Any ideas on how to transform my interior lights to

[aabdelhamid]

perform like the late models, I mean the dimming effect not simply on-off. Does this include any major changes or is it impossible.

[bahnstormer]

like when u close the door at night the lights fade off/out?

[aabdelhamid]

I need the dimming effect at night, way cool

[best535iever]

Hey great idea. Id love to do the same. It cant be impossible. Nothings impossible.

[George M]

yeah its completely impossible...lol...its just a relay. The best thing you can do with your interior lights is be seasonal. Around the beginning of December or so, I retrofit mine with twinkle lights to get in the Christmas spirit. Next I am considering mounting a small tree on the dash board but I am concerned about the water spilling out of the base during high speed cornering.
Your mileage may vary.
George

[best535iever]

So all you do is just replace relays? Sounds very simple. Shouldnt be expensive at all.

[bimmerd00d]

uhhh not that easy, it's gotta be a relay, and a series of resistors and capacitors. Where are the electrical gurus here?

[Dan in NZ]

If you added in a capacitor to the circuit, the lights would fade out when they are turned off, instead of turning straight off.

[Paul_540i]

Hi everyone, just registered. I recently picked up a nice 1995 540i 6sp manual (rare option over here in the UK).

In answer to your question, it can be done with a simple resistor-capacitor circuit in theory, but this would require quite a large capacitor and is not the way the standard systems work.

Likewise a relay wouldn't work on its own, it's simply an on-off switch (for isolating two circuits and switching larger currents etc).

What you need is a small controller that pulses the light on and off quickly. This gives the appearance of dimming as neither the bulb filament nor the eye react quickly enough to discern the cycles, it just appears dimmer. This is known as pulse width modulation. If you vary the ratio of the on and off periods, you can achieve full control of the brightness. 100% is fully on, 0% fully off, 50% half brightness etc. This is called the duty cycle.

You then vary the duty cycle such that when the light goes off it drops from 100% to 0% over several seconds giving the appearance of the light fading out.

I done a very similar thing with a previous car, it does look very nice. What you need is some kind of electronic controller to implement this. I used a PIC chip (a 16F627 with the appropriate code programmed into it), interfaced with some simple components so that it knows when the light input goes on or off. It then controls the light via a pair of transistors, to allow the high current of the light to be switched by the low current drive of the pic chip output.

I was planning on looking into this very thing on my e34. I haven't yet had time to check out the wiring setup, it's quite unusual in that the switch for the light in the front of the car also controls those in the rear. So there's obviously some connection there. Will let you know if I manage to get round to it successfully.

Cheers
Paul.

[Paul in NZ]

check out the wiring setup, it's quite unusual in

welcome to the club Paul I am sure you will meet Javier soon...............