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2005 SLK200K
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326 Posts
Discussion Starter · #1 ·
There are two problems with simply changing the footwell ( and door access lightbulbs) to white LED bulbs.
1. when driving, they are dimmed by the car cpu, but they remain white, which is not in theme with the rest of the car interior accent lighting which is amber. The central console lights are lit amber. There is even an amber LED underneath the rear view mirror to subtly accentuate the dashboard amber.
2. They are dimmed but they are still too bright. The cpu cannot control the LED very well. They are a bit distracting to me. I notice my feet all the time when I drive.

for me its ok that the map lights, vanity lights glove compartment lights and others are white LED and bright. They are functional and you are indeed wanting to see or read something when you activate them. Footwell lights for me should be amber when dimmed (and are functioning as accent lights) and bright white when you are getting out of the car as they are acting as safety lights.
i had nothing better to do this easter weekend. Here is a simple bulb you can make that does exactly just that. i used a very common left over 5V RGB LED strip. 2 LEDs. Schematics are shown and lots of pics on how I built them. They work very well. Also they are properly dimmable. Components can be bought from you local electronics hobby shop. In Australia thats usually Jaycar or even Ebay.
For those who appreciate electronics read on. Else go ahead an see the pics and schematics. Some soldering skill is needed:
the reason LEDS dont dim very well is because, like most control circuits, the cpu uses PWM to dim the lights. LEDs use so little current that current is difficult to control. The diode resistor and capacitor in the input converts PWM into an actual steady voltage. When duty cycle is low (cpu is trying to dim the light) voltage on the capacitor is just enough to turn the red LED on and very very slightly the green one (which has to contend with one extra diode drop). Red + dim green = Amber. The blue LED does not turn on because its activation voltage is in the 3.2V area, plus the extra diode drop. The red led whose voltage drop is at 2.8V ensures this doesnt happen. (Green LED on voltage is 3V, it turns on very slightl, just enough to get an amber color). When duty cycle is high, voltage on capacitor reaches 8 volts and higher, ensuring all 3 colors light up which produces a white light, The 180ohm resistor is there simply to draw current as for whatever reason, the cpu shuts off the power if too little current is drawn.

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2005 SLK200K
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326 Posts
Discussion Starter · #2 ·
It occurred to me that I never posted the results of the work. Here they are 1 year later. Still very nice.
Automotive lighting Gesture Font Electricity Midnight

thats how the footwell lights look like when doors are closed. LEDs are properly dimmed. Color in real life is closer to the amber dials. (The iphone is doing some automatic white balancing.) The footwell lights match the amber accent lights and dials.

Vehicle Car Motor vehicle Automotive design Gear shift

here’s what it looks like when the car has stopped and you remove they keys to get out fo the car. The footwell lights are bright and white, it matches the white LEDs i replaced all over the car. (No flash was used in this photo).
 

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2012 SLK200
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165 Posts
Would a SMD MLCC Multilayer Ceramic Capacitor work as well?
Also I asked about a switching device ( perhaps loaded into an eeprom ) from orange to light blue to use the circuit in other cars.
 

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326 Posts
Discussion Starter · #8 ·
Would a SMD MLCC Multilayer Ceramic Capacitor work as well?
Also I asked about a switching device ( perhaps loaded into an eeprom ) from orange to light blue to use the circuit in other cars.
If you use a cpu to control the lighting the price would go up considerably. Target retail price is about 10 bucks a piece.

its easier to just make a blue light/white light version I think. For the circuit I have provided, thats really simply playing around with the diodes ( connect them to the red LED instead of the blue) and adjusting the resistances to taste.
 

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Discussion Starter · #9 ·
They are finally here! If you don’t feel like doing the DIY, you can buy the circuit ready made. I’ll put it up on ebay. But before that I will send some samples to my favorite members down under. (Mostly to save on shipping costs).
Rectangle Font Auto part Metal Fashion accessory

Font Fashion accessory Auto part Metal Titanium

Automotive lighting Circuit component Rectangle Hardware programmer Computer hardware

I put a variable resistor on this version so you can dim the amber LED further to your preference. Its an accent light after all and in my opinion it should very subtlety light up the footwell when driving. Noticing your feet when you drive can be a bit distracting.
 

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*Registered
2005 SLK200K
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326 Posts
Discussion Starter · #10 ·
Would a SMD MLCC Multilayer Ceramic Capacitor work as well?
Also I asked about a switching device ( perhaps loaded into an eeprom ) from orange to light blue to use the circuit in other cars.
I think so, but it might be tough to get a 47uf value. To be safe you want this to be at least 25V tolerant.
 

