Tungsten Wire Refuses to Die in Automotive Lighting

January 7, 2016 Joshua Jablons Ph.D.

If the future of LEDs is now, why are incandescent lamps still used for automobile turn signals?

In today’s automotive systems, even relatively “simple” applications such as headlights, taillights, brake lights, and turn signals are prime targets for innovations in technology. But while people crow about the growing use of LEDs in automotive lighting, one application remains somewhat elusive: the “blinker,” which is still a stalwart of tungsten wire and the incandescent lamp.

Supplying the Tungsten Wire That Powers Turn Signal Lamps

We’ve talked before about tungsten wire and its unique properties — including high melting point, low vapor pressure, high tensile strength, and excellent corrosion resistance — that make it a material that cannot be easily replaced in certain applications across different industries. (You can read our earlier blog about tungsten wire here.) One such application is the alleged poster child of obsolescence, the incandescent lamp.

As a supplier of metal parts and materials for the automotive industry, Metal Cutting provides tungsten wire to manufacturers that use it expressly for the purpose of making automotive turn signal lamps. In addition, beyond our own experience, there is evidence to support the continued use of incandescent lamps for turn signals.

An Anecdotal Look at Incandescent vs. LED

Contrary to what LED makers say, incandescent turn signal lamps and their tungsten wire filaments are designed to last for at least 10 years or, effectively, the life of a car. Balance this against the initial and replacement costs of LEDs and the claim that they last longer than a car’s life, and incandescent lamps come out ahead — or at least pull up even. (After all, who cares if the LEDs are still working when the car is relegated to the junkyard?)

On the typical automobile, there are six locations for turn signal lamps — two on the front end, two on the back, and (in late model cars) two on the side, either integrated into the side mirrors or, as in Europe for many years, along the rear of the front fender. Yet, if tungsten wire filament lamps were so comparatively short-lived, wouldn’t we be replacing those blinkers on a near-constant basis? Compared with headlight, taillight, and brake light lamps, how often have you had to replace even one of four or six turn signal lamps?

Designed with Tungsten Wire to Cycle On and Off Effectively

Unlike what is optimal for most electronic devices, the turn signal function in automobiles must be designed to flash on and off rapidly and repeatedly; in fact, its sole purpose is to do precisely that, at a rate of 60 to 120 “blinks” per minute. So, blinker lamps require rapid on-off thermal cycling of the electronic component — something that no “digital” electronic component handles well, but incandescent lamps, with their tungsten wire filaments, do.

With digital components, meaning those made of integrated circuits, the best practice for longevity is to turn them on and leave them on. Of course, that practice might not be entirely carbon neutral or there are battery life concerns, so there is usually a “sleep” function, but the current remains flowing. It is all about thermal cycling, which is an adverse condition for electronics, and LED lamps are fundamentally a printed circuit that doesn’t like thermal cycling.

While some lamp manufacturers and carmakers are, indeed, working diligently on building a more effective blinker function into their “all-in-one” LED headlight and daytime running light (DRL) designs, it is far from ubiquitous. So, for the time being at least, tungsten wire and incandescent lamps remain a viable long-life, low-cost solution for automobile turn signals.

As these lighting technologies advance, Metal Cutting will continue to be here to meet the needs of the automotive industry. As a precision metal fabricating company, we are expert in very tight tolerance cutting, grinding, lapping, and polishing of all metals for automotive safety systems, fuel injections systems, and lighting system. We also provide secondary operations such as bending, angle cutting, and pointing and slotting of small diameter tubes, wires, and rods. In addition, tungsten and molybdenum products, such as wire, ribbon and rod, are available.

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