help for measuring high voltage AC parameters using AVR

[faraday]

measuring high voltage AC parameters using AVR

Hi guys
I wanna measure voltage/frequency/used current up to 5A/ and used power of a AC 220V/50Hz line, with AVR, show these parameters on LCD and save maximum and minimum value of each parameters along 24hours to E2PROM.

first of all how can I convert 220v/50Hz to DC voltage that is usable for AVR?

 

[wkrug]

first of all how can I convert 220v/50Hz to DC voltage that is usable for AVR?

There are many ways to do that.
One possible is to use an True RMS to DC Converter like the AD636J.

Or to Read In the Actual Voltage very Fast with the internal A/D Converter and to Calculate the RMS Value and the Harmonics via FFT.

Do you need the Phase shift between Voltage an Current too, to calculate the effective and the blind Power?.

 

[faraday]

AD636 works for small signals, am I right? I can use voltage divider to transform 220v to very small voltage for IC, but is it reduce the resolution of measuring?

Do you need the Phase shift between Voltage an Current too, to calculate the effective and the blind Power?.

I just want reactive power.

here is a design for doing this, is it correct?
Vin=310v (220vrms)
vout=3v p-p
I sample vout each 1msec for 50msec and find maximum of voltage
[Vmax-2.5v(Vbias)]*151=Vin

 

[wkrug]

AD636 works for small signals, am I right?

Yes you are right. But I have known that Chip. You can look for something similar.

I would try to isolate the Live Part from the Measure part. You can do this with an DC/DC Converter to supply circuots at the Live Side, or use an Isolated Amplifier.
You also can use a Transformer and measure at the Low Voltage side. But that thing will make a Phase shift.

To Measure the Current I'll suggest you to use a Hall Effect IC. Allegro has some of this Parts in it's Portfolio ( www.allegromicro.com ) or LEM ( www.lem.com ). The frequency can be taken from the Voltage measure circuit, because Voltage is most time present.