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Electronics Help-Needed: Motherboard tray docking circuit

Discussion in 'Modding' started by Captain Slug, 21 Jun 2005.

  1. Wolfe

    Wolfe What's a Dremel?

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    What kind of current can the connectors handle, and what type of connector are you using? With all those pins, the possibility of a mechanical failure grows esponentially.

    Also, you will have to worry about interference between the different calbes, and the wires that compose each cable. 80 wire ata cables use a ground between each data line to reduce coupling between each data connection. What type of shielding do you have?

    Sorry to be negative, but i wouldn't attempt something as fragile as an integrated connector. Waaaaay to many mechanical failure points.
     
  2. Ghlargh

    Ghlargh What's a Dremel?

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    You can probably get a copyright for your boards, but do not expect to get a patent for it. While this type of thing does not exist in this exact shape, there are too many similar solutions out there for you to be able to patent it.
     
  3. Xiachunyi

    Xiachunyi What's a Dremel?

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    Ah, I stand corrected.

    So from my understanding, instead of cables coming from the side and top of the motherboard, you have them connected to another board then that board just has extensions that comes from one side of the motherboard to have a "clean look". Is this what you are going for?
     
  4. Captain Slug

    Captain Slug Infinite Patience

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    1. I need people to be negative to keep me in check
    2. The sub-D connectors I'd like to use are rated for 30V 1A. Here's the mouser catalogue number page for them. If I get too close or above a 1Amp requirement the particular connection above spec will need it's own barrel plug. Something I will probably have to do with the 12V and 5V lines. I can use a couple different connectors if I need to and I'd like to consolidate the power connections away from the drive interface connections as much as possible without making disconnection/reconnection difficult.
    3. The IDE extensions will obviously need to be sheilded with wire mesh or just isolated from other wires within the plug-bus enclosure.
    Pretty much. It's just consolidating every connection on the motherboard into a single area to allow quick disconnection/reconnection. This was originally meant to be integrated into the motherboard tray itself but I decided that I wanted the plug-bus to be optional.
     
    Last edited: 23 Jun 2005
  5. ZapWizard

    ZapWizard Enter the Mod Matrix

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    I think you are well on your way to getting this designed.

    The only thing I can add is to look for multi-pin connections on Mouser (You linked) and Digi-key. The motherboards they use in development labs often have add-on boards with all the connections to keep things modular and easy to work on. I have seen everything from PCI-slots to complex connectors with hundreds of pins used to connect the motherboard and daughterboard.
     
  6. fatal_error

    fatal_error What's a Dremel?

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    Nice idea but your going to have to think harder about the sata connectors. Resistance is important, not so much that the cable needs to be a specific resistance, but more that from the motherboard to the drive the cable must have a constant impedance otherwise signal reflections are going to start causing problems (think similar to what happens to light when it goes into water). Also there's going to be massive ammounts of crosstalk with 6 connectors running on the same circuit card unshielded. I'd look a lot more into this before you make it. Good luck though it could turn out to be a really nice product.
     
  7. splashdream

    splashdream What's a Dremel?

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    ok, here is a thought for you...what about using a single edge board connector for the interconnect between the two pcbs? this will make the PCB design a little more complex but afford you a lot more flexibility in design as board edge connectors are very close in design to agp, pci-e, pci, and isa slots and afford you plenty enough pins and support for the power you will be passing between the two boards without having to have numerous connectors specifically for power. in addition, it will give you an easier to "lock" connection between the MB tray and the case pc component pcb.

    just a thought...

    also, as to the crosstalk issues given the short spance the circuit will travel there will be no adverse affect due to the lack of shielding of the interconnects such as the IDE and SATA connections....if this is a concern at all just segregate the power and data connections into clearly seperated "zones" so that they don't overlap or run parallel to one another. something else to remember when designing the PCB is to make no right angle traces as you will have digital signal and power running on the same pcb's.
     
  8. Captain Slug

    Captain Slug Infinite Patience

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    I would LOVE to have this made into a PCB if at all possible.

    The design of the two halves is still completely undecided and I need considerable professional help in its design and construction.
    This is going to take alot of work but potential of the end result is what's driving me forward.

    Admittedly I'm almost a complete dunce when it comes to electronics. Which is why I need someone who knows what they're doing to finish the design work on this thing.

    Edit: Through another AIM conversation I've solved the SATA interfacing problem. Instead of adding 3 points of resistance by putting SATA terminals on each side of the plug-bus I've come up with a much simpler solution. Just basically cut a SATA cable in half and add connectors. Then add screw-mounting points to the plug-bus allowing you to secure the connectors to the halves of the plug-bus so that when the halves are joined the cable halves are connected.

    This not only reduces the resistance to a minimum, but it also make manufacture simpler since it removes a large number of pins from the connector requirement. A similar solution could be implemented for the IDE cables if desired.
     
    Last edited: 25 Jun 2005
  9. sui_winbolo

    sui_winbolo Giraffe_City

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    Yeah, I've seen something very similar to this in a Gateway HTPC (those small ones couple years back)
     
  10. Ghlargh

    Ghlargh What's a Dremel?

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    This solution is fairly normal for the PCI/ISA ports on some OEM machines, f.ex. HP Vectra. The motherboard is fairly easily removable, but the expansion cards stay in the case.

