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Thread: My new Sproggy style power supply

  1. #11
    FLAC Mastero's Avatar
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    jeez some in this world know me ... cool to know that!

    no it was not with load ... check this page its cool you can get 7.5 amps at 5v rail
    http://www.linear.com/prod/datasheet...t_family=power

    Let me know wat you think!

    MAstero

  2. #12
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    Yeah, looks good, but your probably gunna need a nice sized heatsink...

  3. #13
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    shall try to make one 5vdc supply and power somthing with it (any suggestion)

    and see how it works.

  4. #14
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    you could try powering a couple of 6v globes, I have some that draw like 4amps...
    okay, now that is really getting off topic, have to go now...
    post at ya later...

  5. #15
    Maximum Bitrate Raas's Avatar
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    Mastero, you can use linear regulators, but you will need a big-***-heatsink.

    Example.
    You have a linear regulator which gives you 5a @ 5v.
    You are 'feeding' this regulator with 12v
    All the volts present that is to much will be converted to heat.

    So you will end up with 12v - 5v = 7v
    5a @ 7v = 35w of pure heat !!! you have to find a way to get rid of this heat (heatsink)
    Also.. a linear regulator is much less efficient..
    You need like 5a @ 5v = 25w
    heatsink takes 5a @ 7v = 35w
    To supply the 5a @ 5v you will still pull 5a @ 12v from the battery, which makes it like 40% efficient.., now that isn't much is it, But it should work.... only have to remember some things from the back of your head.

    Hope this helps you out !

    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. #16
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    yeah and since we are wanting to design this power supply instead of using an inverter is mainly because of the innefficiency of using an inverter (at least for me), and having a greater control and greater range of voltage inputs... linear regulators will burn off more than half of the power drain in heat, which might be OK if you want to heat your car, but is wasting a lot of power.

    and Skinnyboy, I can't see your design! can you repost it, or post an URL?

    And no, you don't need permission, but you should probably give Sproggy a heads-up or ask him anyways, and be certain to release the specs since this is essentially an "open source power supply"

    Right now I'm investigating the possibility of how to easily use a normal power supply, because I wanted to kill one anyways to get all of the cables and wires and some parts, but if I can easily adapt It and then get a full 300W or so, why not (especially since it's cheaper than making the sproggy PS!)
    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.

  7. #17
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    oh and Skinnyboy I think you're right, I was wanting to add an extra 12V rail anyways, so perhaps I can just integrate that into the 2.7.2 design, or use yours.
    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.

  8. #18
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    Yeah, well that one I posted before was messy, so I have fixed it up and uploaded it again, you can also get the .TIF which you will need to use for actually size printing..
    http://www.geocities.com/bob_in_car_...nnyBoy_PCB.tif


    Yeah, tis all good???

  9. #19
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    Unforuntately, Skinnyboy, that design won't work. You've not only severed the +12V feed to the +3.3V output (which I suppose you might bridge instead), but you've also placed components right in the middle of the heatsink.

    The reason why I left that 1.5" between the bottom half and the top half was for the heatsink that will be needed to cool the power regulators.

    Also I don't see how you plan to join the two +12V outputs (unless you want the seperate).

    The original reason why I didn't bother with the second +12V rail was because there is only 1 component that will really draw any power off of that circuit, and that's the hard drive. If you plan on using a CD-rom drive as well then you might be in a bit more trouble. Any fans can be run straight off the mains because they're not very picky as to the input voltage that they receive (actually, even the hard drives are designed to work between +10.8V and +13.2V).

    If we wanted the second +12V rail, I think that we'd need to move all of the +12V rails to the top portion, and move the +3.3V rail back down. However this is seeming very silly to me. We have between +9V and +15V input, and we're using something that can only give us 1.2A on the +12V output? There *must* be better parts that we can use to get more than 1.2A off the +12V output.

    I haven't checked to see if the components will line up properly other than that, you'll have to draw up a component placement, but since we know that it can't work like that anyways, I'll see what I can do to redesign.

    However I'm not quite certain that this plan is worth sticking to anymore. Normal power supplies take the input voltage, convert it to +17VAC (I think) to power the rest of the devices. If we can just whip up something to convert the +9 to +15VDC input from the car to +17VAC at a decent power level, it would be much easier to do that, and then we can just reuse the rest of the power supply, which will not only give us a lot more power output, but would also be a lot easier to make. I'm looking into this possibility right now.
    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.

  10. #20
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    hey telek buddy hows u ...

    I was checking for some component for the 12v rail which can give more than 3amps .. i think LM2587-12 yup the same one can give us 5amps but in boost mode .... yup go to the national site they have the spec im woking on the converstion ! to - v


    mastero

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