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DC step up converter

Discussion in 'Electronic Design' started by 51_racing, Jun 26, 2006.

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  1. 51_racing

    51_racing Guest

    I'm looking at building, or actually having built, a step up converter
    to go from 12v DC to 16v DC, similar to this:
    http://www.auto-physics.com/ for racing purposes. Does anyone know where
    I might find a schematic to do something like this?

    Thanks.
     
  2. Joerg

    Joerg Guest


    Lots of marketing fluff but little data in that link. Like, how many amps?

    If you want to see how it's done in general look at the National LM3478
    data sheet.
     
  3. 51_racing

    51_racing Guest

    I really know very little about this stuff, and was planning on having a
    friend build it for me. I'm just the driver/mechanic for the car.
    It has a GM HEI ignition, 12 volt battery, no alternator, that's about
    all I can tell you, I have no idea on amps or how to find out even.
     
  4. Tim Wescott

    Tim Wescott Guest

    If that's your level of understanding, you'll spend a _lot_ of time
    learning, and probably lose quite a few races to equipment problems,
    before you get it right.

    Unless the quest for knowledge is what floats your boat just buy the
    module -- if it works right it's a bargain. If it seems expensive make
    a list of all the parts in your car, and how much it'd cost you to
    replace them, then add it up. Compare that to the cost of the module.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at http://www.wescottdesign.com/actfes/actfes.html
     
  5. Joerg

    Joerg Guest


    Then you need a friend who knows electrical engineering really well. The
    total amps can be measured and calculated. Mostly I guess it will be
    whatever the ignition system needs plus fuel pumps and whatever else is
    hanging on the 12V grid and used during a race (two-way radio etc). But
    watch out for stuff that will not tolerate 16V. The radio, for example,
    most likely won't.
     
  6. 51_racing

    51_racing Guest

    The person that is offering to build it is a master electrician, so he
    must have a fairly good handle on this stuff.
    Since this is a race car, the only electrical components on the car are
    the starter, ignition, and a couple of very small 12 volt gauge lights.
    I had planned to only run 16 to the ignition since that's the only place
    needed, but it could be the entire system. Some classes allow the use of
    16 volt batteries, but mine doesn't so I'm stuck looking for a solution
    such as this, and since I'm cheap, I'd rather build something than fork
    out the money for this.

    Thanks for the input so far everyone.
     
  7. Joerg

    Joerg Guest


    Just keep in mind that this is electronics and doesn't have much to do
    with what an electrician typically encounters. A switch mode converter
    requires quite a bit of know-how on circuit board layout, cross-talk and
    stuff like that.

    No idea how big this car is but it might not be too cool to feed the
    starter from your new 16V supply. That could fry the converter.

    Anyway, play it safe. Beyond a few amps this kind of circuitry can
    become dangerous. I have seen high powered switch mode converters fail
    in spectacular ways. Stuff flying around, molten solder, plastic shards etc.
     
  8. kell

    kell Guest

    If you can find a converter that does the same thing, but sold to a
    different market (not race cars), it would come quite a bit cheaper, I
    think.
    How about a four or five volt buck converter with an isolated output?
    I haven't looked for one, but maybe something's out there with the amp
    rating you need. You could simply put the output of the converter in
    series with the battery.
    And if you end up having your converter custom built, this approach is
    worth considering.
     
  9. Jim Thompson

    Jim Thompson Guest

    Just replace the wiring with Monster Cable ;-)

    Seriously, a better way would be to simply build a better CD Ignition.

    ...Jim Thompson
     
  10. Joerg

    Joerg Guest

    Hello Jim,
    However, that requires a whole lot more know-how than a boost converter.
    Maybe you friends at Bosch have something. But it won't be cheap.
     
  11. Rich Grise

    Rich Grise Guest

    So, you're trying to do a spark booster, on the cheap, because you think
    it will make your car go faster?

