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12v to 5v SMPS?

Discussion in 'Electronic Design' started by flash, Apr 1, 2006.

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  1. flash

    flash Guest

    Hey guys. I have been trying to figure this out for myself for ages,
    but have admitted defeat. What I plan on having is a 12v SLA (sealed
    lead acid) battery, but I need 5v out, to connect to a USB port to
    charge stuff like my phone mp3 player etc...
    I understand that it would probably need to be regulated, due to how
    SLAs discharge and what not.

    So what I would like to know is if I can buy a 12v to 5v regulated
    switch mode power supply, or will I have to make one up? If the latter,
    does anyone know what IC (I assume) I would need?

    Thanks a lot guys,
    Chris
     
  2. Genome

    Genome Guest

    YOU SCUM SUCKING PIECE OF **** YOU. COME IN HERE WITH YOUR 'HI GUYS' LIKE
    YOU THINK I REALLY NEED TO THINK THAT YOU THINK I'M GOING TO BE YOUR FREIND
    AND TELL ME ABOUT YOUR MP3 PLAYER LIKE YOU THINK I SHOULD REALLY BE
    INTERESTED AND THEN TELL ME ABOUT HOW YOU KNOW IT SHOULD BE WHATEVER. YOU
    PIECE OF SHIT. I DON'T NEED TO LOOK AT WHERE YOU LIVE, SOUTHERNER, WASTE OF
    SPACE AND WASTE OF GRAVITY. IT'S NOT AS IF THE TORIES FUCKED IT UP LAST TIME
    THEY ASKED THE THIRD REICH TO KILL OFF YOU FUCKING LONDONERS. LOOK YOU ****
    UP TWAT, YOU POSTED FROM GOOGLE SO WHAT IS YOUR FUCKING PROBLEM? CAN'T YOU
    GET IT TO SPELL BANANA FOR YOU?

    DNA
     
  3. Bob

    Bob Guest

    Chris,

    First, please ignore the idiot that has already responded. Anyone that
    spells friend as "freind" needs some serious help and schooling.

    Depending on how much current you need, you may be able to get away with a
    simple linear regulator (like a 7805). With this approach, you will waste
    (in watts) 7V * current draw.

    If this is too much wasted power (e.g., the 7805 would get too hot or the
    battery life would be compromised) then you must use a switching regulator.
    Digikey probably has one that will work, for you. Devices made by Artesyn,
    Power One, and Tyco come to mind.

    Bob
     
  4. Michael

    Michael Guest

    You might check out the integrated switching regulators of Power Trends (now
    part of Texas Intruments, I believe). For example, one 5v 1A unit ("EA" style)
    is pin compatible with the popular 5v 1A 7805 linear regulator that Bob
    mentioned; DigiKey sells it (part# PT5101N-ND) for $12.25. A data sheet is
    available from Texas Instruments site.
     
  5. Ian Stirling

    Ian Stirling Guest

    Not all USB devices will charge with simply +5V on a USB connector.
    Some of them need a USB host to talk to, to authorise them to draw
    This is actually the right thing for them to do, but causes problems
    with dumb chargers.
     
  6. flash

    flash Guest

    Oh cool. Thanks a lot for your help :) You've given me some ideas that
    I can go with. Also, the USB bit that Ian mentioned was something I
    hadn't considered.... I think I am going to build it and see how I get
    on..

    Thanks again
    Chris
     
  7. Guest

    There was a thread on the most simple sm regs. Just google for:
    regulator nt sm. In short you dont need any IC, just 2 trs and a few
    passives.

    NT
     
  8. Ian Stirling

    Ian Stirling Guest

    To meet [email protected]?
     
  9. flash

    flash Guest

    I have decided to use the chip PT5101, cant remember the letter after
    that, but it's the horizontal one. It should arrive here tomorrow, then
    I'll hook it all up and get back to you and let everyone know how I got
    on.

    It has a solar panel, which trickles charges a 6v SLA. Then there is a
    SPDT switch to switch between charging and dischaging. When set to
    discharging it will be connected to the PT5101 circuit (with the
    capacitor which is talked about in the datasheet for this component),
    which will give me 5V out. From here, there will be a female USB
    connector, so that I can connect my stuff in and hopefully charge it.

    Thats my plan :)

    Chris
     
  10. Guest

    ahh, usb port. It can be done, add a filter, tighten the v sensing, but
    I agree it would get more complex.

    NT
     
  11. Siong Boon

    Siong Boon Guest

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