bulb dimming using resistor

Hey guys, trying to figure out how to dim a 194 wedge bulb that I have to half the brightness. Basically I'm making a circuit so that the bulb will always be on at half brightness, but blink at full brightness. For diodes, all I would need is the usual 1N4001 correct? But for the resistor, not sure what I should use. I know I'm going to use a 100 ohm resistor since it is closest to cutting the resistance of a bulb at .27 amps at 14 volts, which has 51.851 ohms of resistance. Now 100 ohms of resistance at 14 volts equals .14 amps, and 1.96 watts of power dissipation. Now even with a 5% tolerance, that could mean the power dissipation could be as much as 2.058 watts which puts it over 2 watts. EDIT- Here is a diagram of what I think is right... Correct me if I am wrong as I am still learning but you are supposed to use a resistor with a higher wattage than that of what it is dissipating, right? If that is so, I think radio shack only carries 100 ohm 10W 5% wirewound resistors. Would that still be ok to use? If I'm completely screwed up on all of this, can someone please help me out? I'd really appreciate it! THANKS!Eclipse 8445, Kicker DS60's, Hifonics TXi4400, Eclipse SW6143DVC, and Power Acoustik LT980-2.

If I understand correctly, you want the bulb to be at half brightness when parking lights are on and you want it to blink at full brightness when the blinker blinks, is this correct?

i am an idiot wrote: If I understand correctly, you want the bulb to be at half brightness when parking lights are on and you want it to blink at full brightness when the blinker blinks, is this correct?

Hit the nail on the head, this is correct!Eclipse 8445, Kicker DS60's, Hifonics TXi4400, Eclipse SW6143DVC, and Power Acoustik LT980-2.

You need to ditch the resistor on the blinker wire. If it is resisted also it will make very little if any difference when the blinkers blink. No resistor = full bright when blinking. You will have to play around with the resistor values to get your desired brightness. 100 ohms in series with a 51 ohm resistor (if the bulb stays at 51 ohms when heated) would cut 2/3 of the power. The bulb would get 1/3. I didn't check your power consumption math, but if you use the 5 watt resistor you will be more than fine. You may have to parallel 2 resistors to get what you want. Try with 1 if not bright enough use the second one also. If with one resistor it is too bright, connect the second one in series for a total of 200 ohms resistance before the bulb. This may or may not even attempt to light the bulb.

Yea I did screw up on my diagram, yes, no resistor on the blinker wire. The bulb at full brightness at 14v, draws .27 amps with 51.851 ohms of resistance. To cut that current draw in half, then I need to have about 100 ohms of resistance, so I don't double that into a resistor right, instead I add another 50 ohms of resistance to kick up the resistance to ~100 ohms. Am I understanding this correctly?Eclipse 8445, Kicker DS60's, Hifonics TXi4400, Eclipse SW6143DVC, and Power Acoustik LT980-2.

Yes you are undersanding it correctly now.

i am an idiot wrote: Yes you are undersanding it correctly now.

Thanks for the help, to radioshack it is!Eclipse 8445, Kicker DS60's, Hifonics TXi4400, Eclipse SW6143DVC, and Power Acoustik LT980-2.

I went and got the resistors yesterday, they are 50 ohm wirewound 10W 10% tolerance, they didn't have 5W ones. I hooked it up, and not sure if I like it or not... But I will tell you one thing, I am glad I asked, because had I gotten 100 ohm I would have been kicking myself! Thanks I am an idiot, very helpful.Eclipse 8445, Kicker DS60's, Hifonics TXi4400, Eclipse SW6143DVC, and Power Acoustik LT980-2.

Glad to help you, but what about are you not sure you like?