Interior Lighting Control

Basic Description

Years ago, the interior lighting in cars consisted of a few incandescent lights that turned on or off in response to microswitches in various doors or simple switches near the light fixture. Today's cars may have more than a dozen interior lights (mostly LEDs) whose function and brightness are computer controlled. Interior lights are typically located in the ceiling (the dome light), the doors, the console, the dash, the trunk, above or between the visors, and various other places within the vehicle. These lights provide illumination for the driver and passengers to enter and exit the vehicle; they illuminate certain control surfaces; and they add style and warmth to vehicle interiors. The electronic control unit that activates the lights, uses information from door lock position sensors, various door position sensors, the ignition switch, ambient light sensors and occupant-adjustable switches and potentiometers to determine the appropriate illumination levels for each light. Interior lighting levels may be controlled by a vehicle's body control module; or the control of various lights may be handled by different processors distributed throughout the vehicle.

Lighting control modules control the brightness of individual lights using pulse-width modulated (PWM) signals that typically turn the light on and off at a frequency of about 200 kHz. Once the lights are activated, they may remain powered on for a certain amount of time and then dim until powered off.

LEDs (light emitting diodes) have largely replaced incandescent lights for interior lighting applications due to their higher efficiency and longer life.

Some recent interior lighting innovations include systems that adjust the color and brightness of various lights in response to the ambient temperature (for a warmer or cooler feeling) and systems that replace traditional manually operated switches with motion and/or proximity sensors.

Sensors

Switches in dash and doors, potentiometers, ambient light sensors, motion sensors, proximity sensors, temperature sensors

Actuators

Lights

Data Communications

Control Unit Communication: Typically CAN or LIN

Manufacturers

Delphi, Hella

For More Information

[1] Automotive Lighting, Wikipedia.

[2] Spotlight on Automotive Interior Lighting, Peter Murphy, Machine Design, Feb. 21, 2001.

[3] BMW X5 Interior Lighting, YouTube, Sep. 2009.

[4] Mazda 3 Interior Lighting Complete, YouTube, Dec. 2008.

[5] Interior Blue LED Lighting in Motion, YouTube, July 2008.