Dimmer switch on fogs

rcanpolat · 21-06-2014 3:53pm #1

So I have a civic and it came with these fog lights (aftermarket JDM style) that the last dude put into the car. I like them but I find the light is very strong coming off them.

So...

Is it possible for me to wire up a potentiometer to them to reduce the amount of juice flowing into the lights making them dimmer?

Im fine with soldering etc but I don't know really know too much about electronics. I'm worried about wiring one up... With 12v flowing through it and god knows what current could it heat up and melt my center console in the car?

My only experience with potentiometers is rewiring my electric guitars and their volume and tone pots. I've never dealt with direct current in a potentiometer.

Any suggestions?

gctest50 · 21-06-2014 4:07pm

An ordinary potentiometer like in your guitars would melt

If the fog lights are plastic (ie not grounded ) you could wire them in series instead

visual · 21-06-2014 5:11pm

Change the bulb to the desired wattage is the simple solution.

rcanpolat · 21-06-2014 9:30pm

my fogs are metal so they are grounded. would you know what kind of potentiometer i would need?

i would change the bulb to a lower wattage but the day i run into thick fog i would like to be able to boost the light for better cut through

colm_mcm · 21-06-2014 9:37pm

But surely if you use them only when there is fog, and not when there isn't fog there is no issue?

gctest50 · 21-06-2014 10:06pm

rcanpolat wrote: »

.........
would you know what kind of potentiometer i would need?

A potentiometer is not the best way of going about it

When the lights are at say half-brightness it will "dump the excess" as heat

You could use PWM ( pulse-width-modulation )

Basically it turns the lights on and off really quickly

Obviously the more "on" time , the brighter the light

The unit won't get so hot because it is just turning the lights on or off

Jeep and a few more use it apparently

https://www.youtube.com/watch?v=T5dh9iXOaRc

visual · 22-06-2014 12:11am

gctest50 wrote: »

A potentiometer is not the best way of going about it

When the lights are at say half-brightness it will "dump the excess" as heat

You could use PWM ( pulse-width-modulation )

Basically it turns the lights on and off really quickly

Obviously the more "on" time , the brighter the light

The unit won't get so hot because it is just turning the lights on or off

Jeep and a few more use it apparently

https://www.youtube.com/watch?v=T5dh9iXOaRc

Jeep use it to control the electric fan but I wouldn't recommend it for fog lights

gctest50 · 22-06-2014 12:16am

Wouldn't want to use it unless you know what yer at - easy for it to annoy the ABS / fuel injection and kill you

gctest50 · 22-06-2014 12:27am

visual wrote: »

Jeep use it to control the electric fan but I wouldn't recommend it for fog lights

Volvo used it for lighting stuff, keeps the bulbs at a happy 13v

visual · 22-06-2014 12:41am

rcanpolat wrote: »

my fogs are metal so they are grounded. would you know what kind of potentiometer i would need?

i would change the bulb to a lower wattage but the day i run into thick fog i would like to be able to boost the light for better cut through

if your using standard bulbs that is 110W
your potentiometer would be the size of a large transformer and would get very warm.

you really need to read up about fog lights its not about high power to cut through the fog.

Fog lights in some cars are rated as low as 35w while in others its 55w and there is some in-between at 45w

the fog light is angled down and doesn't extend as far in front as your dip head lights but has a wider beam side to side than dip beam lights.
This is to stop light being reflected back of fog and into your eyes reducing visibility. Its also the reason you don't use high beam in fog.

I have seen spot lights that have a small 5w bulb that lights up as a marker light when cars side lights are on and a second 55W bulb for when the spot light is on. maybe you could do that
or as gctest50 suggested build a PWM circuit

http://www.jaycar.com.au/productView.asp?ID=KC5225

but I wouldn't recommend going to all that trouble unless your big into electronics

visual · 22-06-2014 12:44am

gctest50 wrote: »

Volvo used it for lighting stuff, keeps the bulbs at a happy 13v

forgot about the internal dome lights in Jeep they also have auto dimmer and timer

rcanpolat · 22-06-2014 10:32am

visual wrote: »

if your using standard bulbs that is 110W
your potentiometer would be the size of a large transformer and would get very warm.

you really need to read up about fog lights its not about high power to cut through the fog.

Fog lights in some cars are rated as low as 35w while in others its 55w and there is some in-between at 45w

the fog light is angled down and doesn't extend as far in front as your dip head lights but has a wider beam side to side than dip beam lights.
This is to stop light being reflected back of fog and into your eyes reducing visibility. Its also the reason you don't use high beam in fog.

I have seen spot lights that have a small 5w bulb that lights up as a marker light when cars side lights are on and a second 55W bulb for when the spot light is on. maybe you could do that
or as gctest50 suggested build a PWM circuit

http://www.jaycar.com.au/productView.asp?ID=KC5225

but I wouldn't recommend going to all that trouble unless your big into electronics

I checked yesterday, bulbs are 12v 55 watt halogen. What about moving to led and then using a potentiometer. No difference?

Dimmer switch on fogs

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