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Abstract
Various studies to identify the factors that affect the life of incandescent light bulbs in motor vehicles have been conducted by many different companies over, many, many years.
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Effect of Filament Coil Location on Incandescent Bulb Life
Various studies to identify the factors that affect the life of incandescent light bulbs in motor vehicles have been conducted by many different companies over many, many years.
A designed experiment (DOE) was conducted utilizing a fixture containing numerous motor vehicle signal lamp incandescent bulbs mounted to a vibration table. The vibration table was run at vibration levels determined by real world measurements made from accelerometers mounted directly on the tail lamp bulb in- vehicle and on-road. In addition, the bulbs in the DOE test were cycled on-and-off per a duty cycle that mimicked results obtained from real world in-vehicle tail lamp bulb usage measurements.
The picture above shows an incandescent dual-filament vehicle tail lamp bulb (type 3157K). The bulb's major filament is of primary concern for bulb life. The major filament, a higher wattage than the minor filament located just above the major filament, performs the stop (brake) and turn functions.
Bulb life data was monitored for the bulbs in the DOE test, and subsequent statistical analysis showed that the location of the major filament coil was a key factor that affected bulb life. Specifically, bulbs in the test with their filament coil centered between the lead wires lasted much longer than bulbs with their major filament coil offset towards either of the lead wires. The plots below, based on the DOE test results, show the predicte...
