Assembling and grounding to metal case

Discussion in 'UDOO X86' started by Newcomer, Apr 5, 2018.

  1. Newcomer

    Newcomer New Member

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    Hello everybody! First of all congratulations for the effort and I wish you make great progress in the near future!

    I have a couple of questions regarding the x86 board, which are mostly related to the assembly, if anyone could help me, I would be grateful! I have to say that I am no expert on electronics engineering, so I am slightly clueless, those might be quite straightforward things that I ask here, but at that point in time, I am relatively confused.

    I understand about ESD safety concerns, so I assume that I have to take care while handling the board. I plan on installing an M.2 SSD and enclosing the board in the metal case, which, by the way, looks beautiful, congratulations to the designer! I am slightly unsure as to the procedure, should I drop the static-shielding bag on an antistatic grounded mat before taking it out?

    -Searching and asking around, I have seen that for optimal esd safety, it would be better if I ground the board to the case through a low resistance connection. However, I do not know how I would do that because I am not sure where on the board is a ground pin (star ground, or something like that, from what I have seen) and, of course, I wouldn't know what to use for the actual connection. So, how would I ground the board to the case and how does this help with esd safety, if I may ask?

    -Also, I have read in the instructions that plugging and unplugging USB while the device is on is to be avoided. How important is that? Should I only plug in USB, HDMI and other connections only when the board is off? Or I better have hubs connected and use those instead to plug/unplug stuff while on?

    -Is the board grounded while connected to the power supply? Will I be able to touch and move the metal case while it is powered on, with no trouble? Do I have to take additional precautions?

    -Finally, I have read in the instruction manual that "The battery is not rechargeable, and can be connected to the board using dedicated connector CN5 which is a 2-pin p1.27 mm type MOLEX p/n 53398-0271 or equivalent, with pinout shown in the table on the left". First, I think CN5 is a typographic mistake, as the connector for the battery is C1 (on the board). But my question is, is the battery not connected by default? Do I have to do something to connect it myself?

    I thank everybody for their help in advance! I must say that the x86 board is far greater up close than how it looks on the image! I look forward to powering it on for the first time!
     
  2. yankneck696

    yankneck696 New Member

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    If you are in the US, 4-40 thread. In Mertic world (The rest), you would use m3 hardware. ALWAYS use internal tooth washers, NOT external star washers !!!! They can short out close components. The best to use is SEMS screws & KEPS nuts (Already have washers built on.NO nuts on the board, due to width.
    This will all be in inches.
    Minimum .375" (3/8") Female Female (Male Female can be used, but NUTS MUST NOT BE USED ON THE BOARD, only the sheetmetal side) threaded standoff (3/16" width MAX. DO NOT use the 1/4" width). This is to clear the M.2 sockets on the bottom. Find the board artwork, be sure to scale it right. Use a center punch to position the 4 holes (Cut picture down & tightly tape it to the bottom of enclosure). Proper hole size for a 4-40 screw is .110. I always use a .125" (1/8") for a tad of play.

    Use SEMS screw, nut & internal tooth washer, OR KEPS nut, or nut, internal tooth washer (ONLY IF you can just find Male/Female spacer).
    Connect the standoffs to the base sheetmetal, rather tightly. Then, put the board on. Be sure you are lined up. BE SURE YOU ARE LINED UP !!!!! If you are & can screw 1/4" 4-40 SEMS screws gently.Snug them. You are now mounted & grounded.

    The internal toothed washers cut into the host metal & the screw head, to provide good electrical bond to the metalic structure. Same, on the circuit board.

    ABOVE ALL, DO NOT EVEN CONTEMPLATE USING THE BOARD AS A TEMPLATE !!!!!!! yOU WILL END UP THROWING IT AWAY !!!!

    You now have a well "Bonded" Udoo. Now, you need to ground it.
    In your enclosure, you have 2 options. Use the DC input & bond the negative to the case, or bring 120/240VAC, transform it to the proper voltage & connect the mains ground (Power supply MUST have the ability to bond the DC negative & AC mains ground) to the chassis WITH the 12V negative AT THE SAME POINT (Of course, with internal toothed hardware).

    In no way, am I trying to sound condescending. I am emphasizing what you NEED to know.
    I do this for a living, as the foreman of electrics of an international automation company.
    I make holes, my guys put stuff in them. Almost everything we make is "Exactly like last time, but....". It's an ever evolving job. I love it.

    I have played with my Udoo X86 Ultra with some heavy SDR (Software Defined Radio) software & it sure can get hot. I went & bought a bunch of miniature heat sinks, cut them to size, deburred, trued them up with 220 grit, then 320 grit. I then got heat transfer epoxy to adhere the heat sinks to all heat producing component that I could. he CPU will have a small fan, my SDR has one & the enclosure (100W HF-UHF ham radio SDR transceiver/VNA/spectrum analyzer/whatever I want to make it do. I built my own filtered fan forced system (As I said, I do this quite a bit).

    Any questions, ask away.

    Ed
     
  3. LDighera

    LDighera UDOOer

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    My experience has been that about 30% of the time inserting/removing a USB connector from the on-board USB connectors results in an immediate re-boot. Fortunately, today's Windows and Linux filesysystems are robust enough to recover without data loss.
     
  4. Newcomer

    Newcomer New Member

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    @yankneck696,

    I am sorry, but I really don't understand most of this. I suspect you are giving some directions on how to build a case and what to be attentive about. The truth is I already have a metal case that is ready-made. This has four small screws inside it, so that I can support the board on the metal case.

    My question was on how to ground the case to the board itself, which is something I have no idea about. Do I use a wire and connect it to between some point on the case and some pin on the UDOO x86 board? If yes, which pin is this? Also, how would this help with static electricity?

    What I also don't know is whether the board is grounded while connected to the power supply? Will I be able to touch and move the metal case while the board is powered on?

    And, finally, is the CMOS battery hanging there already connected? The manual states this as if it is not, do I have to do something with it prior to powering on?

    @LDighera,

    I guess I will have to use USB hubs then. That's ok, this is not going to be a big problem, I guess. Thank you for the info!
     
  5. yankneck696

    yankneck696 New Member

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    What I am trying to tell you, is that using internally threaded standoffs(Spacers), you move the board up .375". The metal standoffs, screws, nuts & washers will ground the UDOO to the case.

    Ed
     
  6. Newcomer

    Newcomer New Member

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    @yankneck696, so the small goldish metal region on the board that encircles the mounting holes for the screws (as seen here) is electrically connected to the ground plane of the case? In that case, if I mount it with simple screws at all 4 points, does it not pose any problem that I will have a ground connection at 4 points instead of 1?
     
  7. yankneck696

    yankneck696 New Member

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    It will pose no problem. But, you must use spacers to raise the height, to fit the NGFF units & battery.

    In my first post to you, I was a bit rushed. I will now post links on EBAY to the parts I was trying to describe.
    4-40 (#4 screw 40 threads per inch) SEMS screw
    https://www.ebay.com/itm/10x-FSC-4-...148974?hash=item3395c68aee:g:B-AAAOSwq7JUIIh-
    You will see that it has an internal tooth washer built on to make a good electrical connection, along with locking the screw in place.

    https://www.ebay.com/itm/Fascomp-20...144626?hash=item1a361ee732:g:zqgAAOSw~ZBZyQE~
    This is the 4-40 .375"(3/8 inch) female female spacer. It gives space for the parts on the bottom of the Udoo.

    Ed
     

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