Hi guys so i made a obd socket for my car that will capture some data, I ended up using an lm7805 to regulate the charging voltage of my car which will be around 14.1volts to 5volts to run atmega328AU chip. I have also soldered in protection diode with the additional capacitors aswell although i am worried it will create alot of heat due to having to drop near enough 9volts. I unfortunately do not have the space to add a heat sink so would i be ok with adding a resistor in series with the power line going into the lm7805 to roughly drop the input voltage down to 8volts? I was thinking of adding a 13ohm resistor which should if calculations are right dop the voltage down to 8volts while the vehicle is not running/charging.?
fyi (the only space i have for any heatsink would be to place it on top of the lm7805 with paste but i do not fancy doing just incase)