This circuit can be used in the car to convert the 12 V from the battery in 6 or 9 V up to 2 A. The transistor must be mounted on a heatsink and the zenner determines the output voltage. The zener must have 0.6 V above the desired voltage in the output. For instance, if you want 6 V use a 6.8 V zener.
12 to 9 or 6 V Converter
