So, as anyone with an aftermarket head unit knows, the lighting is usually green & blue, or something horrible like that. Well, horrible in that BMW lighting is orange & the head unit stands out a lot with green buttons & such. I got tired of that, and being that my office has a pretty extensive electronics reworking lab, I decided to use some time after-hours to play around.
First, some details.- The official color specification for control panel backlighting in BMW's is 605nm orange. Knowing this makes the selection of lighting components a lot easier.
- In the case of my Pioneer DEH-P3700 head unit, the LED's used inside were of the 0603 (1208 metric) surface-mount type. Pretty common stuff, and Digi-Key had some for me at $0.045 each (in a quantity of 100).
- In the end, I opted to backlight the LCD screen with 615nm red (has a slight hint of orange to it), and the buttons with 605nm orange. I tried 605nm for the LCD initially, but it was far too much orange and didn't look right.
- None of the pictures of the thing installed in the car look quite right...the stock stuff has light passing through orange filters, and the radio unit doesn't, the light from the LED's comes right through. To the human eye, it looks just fine, but the LED's come off as too yellow on camera. So, pictures that make it look really yellow in-car are not correct...it matches perfectly in-person.
Enough talk, picture time.
The very first time through with this, I pulled off a large incandescent bulb and replaced it with a T1 sized 605nm LED. It didn't really work though (details further on). I had to make my own resistor array dealy to limit current to the LED, and had to stack a bunch in parallel as they could only handle ~0.06W each. I didn't want to let the smoke out of them...
From a little further out. These are 0603-sized resistors (1208 metric...1.2mm x 0.8mm).
Next I began swapping the SMD LED's. The trick is having 2 soldering irons. Removing the original ones requires an iron in each hand, and picking the old one up with them as you can melt both solder joints. Clean the pads with some solder wick & contact cleaner, then put a little fresh solder on ONE pad. With tweezers & one iron, place the new LED & get it positioned properly, melting it onto the one pad. Once good, add some solder to the 2nd pad.
All of them swapped & being tested.
It turned out that all of the lights were too bright (except for the big one...it only emits useful light up to 60 degrees off-ax-s, and the light diffuser in the faceplate was more like 90 degrees off axis). So, I traced out the connections on the PCB & started swapping the other current limiting resistors.
I also decided to try something else where the big LED was. According to the data sheets, the little SMD ones actually put out more light than the big one. They also have a useful viewing angle of 160 degrees, instead of just 60. This would prove to work far better with the light diffuser part. There's the advantage of incandescent bulbs right there...they are almost omni-directional.
More fun swapping resistors. Still too bright.
A quick test. Hmm, that LCD screen just isn't right.
The LCD screen was originally backlit with some non-standard white LED's. Well, some of my orange ones turned on their side would have to suffice (I broke the original ones when removing them anyway...so I HAD to make it work lol).
Much better! That's a lot of orange, though. Notice that the orange in this shot actually looks about right. In-person it looks the same.
Here's the rework station I was using. 4 Metcal irons...if only I had 4 hands. Soldering with both hands is fun stuff.
Here's one of those bad looking pictures I mentioned at the beginning. I swear, in person it looks superb. It is a white balance issue with the camera...the LED's require one setting to look right, and the others a different one. Imagine the HU, but colored as in 2 shots above. It has to do with the orange filters on the rest of the console & the lack of orange filters on the HU. You'll just have to take my word for it, it matches.
Here's a final one. I spent a good 4 hours one night messing with the resistors more. The lights were just too damn bright. The LED's I used were about 3300% more efficient than the ones I pulled off, so I had to drop the running current from ~20mA to ~0.6mA. I also put some 615nm LED's in for the backlight on the LCD screen. It helped match things up to the OBC a little better. Actually, this is probably a better one to compare the lab-shot to. The WB was poopy on the one above, and the rest of the lighting looks pink. I am putting the lab-shot below (again) for better comparison. Keep in mind, the LCD screen lights were later swapped to be more red.
(I PS'ed this one a little. This is about as close as I could get it to looking like it does in person. Still, things are too yellow in this pic...oh well.)
Speaking of the OBC...I did my 13 button OBC swap this past weekend. I also did some...over-the-top custom backlighting work on it lol. Hell, I only used 15 of the 100 LED's I ordered on the radio.......that'll be a new thread.
