Motherboard pcb modification question

There is a jumper shown in the wiki adaptions that looks like a piece of wire to connect two pins where the atx power plug used to be. what is this for? i am assuming it connects 5v through it now that the power is not coming from the atx power supply?

-aaron

Which jumper? The only one I can see in the PCB_adaptions_for_Mendel wiki page about adapting the motherboard for Mendel is the one that goes between the USB-Serial connector and the ICPS connector. This *is* so 5V will get everywhere it needs to, the wiki page itself says:

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Finally on the back of the board solder a link from the fourth pin of the 6-pin USB<->serial connector to the corner pin of the ICSP connector as shown. This allows the entire board to be powered from the USB cable.

If that is not the jumper you are referring to, please be more specific about which one we are talking about here.

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Jonathan

Hi there

I am having trouble with this one as well.

The wiki page PCB adaptions for Mendel show a jumper at A (see the modified motherboard jpg). I assume this is the jumper being discussed. Anyway, this is the jumper I am having trouble sourcing... mainly because I do not know what to look for.

What is the purpose of this jumper? Is it to simply connect the two points or does it have a higher purpose? If it is to simply join those two points then could one not simply solder a link?

Cheers

ps. here is a picture where you can see the jumper clearly to the bottom right. (image link to [www.binaryconstruct.com] thanks binary construct



Edited 1 time(s). Last edit at 06/04/2010 12:05PM by AgeingHippy.

no, there is clearly a jumper soldered across two pins where the atx plug used to be. the question is because this was not called out or explained in the wiki. it is only in the pictures and not in words.

the jumper at A is to enable auto reset. (it is labeled on the board.)

lunchtrayrider Wrote:
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> no, there is clearly a jumper soldered across two
> pins where the atx plug used to be. the question
> is because this was not called out or explained in
> the wiki. it is only in the pictures and not in
> words.

That link is mentioned in the paragraph just under the jpg of the modified motherboard on that page and says "solder in the link shown at the penultimate pair of holes on the right" ... it does not seem to say why though

>
> the jumper at A is to enable auto reset. (it is
> labeled on the board.)

I have done a bit of research and remembered some of the stuff I have done in my past. I do remember setting jumper switches for something to do with my computer or hard drive, so answering my own question - that jumper is not permanent but is used as a switch of sorts. Hence it cannot be a solder connection, but exists in two parts - a 2 pin header and a 2 pin shroud. Pretty much the same option as a DIP switch?? - There's a thought. Would it not be better to put a DIP switch there instead of a jumper? A jumper has a shroud that can get lost. comments?

I am learning all the time. I believe building a mendel is certainly going to teach me many new skills ><

lol, someone must know this, I don't want to just blindly short connections on the circuit board!

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lunchtrayrider
I don't want to just blindly short connections on the circuit board!

Then I'd suggest keeping your eyes open while soldering that link

More seriously:

(1) Why not? You are following (well, questioning!) instructions written by Zach, the person who designed that board. Either you trust his board design and layout, or you open up the design files in Eagle and check them out in detail for yourself. If you trust his board design, then it seems somewhat inconsistent to then be so suspicious of his instructions for working with his board, doesn't it?

Do you have some as-yet-unspecified reason to believe these particular instructions are incorrect? Why are you seemingly more willing to trust whatever random people (like me?) post about this, here in these forums, than what the board designer himself wrote? As Dr. Spock might say, that would be illogical.

Once I found the link you were referring to in the board image, above the green letter D:

(2) These boards are an open source design, so you are never "blind" regarding it, unless you choose to be. For example, I suggest that you could:

Run Eagle, open the schematic for this board, and check how pins 9 and 19 of that connector are labelled. Pin 9 goes to +5VSB, pin 19 (along with pins 4, 6 and 20) goes to Vcc. A Google search will very rapidly find a pinout diagram and info for a 20pin ATX connector. From that, you can confirm for yourself that pin 9 is the 5V standby supply, and pin 19 is one of the (normal) 5V supply pins. If you are feeling paranoid, you could check multiple web sources about this, and make sure they all agree. Or even obtain and read a copy of the official ATX standards documents, maybe.

Equipped with that info on what these power supply pins do, you can then reasonably either

(a) decide that's enough of a verification, by jumpering pin 9 to pin 19 you are apparently connecting two parts of the 5V power tracks on the board together, which would each be independently powered (at 5V) if you used an ATX power supply,

or, if that doesn't satisfy your need to be sure it is OK to jumper these pins, you can

(b) return to Eagle and look at the schematic again, and check where the +5VSB rail is used, and make sure that it makes good sense to you to connect the main 5V supply rail to each of those places in your Mendel setup.

(c) I suppose, if you really insist, you could then check that the motherboard traces in the PCB layout file really go from pins 9 and 19 to where the schematic indicates they should go, maybe then generate Gerber files, and verify that those do what you expect for those traces, and then check that your physical board matches the PCB layout ... but IMO this is verging on absurdity if you are not also checking out the rest of the schematic and board at this same level of detail.

I'll be interested to hear how much checking along the above lines you actually do for yourself, now (maybe everything I am posting here is just as wild as Zach's instructions to solder across those two holes -- do you have any reason to trust my words more than his?)

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Jonathan

yea consistency is probably rock solid across the wiki. because it is a wiki. that is the nature of the beast.

real issues with the the way things are wired. generally there are creative ways things are hooked up. a lot of rules of thumb are broken. for instance daisy chained ground wiring instead of star wiring.

a good explanation would be nice. to me it appears that this solely allows the board to be powered by the usb. let us say that I would rather not power this through usb and would rather hook it up to a 5v power supply. do i simply leave the link out and leave off the jumper at the usb cable connection? or leave the link in and leave off the jumper at the usb cable connection. i'm guessing that the link stays in either way and the jumper at the usb cable is either on or off depending on what I want to power the board with.

of course some of us didn't take any ee courses in college and instead have degrees in something else. why waste time learning a new program, probably screwing up using it, and still not getting an answer when the answer is easy to get from someone else?

and yea i do trust the word of people on forums on the internet. i don't think anyone here would have a reprap if they didn't.

im also a control freak and paranoid. i still screw things up and i get more paranoid. so there.