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24vdc to 12vdc

Discussion in 'Electronic Basics' started by Chris Serra, Aug 2, 2003.

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  1. Chris Serra

    Chris Serra Guest

    Hi all. I have a pretty simple question. I am looking at reducing 24vdc to
    12vdc. I am new to making circuits, but I fix video games for a living, so
    I know my way around most pcb's. I am not sure the best way to do it, using
    resistor, caps, or if a simple 7812 will do the trick. I am not looking for
    someone to make the circuit for me, but just nudge me in the right
    direction.


    Thanks alot.

    Chris Serra
     
  2. tempus fugit

    tempus fugit Guest

    7812
     
  3. A couple of 5w 10 ohm resistors and a unijunction transistor would be more
    of a challenge with a 10 ohm pot off the collector of the unijunction
    transistor. (assuming the 24vdc potential has less than 503 ma of current
    and ignoring the 12v zener hanging off the emitter going to "ground" the
    negative pole) But then, I digress...

    24vdc to 12vdc
     
  4. Blake

    Blake Guest

    There are two options - a linear or a switcher. A linear (7812-type)
    solution will dissipate power equivalent to 12V (the amount dropped) times
    the current your load will draw. With a big heatsink, you can drop a lot
    of power. You will have to do the math to be sure that the 7812 will not
    get too hot.

    A switcher will dissipate a lot less heat, maybe 5-30% the heat of the
    linear. There are some small switchers that you can drop in that are easy
    to design because the datasheet spells out what to do. But a divide-by-two
    switcher can be as easy as a 50% duty-cycle switch followed by an LC
    circuit.

    Blake
     
  5. Leigh W3NLB

    Leigh W3NLB Guest

    We need to know the current drain: minimum, average and maximum, if
    it varies. Can't design a regulator until we know that information.


    73 de Leigh W3NLB
     
  6. Brian Lund

    Brian Lund Guest

    Hi all. I have a pretty simple question. I am looking at reducing 24vdc
    to
    It depends on how much current you need, the 7812 is often a good choice,
    but for circuits requiring a lot of current you need something else. You can
    get the as 7812 as a low power model, it is called 78L12 and can maximally
    deliver 100 mA.
    http://www.el-supply.dk/elpix/7B.GIF

    The regular (TO220) can deliver 1-1.5A depending on the manufacturer.
    http://www.el-supply.dk/elpix/17B.GIF

    And for high-power requirements there is a 3A model in a TO3 package.
    http://www.el-supply.dk/elpix/23A.GIF

    Always remember to use a heatsink for the later two models as they do get
    pretty hot when they have enough load.


    Brian Lund
     
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