BMW Auto Gamma Control

**CBDZ** · 10-04-2006, 12:24 AM

The BMW E46 (2000-2005 3 series) has a light level sensor that adjust the brightness of the LCD displays of the Stock head unit, and trip computer.

I am making a huge assumption that the signal that controls these levels is send over the I-bus. If this is the case, I would think that it would be possible to capture the signal that is sent to the displays, and use this to control the gamma levels in RR.

Does anybody now if the auto-dim is an I-bus signal?

If so, how could we use this signal to adjust the disply in RR?

I don't have any of the hardware that is needed to do any of this testing, as I am still in the planning stages of my install. I am trying to think of all the things that I would like to incorporate.

**grave** · 10-04-2006, 01:58 AM

I think it's only when you open lights: reduce HU brightness and no ibus signal.

**Jarrod** · 10-04-2006, 03:35 AM

I plan on doing the same thing with a Phidget light sensor and some crafty GammaControl programming.

**CBDZ** · 10-04-2006, 01:17 PM

Grave-

If you look at the light switch, there is a tiny white dot. Cover that dot with your finger, you will see that the display on the stock HU goes very dim, along with the display in the guage cluster. If you take a flash light and shine right on the white dot the display will get very bright.

From the liminted knowledge that I have about the system, lights are control using I-bus, along with the radio, windows, and a few other things.

**grave** · 10-04-2006, 05:30 PM

Originally Posted by CBDZ

Grave-

If you look at the light switch, there is a tiny white dot.

have you a picture of this white dot ?

Thanks.

**CBDZ** · 10-04-2006, 10:40 PM

Here are the pictures from the light control module of my 2000 323i

The First picture is the best that I could get, and the second is the same picture with an arrow pointing to the sensor.