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Thread: power supply questions. + Schematic

  1. #1
    Maximum Bitrate Raas's Avatar
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    Post power supply questions. + Schematic

    Hi All,

    I have some questions about powering the computer.

    At home, I have 2 ATX desktops. They both have the option in the Motherboard's BIOS to power on when power applied.
    Now, the carputer I'm building doesn't have this option in the BIOS, so I must push the power button to Power up this computer.

    Now I'm not really sure how this works.
    Does the motherboard TELL the power supply to turn on when I press the button or what ??

    I ask this because I might design my own schematic from sample designs taken from the datasheets of the components. Because,

    When I (well, actually a friend who has far better experience with these tings) have made a psu, with a power-good signal, and I turn on the psu (so that it gives all the good voltages, and a bit later the power-good signal) the computer would start wouldn't it ?
    (I guess so, because the motherboard gets powered, it's only a different trigger that tells the psu to turn on, Right ????)

    I just got back from holiday, and took some datasheets and paper with me. (My girlfriend had to study for an hour each day, so I though I could do some reading and drawing.)
    So I came up with THIS SCHEMATIC. I'm sorry I draw it on paper, but I didn't have a laptop where I could draw it on.

    It only doesn't have a Power-Good-Signal, but I'm going to use something like sproggy used, And I doesn't have a relay to turn it on, but it's only a start.

    What do you think ????
    (Comments please, maybe I could improve something, and there could be some things I guess)

    Greetz

    PS... I hope you can read the schematic, I draw it on plain paper, scanned the image in a 600dpi resolution, and then put it in Acrobat.

    [ 10-23-2001: Message edited by: Raas ]
    Raas - The Netherlands
    ME: VIA epia m10000, lilliput 7', opus 150w, 80gb<br>
    GF: IBM Thinkpad 380, ext. 3.5 80gb, 40x4, PB-IR

  2. #2
    FLAC
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    You can't just tie the outputs of DC-DC switcher circuits together. What happens if one is set to regulate to 5 volts and the other one is set to regulate to 5.01 volts? One turns on, the other turns off. Who let the smoke out?
    You either need diodes or inductors.
    MPEGBOX - Plexiglass Computer
    www.mpegbox.com

  3. #3
    Maximum Bitrate Raas's Avatar
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    Thanks Jeff,
    This is the kind of info I would like to get.

    Whoops..
    I got that (output joining) from sproggy, BUT I OVERLOOKED SOME THINGS.

    In schematic from sproggy it says you can join the output's but I missed 4 parts. or maybe some diodes

    But what do you think of it ?
    Could this be a good power supply ?

    And what about the other questions I asked ?
    Anyone (what the exact procedure is to power a pc, and what happens during this period)

    Thanks in advance !

    Greetz
    Raas - The Netherlands
    ME: VIA epia m10000, lilliput 7', opus 150w, 80gb<br>
    GF: IBM Thinkpad 380, ext. 3.5 80gb, 40x4, PB-IR

  4. #4
    FLAC Mastero's Avatar
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    Cool

    my dear friend ... your drawing is so confusing ... im sorry .. but it is ...

    Anyway you want to start the ATX board with the DC-DC supply using the soft start?

    When i say soft start meaning there is a button on the Mobo which stats the PSu right !
    now wat happens is the ATX PSU has a contant 5vdc to the MOBO which is called the standby 5v when u press the button the stby 5V is sent back to the PSu which enables the PSu using a relay. and the PSU goes on full power got it so when u have a PSU like the sproggys design which has all the volts execpt the 5V stby the mobo starts when it receives the power good signal. and does not depend on the Stnd by current....

    further if you use the sproggy designed ATX the board will not boot with the soft switch but when the power is applied to the PSu

    phew im tired .... :-)

    I have searched the entire web and found the sproggy designed to be the best for in car entertainment... so i have made few extra just ... check out the sale section of this forum

    Mastero

  5. #5
    Maximum Bitrate Raas's Avatar
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    my dear friend ... your drawing is so confusing ... im sorry .. but it is ...
    Yes, you are absolutely right about this, but once again, I was on holiday, I only had pen and paper and some data-sheets, and I had nothing to do 'cause my girlfriend was study-ing (?!?).
    I started somewhere, and while I was busy it grew and grew. I have to mention that this is the first time I drew something like this.
    When I got back from holiday I had this schematic just lying around, And I thought I would share it with you all.
    BTW. did you print it on a laser-printer ??
    because when I print it, it is readable.
    If you can't read it, you could also use the datasheets of the components used. I used sample schematics from them.

    .....and the PSU goes on full power got it so when u have a PSU like the sproggys design which has all the volts execpt the 5V stby the mobo starts when it receives the power good signal. and does not depend on the Stnd by current....
    Thank you for this info.
    So, when I put power through the power-supply, (all the voltages get regulated, and delivered to the mb) and the power-good-signal is send to the mb, The computer starts to boot.

    I have searched the entire web and found the sproggy designed to be the best for in car entertainment... so i have made few extra just ... check out the sale section of this forum
    I already have all the regulators for this supply and some more. (4x max1771, 4x max787, 2x max788, 2x max774 and 2x max775)
    I'm absolutely sure this friend of mine can assemble and solder it. (It's his work, but, just like me, he doesn't have any design-experience, so) I just need a good schematic to build.

    -----------------------
    In Addition to Jeff Mucha's Post
    Q. Which components do I need to tie the voltages to eachother ? I mean, Is there some kind of component I can use at every voltage ? (3,3 5 12)
    -----------------------

    A lot off questions for ya all, but I really hope ya all can help me..
    hehehe.. something like an open-source-power-supply

    That's it for now !
    Greetz,
    Raas - The Netherlands
    ME: VIA epia m10000, lilliput 7', opus 150w, 80gb<br>
    GF: IBM Thinkpad 380, ext. 3.5 80gb, 40x4, PB-IR

  6. #6
    Maximum Bitrate Raas's Avatar
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    No one ?

    Well, I guess it's all up to me then.

    I'm going to try this with this friend of mine.. it'll work with some adjustments.

    Greetz
    Raas - The Netherlands
    ME: VIA epia m10000, lilliput 7', opus 150w, 80gb<br>
    GF: IBM Thinkpad 380, ext. 3.5 80gb, 40x4, PB-IR

  7. #7
    FLAC
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    Originally posted by Raas:
    <STRONG>No one ?

    Well, I guess it's all up to me then.

    I'm going to try this with this friend of mine.. it'll work with some adjustments.

    Greetz</STRONG>
    Sproggy used 10 uh inductors to isolate the parts. You could do the same thing.
    MPEGBOX - Plexiglass Computer
    www.mpegbox.com

  8. #8
    Maximum Bitrate
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    I think this power supply might be a bit of overkill, no? Unless you plan on powering a tank! =)

    There are many people running computers off of the sproggy power supply fine, and I think to get a bit more juice you only need 1 or MAYBE 2 extra power circuits, but I think you've gone a bit overboard.

    But please let us know how it all worked out!!
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

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