    Try dressing your plugs, and try a proper battery that's designed to last
    a race without being charged, like a boat or RV battery. For a hotter
    spark, there are things you can put in your plug wires that introduce
    an additional gap, such that when the coil voltage gets high enough to
    fire both arcs in series, it had built up much more energy from the
    inductive flyback. And, since they're in series, all of the current
    will flow through each.

    Good Luck!
    Rich
     
  12. ian field

    ian field Guest

    Since it probably isn't a good idea to increase theVsupply to an ignition
    unit that contains electronics already, it seems reasonable to assume the
    setup in question is the old faithful battery/coil/points type.

    One scheme I've had very good results with is simply a "grounded gate" high
    voltage MOSFET, the grounded gate is actually a bit of a misnomer since the
    gate is actually connected to +12V, it merely reflects the amplifier
    configuration as it would be in a normal circuit! The source terminal is
    connected to the points and the drain terminal is to the -ve of the coil.

    When the points are closed the source is held at 0V and as the gate is at
    +12V the MOSFET is fully conducting, the real clever bit comes at the
    instant the points separate. The MOSFET switches off very rapidly and
    eliminates the points gap arc that wastes energy and since the way it is
    wired to emulate the common gate configuration, the switching time is
    extremely fast! This adds to the amplitude of the spark at the plug.

    The only other addition is a clamp zener from +12V to source to protect the
    gate from any ringing, the modification gives a huge improvement at high
    revs but at low revs where the coil current duration is long enough for DC
    winding resistance to have greater effect than the coils inductance, the
    MOSFETs RDSon becomes significant, as a result the performance at very low
    revs is actually slightly less! Another known problem is cranking voltage, a
    typical high voltage power MOSFET will have a VGth of around 6 or 7V which
    can make starting a bit iffy on cold mornings if the battery isn't in tip
    top condition!
     
  13. 51_racing

    51_racing Guest

    Yes on the "spark booster" but I've already done all the basics. I can
    run a large gap on my plugs due to the aftermarket coil and module in
    the ignition system. The battery will pretty easily last two races
    without charging, that isn't the problem at all. What I'm trying to is
    supply the higher voltage which, with everything else, will create a
    hotter spark.
     
  14. Jim Thompson

    Jim Thompson Guest

    [snip]
    ONLY if it were a conventional ignition with points. An electronic
    ignition most likely has the electronic "smarts" to run constant
    energy.

    ...Jim Thompson
     
  15. 51_racing

    51_racing Guest

    Jim Thompson wrote:

    I believe my power cable is a 0 gauge, should be big enough!
    I agree on the CD ignition, I'd prefer to run a magneto if I could too,
    but my rules stipulate stock style ignition, which for me is a GM HEI
    electronic ignition.
     
  16. Jim Thompson

    Jim Thompson Guest

    GM? Fry baby, fry ;-)

    ...Jim Thompson
     
  17. 51_racing

    51_racing Guest

    Jim Thompson wrote:

    Actually, no. General motors HEI ignition systems work better at 16
    volts and start to lose energy when your battery drains below 11 or so.
    Since a car with an alternator will have 14+ volts running normally,
    that is what it would normally see, but since we don't run alternators
    we run into the problem of batteries draining.
     
  18. 51_racing

    51_racing Guest

    (knocking on wood) still on my first and only one of the year so far,
    but in the class I used to race in, I burned up 4 or 5 or them last year.
     
  19. Jim Thompson

    Jim Thompson Guest

    Thus my snide remark about GM ;-)

    (In the '60's I designed regulators, ignitions systems, turn signals
    and head-lamp dimmers for all of the American auto manufacturers.)

    ...Jim Thompson
     
  20. Jim Thompson

    Jim Thompson Guest

    Thus my snide remark about GM ;-)

    (In the '60's I designed regulators, ignitions systems, turn signals
    and head-lamp dimmers for all of the American auto manufacturers.)

    ...Jim Thompson
     
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