i came across the project where there is a Variac transformer which gives 36 V ac in output when it max.
it can be down by selector knob. Now i give that voltage to arduino mega adc from bridge rectifier and voltage divider circuit.
My problem is -> on same voltage of variac, arduino changes adc count more than 200 points up or down continuously. i checked with multimeter that ,there is no change in voltage divider output. grounds are also connected properly.
i checked that adc is not failed as i checked with dc power supply, and that gives stable count. please help me out
If you were to look at your rectified voltage with a scope and then look at your rectified power supply voltage I would venture the wave forms would not even be close to the same. As Mark points out your rectifier out is hardly a nice clean DC voltage. Less any filtering it will have an AC component so you want to start with some filtering, like a capacitor.