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.
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
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?
Hello Tim, have a look at this article. I think it will do what you want with a modification or two.
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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.
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
selector with a single output to an incandecant lamp, one
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