12v lamp dimmer

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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

Re: 12v lamp dimmer



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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



Re: 12v lamp dimmer



"Tops"
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 ** 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






Re: 12v lamp dimmer



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



Re: 12v lamp dimmer



"Tops"
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**  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



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



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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.



Re: 12v lamp dimmer


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describe your lamp.
is 12V DC or AC?
regulated?
automotive?
what is to happen with neither input active?
what is to happen with both active?
how much are effort you prepared to spend getting the delay
is power for the lamp to come from the inputs or externally
how much power can the inuts provide?

Re: 12v lamp dimmer



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with a single output to an incandecant lamp, one
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when active would cause the lamp to light a
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intensity would also be nice.
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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


Re: 12v lamp dimmer


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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selector with a single output to an incandecant lamp, one
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when active would cause the lamp to light a
Quoted text here. Click to load it
60% intensity would also be nice.
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Re: 12v lamp dimmer


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Another approach is to use a 555 timer. power transistor, and a few
other parts.

"12 volt Lamp Dimmer"

http://ourworld.compuserve.com/homepages/Bill_Bowden/page6.htm#dimmer.gif

-Bill


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