Tom, sorry to cause any confusion when I said "First pic is without a resistor from A0 to ground, fully rectifies ac" as rectifies should just say rectified circuit. I was just making reference to the fact that I started with an AC signal and rectified it before going to the Arduino. I can provide a schematic, but here... this is what I did:
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Start with 12vac
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Then goes into a voltage divider circuit which split the signal to about 10.5v on one side and 1.5v on the other.
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The 1.5v side of the divided circuit goes through a 4 diode, rectifier circuit to give me a half sine that does not cross 0v (all positive voltage now). This 0 to 1.5 volt sine goes into my A0 pin.
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I (as well) connected a 1k resistor from A0 to ground, as well as a 50uF cap from A0 to ground and now get a nice steady 1.5v (approximately). I can get an even smoother output with a larger cap, however I noticed that if I change voltages slightly (via messing around with the voltage divider), larger caps can make the output slow to change (which I don't want). 50Uf seems to be what I'm looking for.
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Have a drink, eat a pie, all is good
- I can draw out my schematic if anyone wants to see it.