Gas gauge calibration unit

Here is an updated schematic. I moved a couple pins around for future flexibility, in controlling the LED. The LM7805 regulator could be replaced my a switch mode regulator set at 5V like Pawned used if one desires, other wise the LM7805 will need a heat sink. It is also used to power the micro, so the voltage should not exceed 5V. The gauge will still drive higher if necessary, since there is no series resistance (10 Ohm minimum sender) in the circuit.