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?
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?
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
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.