Christine Headlights??????

[packman]

Does anybody know how to make the headlights of a car or truck slowly illuminate? Like in the movie "Christine." I always thought that was bad ass and been wanting to do that to one of the cars for a long time. It must be some sort of delay switch or something. I am not an electrician so I don't know what to look for.


Packman

[P72Ford]

I think you could install a rheostat and make the headlights dim or bright manually. Then again, it'd kind of suck to manually turn your lights on so that they looked like Christine's lights. Perhaps soemthing that slowly allows the voltage to creep up?

[Tiggie]

A large capacitor like from a stereo would prolly fo the trick. Seems to me it slowly light the lights as it filled if you wired correctly.

[P72Ford]

The capcitor might work. However, I though they have a rapid discharge. If thats the case, then it'd probably turn the lights on too fast. Also, what happens once the charge stored up is discharged? Would the lights go out then? How long does it take for the capacitor to charge up again?

[85crownHPP]

A capacitor doesnt work that way - juice does not flow from the positive side to the negative side, it only stores rapidly-dischargeable current on the positive side. So, anything wired to the positive side doesnt even get affected by the capacitor as far as turn-on is concerned.
The headlights would turn on just as fast, but they would turn off slow(er) than normal. Probably not slow enough to notice...

[Tiggie]

Then I guess the rheostat would have to do it. Don't they build a lot of heat when lots of juice flows threw them?

[Nathan in MI]

Yeah. Don't do a rheostat.

[86VickyLX]

Does anybody know how to make the headlights of a car or truck slowly illuminate? Like in the movie "Christine." I always thought that was bad ass and been wanting to do that to one of the cars for a long time. It must be some sort of delay switch or something. I am not an electrician so I don't know what to look for.


Packman

Didn't they slow down the film for that? I always liked that movie and the headlight effects are creepy and I would like to do that to my car.

[gadget73]

A capacitor doesnt work that way - juice does not flow from the positive side to the negative side, it only stores rapidly-dischargeable current on the positive side. So, anything wired to the positive side doesnt even get affected by the capacitor as far as turn-on is concerned.
The headlights would turn on just as fast, but they would turn off slow(er) than normal. Probably not slow enough to notice...

If you wired it in series, you could get them to light full bright, and fade out slowly but thats also not terribly useful. Once the cap hit full charge, no lights no mo. I charge the cap in my car this way though an 1156 bulb to keep it from sparking.

[Blackened300a]

Just hook them up to a dimmer switch and do it manually for the effect.

[86GmLsCoupe]

It's like theater dim on the newer cars in reverse. You think there'd be a way to hack a theater dim module from a car at the the junkyard and use it for the headlights?

[boXman]

Just hook them up to a dimmer switch and do it manually for the effect.

.......

[GoodSamaritan]

A dimmer switch, such as you would find in a house, won't work. It only works on ac by chopping the tops off the 120vac 60hz waves.

You need some sort of variable speed controler for a dc motor. One thing to remember, headlights draw a lot more current than most people think, so you would need to hook an amp meter up between the battery and the headlights to see how much they draw, before sizing the speed control.

Just for illustration, lets say one of your high beams draws 60watts. (I don't know the real number, just pulled that one out of thin air, because of all the 55watt off road lights , but 60 makes the math work out a even so it should be close enough for illustrative purposes)

60 watts / 12 volts = 5 amps

Just for the sake of argument here, lets say all 4 headlights combined draw 120watts.
Most common resistors are only rated for 1/4-1/2watts.



Using any type of resistor (aka rheostat or potentiometer) to soak up some of the current going to the lights would dim them, but the resistor would have to be huge and would heat up a lot.

Lets say you want to dim your headlights from 120watts down to 20 watts. Now you have dimly glowing headlights glowing out front, at 20 watts, but the other 100 watts hasn't gone away. Most of it is now heating up your rheostat.

Now we still have the problem of getting the right amount of resistance. at 12volts and 120 watts, the headlights would have a combined resistance of 1.2 Ohms. If you want to drop that all the way off and all the way back up to full power, you would need a rheostat that would go from 0.0 Ohms to about 25-30 ohms.

Lets look at the math

120 watts / 12 volts = 10 amps
12 volts / 10 amps = 1.2 ohms

If you wanted to drop them all the way down to around 5 watts...

5 watts / 12 volts = .4 amps

12volts / .4 amps = 30 ohms



Of course all these numbers would change if the headlights turned out to be more than 120 watts. Which they will.



The beauty of going with a dc speed controller, is you can use a tiny potentiometer to control it, and the thing won't heat up much.

[CheeseSteakJim]

Wow, who would've thought this would've been so complicated.

[Nathan in MI]

Ohm's Law is complicated?