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Lights for scale boats

Discussion in 'Electronic Basics' started by JSchermeis, Oct 24, 2003.

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  1. JSchermeis

    JSchermeis Guest

    Help! I build radio controlled scale ships and boats as a hobby and need a
    circuit to operate the lights. Depending on the model, the main power is
    between 6 & 12v dc. I'm using 1.5v, 30mA bulbs, and need from 5 to 15 lights
    per model. The lights should operate at 1.3v for longer life and authentic
    appearance. I don't read schematics that well and have even less of a clue how
    to use it to make the finished circuit. But I could use about 10 of these in
    my projects. Any ideas?
    John
     
  2. Hi,

    Why not try something like this? (View in Courier)!

    -----
    O ----|78L05|-----------------------
    ----- | | |
    | (x) (x) (x)
    | | | |
    | (x) (x) (x)
    7-12V DC | | | |
    | (x) (x) (x)
    | | | |
    | (x) (x) (x)
    | | | |
    O-----------------------------------

    The x's are lamps and the 78L05 is a small 5V regulator that should be
    available from any electronics hobby shop. This will give you 1.25V per lamp and
    will take up any slack should you use a variety of supply voltages. You could use
    the 1A capacity 7805 instead without a heatsink as you will be drawing less than
    100mA. In fact, if you have the room, I would use the 7805 anyway.


    Cheers - Joe
     
  3. Rich Grise

    Rich Grise Guest

    Yes, I was about to suggest the same thing, except without the
    regulator. On a battery-powered boat, I'd think that you don't
    want to throw away any watts (which is what a regulator does) -
    just put the right number of bulbs in series for either a 6V
    or 12V system. I certainly wouldn't put in a universal light
    string, because once you've picked a battery for a given
    boat, it probably won't change.

    I'd also go for more than 1.3 as a target bulb voltage - it's
    amazing how much difference in light output there is for a
    very small change in voltage near its operating area. Say,
    1.4 ~ 1.45V. The important part, of course, is the current
    flow. John presumably knows to use matched bulbs, of course. :)

    The simplest thing would be to put 4 or 5 in series for a 6V
    system, and see which looks best, and 8 or 9 in series for a
    12V system. If you really want to fine-tune it, you could
    interpose some smaller resistance in series - even something
    like a car bulb - it wouldn't light, but it'd drop the voltage
    a little, so the bulbs will last longer.

    Good Luck!
    Rich
     
  4. An LM317 will give you 1.2V with the adj pin grounded, and if you use
    the regular 3 resistor circuit, any voltage above that up to its
    maximum.


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