Drives 1-2 Luxeon LEDs at different currents from separate power inputs

This circuit is designed to replace a dual-filament incandescent bulb in a combined brake/tail light for automotive use. When power is applied to the ‘Tail’ input the current in the LED is regulated to 300mA. When power is applied to the ‘Brake’ input or both inputs simultaneously, the current in the LED increases to 900mA. The ‘Brake’ and ‘Tail’ input voltage can vary between 8V and 40V This makes the circuit suitable for standard passenger cars and trucks with 8V-16V batteries as well as freight trucks, tow trucks, fork lifts, and other vehicles that use a double lead-acid battery system, or 16V-32V.