[hvalentim]

I have been doing some testing using a 80W solar panel and a 20A solar regulator which I already had lying around. Now, the thing is: the solar regulator is a 10 year old linear model which most of the time (when the Sun is shinning bright) produces a permanent voltage oscillation of around 2v (say it constantly goes from 15,6v to 13,6 volts to 15,6v to 13,6v....). This happens both in the battery charge and DC supply parts.

I am wondering if the 7809 will help handling/curbing this. Would it just mimic this oscillation in the 9v output or will it somehow attenuate the gap? What about the Arduino? Can this mangle the reference voltage (and consequently the readings)?