Low-power backlighting

Electroluminescent backlighting is making inroads into instrument clusters. Electroluminescent (EL) backlighting has an allure that continues to attract designers in the automotive industry. Its thin, uniform lighting properties let EL keep instrument cluster design time to a minimum. The resulting dashes are also comparably simple. EL lamps create uniform lighting for both silhouette and traditional instrument clusters though they are less than 0.25-mm thick (about half the diameter of the lead in a typical mechanical pencil). They are flexible enough to fit into a medley of configurations and need no light pipes or compensated graphics. They also don't generate much heat and won't burn out. The retrofitting of EL into an instrument cluster requires no major changes to other components. But there are important benefits, such as size and weight reduction if the cluster is designed around EL technology. EL lamps frequently mount between a subdial (backplate) and a graphic overlay (appliqué). The subdial can be inexpensive black ABS. The subdial, EL lamp, graphics appliqué, and EL driver electronics (EL inverter) can be a single unit that snaps into the instrument cluster. This provides one plug-in subassembly that completely illuminates the dial. Stepper motors that move the pointers can also mount on the subdial. If there's no requirement for a complete lighting subassembly, then EL and graphics-appliqué components can mount on the instrument cluster via alignment holes or slots. The EL lamp and appliqué stay in place with a bezel and lens which snap or screw on top. Typical mounting options include affixing the lamp and appliqué at the center hole of each gage via ultrasonic welding or orbital forming. The lamp and appliqué edges are held flat against the instrument cluster by either snap fitting or adhesively bonding the faceplate to the assembly. EL lamps need an ac drive signal,