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12v lamp dimmer

Discussion in 'Hobby Electronics' started by Qwerty, Dec 10, 2005.

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  1. Qwerty

    Qwerty Guest

    I am looking for a circuit that I can take 2 different 12v inputs as a selector with a single output to an incandecant lamp, one
    input would output a reduced voltage to the lamp (say 60%) and the other input when active would cause the lamp to light a
    100% of it intensity. A bit of a delay (say 1-2 sec) when switching back to 60% intensity would also be nice.

    Any thoughts, suggestions, diagrams???

    Thanks for any help.
    Tim
     
  2. Tops

    Tops Guest

    If the circuit is AC the energy to the bulb on one circuit could be reduced
    significantly by putting a diode in the circuit to eliminate one half of the
    AC waveform. Cheap and simple
     
  3. Phil Allison

    Phil Allison Guest

    "Tops"

    ** The stepdown transformer would be very unhappy about the load with a
    diode in series.

    It will growl and overheat - especially if a toroidal type.




    ........... Phil
     

  4. Hello Tim,
    have a look at this article.
    I think it will do what you want
    with a modification or two.
    http://www.solorb.com/elect/solarcirc/pwm1/

    For two fixed lamp brilliance settings
    you could make VR1 a normal fixed resistor
    and use a change over switch to select the
    top end or bottom end of this new resistor.

    Or you could make a second voltage divider
    R6 VR1 R7
    and use a change over switch to select either
    one wiper or the other wiper.

    To get the slow change in lamp intensity
    after switching, you could fit a resistor between
    the wiper of VR1 and Pin 6 of U1b along with
    an electrolytic cap on Pin 6 to Ground.
    Experiment with different values to get the
    desired delay in lamp intensity change.

    Regards,
    John Crighton
    Hornsby
     
  5. Tops

    Tops Guest

    What would be the best way to do this Phil while keeping the cost as low as
    practical.
    P_R.
     
  6. Phil Allison

    Phil Allison Guest

    "Tops"


    ** You did not answer my point - fuckhead.

    The OP has not specified the details his actual problem - not that a lying,
    know nothing criminal scumbag from Maitland like you would notice.




    ......... Phil
     
  7. Tops

    Tops Guest

    Phil, all I can say to your unprovoked outburst is..you certainly have a
    very significant problem.
     
  8. Phil Allison

    Phil Allison Guest

    "Tops"


    ** Like fucking hell it was "unprovoked".

    Piss off - you steaming pile of criminal libelling scum.



    NB This arsehole is known to me from another NG.



    .......... Phil
     
  9. Tops

    Tops Guest

    Gee, we really are belligerent tonight, aren't we Phil. Totally unrestrained
    with the vitriol as per usual.
     
  10. Tops

    Tops Guest

    What is your point, Phil. You could be giving a constructive answer to the
    original poster's issue instead of going on like a pork chop.
     
  11. Phil Allison

    Phil Allison Guest


    ** Drop dead.
     
  12. Qwerty

    Qwerty Guest

    Thank for you for the link, I will check it out. :)

    To answer some questions:
    unregulated - will vary from approx 11.5-14.5v
    DC operation
    both inputs are from the same source but connected to 2 different switches:
    - one switch most likely always on will be at the reduced intensity
    - 2nd switch will only activate as needed and provide 100% intensity.
    - 2nd switch is connected to a flasher circuit, hence the delay as I would like the lamp to turn off between flashes for more visual impact.

    thanks again for the quick replies.
    Tim
     
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