It's been a while since my last mod. It's not that I haven't performed any over the past months - I just didn't find the time to process the pictures and make a nice write-up. Anyway, here's another small modification I've performed lately. Once again it deals (partially) with the illumination of controls - more specifically the illumination of the power window controls.
The picture below shows the internals of the power window control unit. The buttons are illuminated by two orange colored incandescent light bulbs and transparent plastic light bars. Not all buttons are evenly illuminated. The buttons furthest away from the bulbs receive a lot less light than the buttons close to the bulbs. Most people may not even notice, but those who have been reading my topics know these are details that annoy me. The instruments and controls illumination in the E31 is made up out of a mix of LEDs, clear incandescent light bulbs, orange colored light bulbs, light bars,... This gives many controls a different color and intensity of illumination. I guess every E31 owner has noticed the HVAC control unit and center vents roller wheels are barely illuminated, but if you look closer you'll notice many other controls aren't perfect either. My goal is to make all controls light up in exactly the same intensity and BMW orange color.
The inside of the enclosure shows a part of the light bar. The light bar continues (interrupted) in the buttons.
Because I don't want to make modifications I cannot undo without damage and because the space below the buttons is occupied by the switches and spring mechanisms, I decided to reuse the light bar - but with improvements. The first change is to get rid of the light bulbs and replace those with LEDs in correct BMW orange. This will ensure illumination in the correct color.
The picture above shows the LED replacement of both light bulbs. Why that many LEDs? You may think this is to match the brightness of the light bulbs, but that's not the issue. There are LEDs that can easily outperform the intensity of the light bulbs. The problem is in the construction of the light bar and a shortcoming of LEDs. The light bar is placed very close to the bulbs. Incandescent light bulbs have a nearly 360° viewing angle, but LEDs have a rather limited viewing angle. The used Avago Technologies HSML-A101-S00J1 LEDs feature a 120° viewing angle. That's a lot for a LED, but proved to be way too less for this application. With only one LED on each side the button illumination was even worse than with the light bulbs. Not exactly an improvement thus... By putting two LEDs next to each other the length is almost equal to that of the light bulb. By adding another two LEDs angled to the construction, the viewing angle increases a lot and can match this of the original light bulb.
Now all buttons are illuminated in correct BMW orange, but the brightness of the outer buttons is still different from the inner buttons due to imperfections in the light bars. I adjusted the current through the LEDs until the weakest button was equally bright as my reference (I use the seat heating switch as reference for all my illumination mods). The current-limiting resistor is 560 ohm for this current. Obviously the other buttons are now way too bright. Each button cap contains a small light bar but the light is not evenly distributed. To fix this I had to disassemble the buttons.
I used the same approach as in the OBC button illumination mod to adjust the brightness: Small pieces of foil darken the light bar where necessary. This is a very time consuming process. Apply foil, reassemble button, put button back into enclosure, put internals with LED lighting in the enclosure, apply power and judge the result. Not good? Disassemble the whole thing again and repeat... Over and over again... Finally all buttons were equally bright. The result (together with the power sun shades button as reference - that one was modified a long time ago):
Quite nice I'd say. But I wasn't ready yet - I wanted to tackle another issue with the power window controls. Thanks to the 8 Series B-pillar-less design it's nice to drive around in the summer with all windows down. But to roll down all windows you have to press the four down buttons. Even worse is getting the windows up again because the rear windows don't roll up automatically. You have to keep the up buttons pressed until the windows are closed. According to BMW this behavior is for safety. That way the rear windows cannot roll up unattended in case someone in the back seats has something hanging outside. In my book that's just tough luck... Wouldn't it be nice to have all windows roll down or up with a single press? But I wasn't the first thinking about this. Martin, one of the founding members of this site developed a circuit that deals with this problem: the Window Control Module (FSM). Why reinvent the wheel, so I went with Martin's module.
The power window control unit transmits button presses to the A1 General Module (GM) over a serial databus. The FSM module intercepts and recodes the communication. The windows operate as normal, but when the central locking button is pressed the module enters the comfort mode for 5 seconds. During these 5 seconds any button press up or down makes all windows roll up or down automatically. Very nice... The central locking can still be activated by holding the central locking button for about a second.
Martin's FSM module is mounted on the rear of the PCB of the power window controls and fits inside the enclosure.
This concludes the modification of the power window control unit. Once again it's only a minor modification to the car, but the FSM module will make operating the windows a lot more fun and the fixed illumination brings the E31 interior illumination one step closer to perfection...