    And as i said, i saw allmost exactly this construction in an old MAC, only difference was that, being OEM, it had the motherboard side of this connector allready integrated into the motherboard meaning you could rip the board out without removing a single wire.
     
  11. fatal_error

    fatal_error What's a Dremel?

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    That seems like a reasonable solution, nice one.
     
  12. matrixops

    matrixops What's a Dremel?

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    I sent you a pm regarding this Captain Slug
     
  13. Captain Slug

    Captain Slug Infinite Patience

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    Thanks to a heap of feedback, criticism, cooperation, and head-scratching the design for the plug-bus has actually become quite simple.
    [​IMG]
    The upper section contains all of the power connectors and except for a few power traces to feed the light power output and fan controller it's an independent unit and can have it's own type of interconnect capable of handling the required current load. Whatever interconnect is used the pin requirement is only around 50 for this layout.

    The middle section will just be a series of precisely positioned threaded mounting holes for attaching the flush-mount cable extensions (on the motherboard side) and the flush-mount rounded IDE and SATA cables (on the case side). This section will require custom cables, but no actual circuitry.

    The lower section serves 3 functions.
    1. Front-Panel extensions (Power/Reset, LEDs, USB2.0, Front Audio, 9-pin Serial header)
    2. Light control (2 switches that toggle the 4-pin connectors)
    3. Fan controller (on the Front-Panel PCB itself)

    The front panel PCB will contain all the switches, ports, and fan controlling electronics. It can connect to the Plug-Bus with one or two cables. It's size limit is 8x2 inches.
    The serial header extension is meant as a pass-through for an LCD unit. This could either be a header on the plug-bus, or an actual DB9 connector.

    I have a small handful of people helping me move along with the design of this and although I don't know when it will be made I feel extremely confident that this rendition will work as it should without being too expensive or difficult to make.
     
  14. crappish

    crappish What's a Dremel?

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    I say it once more. You can forget patenting this. Well, can't really speak for the US, since people seem to be able to patent the weirdest things in there (like internet) but at least I can say that show won't work in EU. At least in here, one of the rules in patent pending says that the subject of patent must not been previously presented, in public, in any ways. And I believe Bit-tech forums is rather public...
     
  15. Captain Slug

    Captain Slug Infinite Patience

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    Okay whatever. I just want to see it made at a level of quality that people will be happy with. I don't want to milk it like a prized cash cow or anything.
     
  16. Captain Slug

    Captain Slug Infinite Patience

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    Bump!
    I am now willing and able to have this made in PCB form if anyone has the capability to do so for me.
     
  17. Captain Slug

    Captain Slug Infinite Patience

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    After getting some good advice from my friend's father who used to built alot of custom sensor circuits I've started designing the PCB through software. Here's what I have so far, the board dimensions are 1.25" x 12" and will be made from two-sided extra thickness copper boards.

    http://www.captainslug.com/modding/mk6_plug-bus_th_pcb.gif
     
  18. Captain Slug

    Captain Slug Infinite Patience

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    Some of the traces on that design are too small and I decided to go with different connecctors in order to simplify the PCB.
     
  19. Splynncryth

    Splynncryth 0x665E3FF6,0x46CC,...

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    You may have some issues with the board design. Because of the high frequencies, there does need to be some consideration, but you may be able to get away with it. Many of the standards in the PC have some 'slop' in them to account for those who will implement the standard poorly. The biggest trick will be the connectors. For the high speed stuff, look to see what speed the connector is rated for.
    As for the RF PCB design, there are some packages out there, but I don't know any that are free, and the ones I do know, I only have a passing familiarity with them. Any PCB design I did was by hand.
    I think what people have been trying to say about things such as SATA is that the transmission line must have a 100 ohm impedance at the operating frequency (Z=100). But, I think if the traces are short, you may be able to get away with it. Make sure you shield adjacent interfaces with a proper ground plane.
    As for the power connector, you need to make sure there is enough trace on the PCB to handle the current. Take the AMD 64 CPUs (the single core). Looking at the thermal and power data sheet, the max current draw is a little below 58A. That is a lot of current (and one reason the CPU has so many pins). The other design consideration is to keep the power away from the data lines. The changes in current draw will cause EM spikes that can interfere with your data lines.
    The only other help I can offer is to look for some design examples, these may have some canned examples you can use in your design.
    BTW, I love the idea, it sounds really ambitious.
    Best of luck.
     
  20. Captain Slug

    Captain Slug Infinite Patience

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    Okay, I've basically started the PCB design over from scratch because of my previous inability to take into consideration the peak current load requirements of certain traces. In deciding upon different connectors and consolidating some portions of the PCB for better trace connections I've managed to turn this into a fairly simple single-sided design that I can make with a higher weight copper-clad board.

    Here's the new schematic: http://www.captainslug.com/modding/mk6_plug-bus_th_pcb2.gif

    The other board is going to need to be double-sided but shouldn't prove too complicated.

    Yeah, I found a simple solution for this last month in the form of an existing product.
    [​IMG]
    4 of these will simply be install on an array bolted on-top of the Plug-Bus so that they connect in-sync with everything else. The end result is that the Plug-Bus PCB facilitates nothing more than power connections.
     
    Last edited: 21 Dec 2005

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