Ac 220v input and filtered output

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imranahmed

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Please let me know I make this attached circuit for ATmega8 based voltmeter but reading is displaying

only first one rest of the two digits are not standing they are up/down fast.And if input DC voltage

the voltmeter shows good display.
 

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Try increasing the value of C2 to 1000uF.
If it doesn't work, then using a bridge rectifier at the input should help!
 

In my view you need probably averaging method first of all you are converting the AC in to half cycle DC and then trying to sample it at different point of time will give you different voltages ..... Capacitor my filter it out up to some extend but reading will not be reliable as the discharging of capacitor will happen through 10k and POT resistor that you put...... As rachit suggested you can put higher value of capacitor but that still be empirical and capacitor may or may not discharge full in the blocked negative cycle..... of course it depend on the you application why you need down sampled voltage and it's what should be it's range.... the traditional voltmeters generally do the averaging....

Good Luck
 

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