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2009 SLK55 AMG w/P30
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There are two problems with simply changing the footwell ( and door access lightbulbs) to white LED bulbs.
1. when driving, they are dimmed by the car cpu, but they remain white, which is not in theme with the rest of the car interior accent lighting which is amber. The central console lights are lit amber. There is even an amber LED underneath the rear view mirror to subtly accentuate the dashboard amber.
2. They are dimmed but they are still too bright. The cpu cannot control the LED very well. They are a bit distracting to me. I notice my feet all the time when I drive.

for me its ok that the map lights, vanity lights glove compartment lights and others are white LED and bright. They are functional and you are indeed wanting to see or read something when you activate them. Footwell lights for me should be amber when dimmed (and are functioning as accent lights) and bright white when you are getting out of the car as they are acting as safety lights.
i had nothing better to do this easter weekend. Here is a simple bulb you can make that does exactly just that. i used a very common left over 5V RGB LED strip. 2 LEDs. Schematics are shown and lots of pics on how I built them. They work very well. Also they are properly dimmable. Components can be bought from you local electronics hobby shop. In Australia thats usually Jaycar or even Ebay.
For those who appreciate electronics read on. Else go ahead an see the pics and schematics. Some soldering skill is needed:
the reason LEDS dont dim very well is because, like most control circuits, the cpu uses PWM to dim the lights. LEDs use so little current that current is difficult to control. The diode resistor and capacitor in the input converts PWM into an actual steady voltage. When duty cycle is low (cpu is trying to dim the light) voltage on the capacitor is just enough to turn the red LED on and very very slightly the green one (which has to contend with one extra diode drop). Red + dim green = Amber. The blue LED does not turn on because its activation voltage is in the 3.2V area, plus the extra diode drop. The red led whose voltage drop is at 2.8V ensures this doesnt happen. (Green LED on voltage is 3V, it turns on very slightl, just enough to get an amber color). When duty cycle is high, voltage on capacitor reaches 8 volts and higher, ensuring all 3 colors light up which produces a white light, The 180ohm resistor is there simply to draw current as for whatever reason, the cpu shuts off the power if too little current is drawn.

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I guess I am too dumb to notice but I changed both the foot well and pool bulbs under the doors with appropriate LEDs from Amazon per Jeff's warnings. When the door is open the footwell is well illuminated and when driving they are dim. Can't comment on the door lights as I only see them at night as a rule just as the OEM bulbs were. I don't see the interior theme as being Amber. It is just the lighting that came from the OEM bulbs. All my interior lights are LED as is my trunk.
 

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Discussion Starter · #12 ·
I guess I am too dumb to notice but I changed both the foot well and pool bulbs under the doors with appropriate LEDs from Amazon per Jeff's warnings. When the door is open the footwell is well illuminated and when driving they are dim. Can't comment on the door lights as I only see them at night as a rule just as the OEM bulbs were. I don't see the interior theme as being Amber. It is just the lighting that came from the OEM bulbs. All my interior lights are LED as is my trunk.
the LED lights do dim but only a bit, I bet you can still see your feet clearly while driving. This might be distracting to some. The intention of MB when dimming the footwell lights is to create a barely perceptible amber glow in the footwell, just for accent lighting really. If you notice that all the dials in the console and steering wheel are lit in amber. Try to look underneath your rear view mirror, there is also an amber LED there to accent the dashboard amber. The only things that are white are the Audio20 center display and the speedometer/RPM areas.
The original incandescent bulbs fitted in the footwell did just that. It dimmed properly (Some owners didnt even notice it until they changed those bulbs to LED) and it is naturally amber (as all incandescent bulbs are).
When you changed that bulb into an LED (most likely white) it did not dim properly anymore and it stays white. (I always notice my pale legs when I drive and its distracting).
The problem with keeping incandescent bulbs in the footwell is that they dont light up too bright when needed.
In the end its what you prefer anyway. This DIY really is more for fun than for any real important function. :)
 

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2009 SLK55 AMG w/P30
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the LED lights do dim but only a bit, I bet you can still see your feet clearly while driving. This might be distracting to some. The intention of MB when dimming the footwell lights is to create a barely perceptible amber glow in the footwell, just for accent lighting really. If you notice that all the dials in the console and steering wheel are lit in amber. Try to look underneath your rear view mirror, there is also an amber LED there to accent the dashboard amber. The only things that are white are the Audio20 center display and the speedometer/RPM areas.
The original incandescent bulbs fitted in the footwell did just that. It dimmed properly (Some owners didnt even notice it until they changed those bulbs to LED) and it is naturally amber (as all incandescent bulbs are).
When you changed that bulb into an LED (most likely white) it did not dim properly anymore and it stays white. (I always notice my pale legs when I drive and its distracting).
The problem with keeping incandescent bulbs in the footwell is that they dont light up too bright when needed.
In the end its what you prefer anyway. This DIY really is more for fun than for any real important function. :)
If you are driving you should not be looking at your feet!🤣🤣🤣
 

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2014 SLK250
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401 Posts
some led lamps are fixed (eg the 2 large illuminators under the rearview mirror)

so in my case i had to color match to those and moderate intensity 4000k led units worked well including the (partial) dimming action
 
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