Ever since man learned about light, the perception has been ‘more light is better.’ More light, more light, more light! But what we have found lately is that the correct amount of light with the correct spectral content of light is better light.”
So says Mahendra Dassanayake, technical leader and lighting specialist with the Ford Motor Company. According to Dassanayake, the concept of “quality of light” is relatively new to the automotive lighting field, but it’s becoming a bigger issue every day.
“It’s just like sound,” he explains. “You have sound with medium, low and high-band frequencies, or you can have a certain amount of compressed sound. And when you do that it’s the perception that you need to address: you tune the visual perception based on how I see light in a more meaningful light—not just spilling a lot of light and saying you have good visibility.
“There’s a lot coming up with light sources and using LED (light-emitting diode) light,” he says, “so it’s a broad brush discussion if you say ‘LED light.’ At the lowest common denominator, it is a diode, but how do you use that light out of the diode in a more energy-efficient, smarter, more intelligent way? There are 1,500 ways of going at it.”
SMARTER, NOT BRIGHTER
The good news is that fleet maintenance managers don’t have to deal with 1,500 different approaches to vehicle lighting—yet. But the days of the simple plug-in, electric-filament halogen bulb are fading fast as LED and HID (high-intensity discharge) lighting technologies migrate from Cadillac and Lexus models to lower-priced, fleet-appropriate vehicles.
“We are moving towards different light sources for lamps,” says Michael Larsen, bill of material family expert—in other words, a lighting expert—at General Motors.
“The LED is the new light source that’s out there,” Larsen says. “You see it in a lot of signal lamps. I know the heavy-duty industry has really adapted to these requirements where, depending on the state, if a bulb burns out, you can’t drive the vehicle. You have to fix the bulb. So, the trucking companies have figured out that if they spend the extra money on these LEDs then they don’t have to worry about whether a driver’s going to be stuck somewhere for an hour or two while he’s trying to get some stupid 10-cent bulb while he’s trying to get his truck on the road!”
Larsen says that automakers are using more LED lighting for the same reason, but that light-duty vehicles also benefit from the longer life, lower power consumption, and, yes, enhanced styling opportunities afforded by LEDs.
Surprisingly, LED lighting also promises what Larsen describes as a “fairly significant” improvement in fuel efficiency, simply because it draws so little power.
“LEDs are such low-power consumption,” he says. “Take a stop lamp: If you use a standard bulb, you’re probably at 21 watts, and if you do it in LED you’re at five watts. Most of the LED lamps on a vehicle, you can easily run them on a 9V battery. In a standard stop lamp, you would use a 150 milliamp LED, so if you use 10 of them that’s one and a half amps at four volts.”
According to Jayson Ryan, senior manager, OEM sales & product marketing for Philips Automotive Lighting North America, the watts used by headlights are directly proportional to fuel consumption.
“Typically if you look at a halogen bulb, it uses 55 to 60 watts per side. When you implement HID technology, HID runs at about 35 watts per side. So you can immediately see a dramatic improvement in power consumption from your lamps, which is directly translated into mileage. You don’t have to spec’ out as big an alternator, which affects weight, which will improve gas mileage.”
SAFE AND SOUND
There are other good reasons to consider switching from incandescent vehicle lighting, chief among them safety. We’ve already touched on the “quality of light” issue; as Dassanayake says, “...the correct amount of light with the correct spectral content of light is better light.”
Lessons in LED