Laptop power brick to power a non-laptop mobd?

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Does anyone have the experience of modifying a typical laptop power brick so
that it may be used to power a non-laptop ATX motherboard?

I have a home-made "set-top" box which usually has the following components
connected and nothing else:

one microATX motherboard with on-board video and on-board sound
one 600 MHz Celeron CPU,
64 MB PC133 RAM,
one 4GB laptop hard drive (adapted for use in a non-laptop environment),
one character LCD display (connected via a serial port),
one external USB keypad

Right now, I have modded a regular ATX power supply (replacing the bulky
metal case with acrylic covers for protection), put the insides of the PS in
my box, and mounted the PS back-panel at the back of my box. Everything
works great.

My "dream" is to get rid of all this ATX PS stuff and see if I can take a
"laptop" approach to powering. To be more specific, say I have a Dell laptop
power brick with the following specs:

AC input: 50-60Hz, 100-240V, 70-90VA
DC output: 18.5V, 3.8A

Would it be insanely messy to derive all the power lines needed for the ATX
power plug on the motherboard from the laptop power brick? All suggestions
will be greatly appreciated.
Al-U
4 answers Last reply
More about laptop power brick power laptop mobd
  1. Archived from groups: alt.comp.hardware.homebuilt (More info?)

    On Thu, 15 Jul 2004 20:25:53 GMT, "alpha_uma"
    <none_such@home.com> wrote:

    >Does anyone have the experience of modifying a typical laptop power brick so
    >that it may be used to power a non-laptop ATX motherboard?


    yes
    Essentially, the laptop power brick is (almost always) a single
    higher voltage, it has no relation at all to an ATX power supply.
    The laptop has an internal power supply that simply converts from
    higher voltage DC to lower DC, instead of higher AC to DC as with
    an ATX.

    In other words, there is absolutely zero benefit to using a
    laptop power supply, except in a very unusual situation, like
    middle-of-desert-no-other-parts-around.

    >I have a home-made "set-top" box which usually has the following components
    >connected and nothing else:
    >
    >one microATX motherboard with on-board video and on-board sound
    >one 600 MHz Celeron CPU,
    >64 MB PC133 RAM,
    >one 4GB laptop hard drive (adapted for use in a non-laptop environment),
    >one character LCD display (connected via a serial port),
    >one external USB keypad

    So far so good.

    >Right now, I have modded a regular ATX power supply (replacing the bulky
    >metal case with acrylic covers for protection), put the insides of the PS in
    >my box, and mounted the PS back-panel at the back of my box. Everything
    >works great.

    .... but it needs AC 110-230 input and you want low voltage DC
    input, right?


    >
    >My "dream" is to get rid of all this ATX PS stuff and see if I can take a
    >"laptop" approach to powering. To be more specific, say I have a Dell laptop
    >power brick with the following specs:
    >
    >AC input: 50-60Hz, 100-240V, 70-90VA
    >DC output: 18.5V, 3.8A
    >
    >Would it be insanely messy to derive all the power lines needed for the ATX
    >power plug on the motherboard from the laptop power brick? All suggestions
    >will be greatly appreciated.


    Yes, it would be messy... far easier, smaller, and maybe even
    cheaper to just buy a ready-made solution.

    What you'd want is an LDO regulator for the 12V, and a step-down
    switcher for 5V, 3V derived from that. You don't need -5V, -12V,
    or 5VSB. These are sometimes integrated into single power boards
    for use with Via miniATX et al.

    http://www.mini-itx.com/store/default.asp?c=10
    http://www.logicsupply.com/product_info.php/products_id/204

    A Google search will find more sources, those were only examples.
  2. Archived from groups: alt.comp.hardware.homebuilt (More info?)

