, Lyle and I need others to be \ninvolved.\n\nIf you think this is a good idea, or bad, please express yourself. And \nif you have other comments to add to the above, or would like to \nmodify/expand on above comments, please do so.\n\nLooking forward to your comments,\n\nChuck and Lyle\n\n\n", "attachments": [] }