    In article <lLBJc.34358$od7.22289@pd7tw3no>, alpha_uma says...
    > Does anyone have the experience of modifying a typical laptop power brick so
    > that it may be used to power a non-laptop ATX motherboard?
    >
    > I have a home-made "set-top" box which usually has the following components
    > connected and nothing else:
    >
    > one microATX motherboard with on-board video and on-board sound
    > one 600 MHz Celeron CPU,
    > 64 MB PC133 RAM,
    > one 4GB laptop hard drive (adapted for use in a non-laptop environment),
    > one character LCD display (connected via a serial port),
    > one external USB keypad
    >
    > Right now, I have modded a regular ATX power supply (replacing the bulky
    > metal case with acrylic covers for protection), put the insides of the PS in
    > my box, and mounted the PS back-panel at the back of my box. Everything
    > works great.
    >
    > My "dream" is to get rid of all this ATX PS stuff and see if I can take a
    > "laptop" approach to powering. To be more specific, say I have a Dell laptop
    > power brick with the following specs:
    >
    > AC input: 50-60Hz, 100-240V, 70-90VA
    > DC output: 18.5V, 3.8A
    >
    > Would it be insanely messy to derive all the power lines needed for the ATX
    > power plug on the motherboard from the laptop power brick? All suggestions
    > will be greatly appreciated.
    > Al-U
    >
    You can't do it. Quite simply the block can't provide enough power. Yes
    it powers a laptop but laptops use far more low powered components than
    a desktop. A laptop PSU also only outputs one voltage. A PC PSU outputs
    -12V, -5V, 0V, 3.3V, 5V, 12V.


    --
    Conor

    life, n.: A whim of several billion cells to be you for a while
  3. Archived from groups: alt.comp.hardware.homebuilt (More info?)

    "kony" <spam@spam.com> wrote in message
    news:im2ef0tuksea1kmia86hh411026j8cpoel@4ax.com...
    >
    > On Thu, 15 Jul 2004 20:25:53 GMT, "alpha_uma"
    > <none_such@home.com> wrote:
    >
    <snip>
    >
    > >
    > >Would it be insanely messy to derive all the power lines needed for the
    ATX
    > >power plug on the motherboard from the laptop power brick? All
    suggestions
    > >will be greatly appreciated.
    >
    >
    > Yes, it would be messy... far easier, smaller, and maybe even
    > cheaper to just buy a ready-made solution.
    >
    > What you'd want is an LDO regulator for the 12V, and a step-down
    > switcher for 5V, 3V derived from that. You don't need -5V, -12V,
    > or 5VSB. These are sometimes integrated into single power boards
    > for use with Via miniATX et al.
    >
    > http://www.mini-itx.com/store/default.asp?c=10
    > http://www.logicsupply.com/product_info.php/products_id/204
    >

    Super! Thanks for the great links. These DC-to-DC converters are exactly the
    type of gizmos that I'm looking for.

    Are the ATX power plugs on miniITX motherboards identical with those on
    regular ATX motherboards? If the ATX power plug is identical, then I think I
    may be able to use these ready-made solutions for my microATX mobd. I'll
    need to get a good estimate of the max power I will need for my home-made
    box, and make sure that the DC-to-DC converter can handle it. In any case, I
    don't think I would be able to build one any better than what they are
    selling for only $86.00 (the price of their 120W model).

    Al-U
  4. Archived from groups: alt.comp.hardware.homebuilt (More info?)

    On Fri, 16 Jul 2004 01:56:18 GMT, "alpha_uma"
    <none_such@home.com> wrote:


    >Super! Thanks for the great links. These DC-to-DC converters are exactly the
    >type of gizmos that I'm looking for.
    >
    >Are the ATX power plugs on miniITX motherboards identical with those on
    >regular ATX motherboards? If the ATX power plug is identical, then I think I
    >may be able to use these ready-made solutions for my microATX mobd. I'll
    >need to get a good estimate of the max power I will need for my home-made
    >box, and make sure that the DC-to-DC converter can handle it. In any case, I
    >don't think I would be able to build one any better than what they are
    >selling for only $86.00 (the price of their 120W model).

    Tyipcally the miniITX are same ATX connector, but I vaguely
    recall hearing of one with different proprietary connector.
    Check specs on what you're buying, ask vendor if necessary or
    search the power supply model number on the 'net.

    120W is plenty for what you described, providing it has
    sufficient amps on 5V rail. Typical use on an ACPI-enabled
    operating system should be under 10A on 5V rail, though you might
    get it even lower if you used a compact flash IDE drive instead
    of the laptop drive. You might even be able to undervolt your
    CPU to shave a few more watts off... might be able to run it at
    around 1.35-1.45V. It's entirely possible whole system would
    run from a 60W PSU if it had correct rail amperage distribution,
    but certainly a higher wattage PSU is worthwhile to use whenever
    possible.

    One other consideration since it seems this is for an automobile,
    is that if your climate is very cold in winter you might find the
    electrolytic capacitors aren't doing so well. A solid aluminum
    replacement might be sought or possibly putting tantalums in
    parallel (attached to leads of original caps on back of
    motherboard), though tantalums don't die gracefully, do that at
    your own risk, after getting whole thing up and running stabily.
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