can anyone help me to give me a program arduino acs712-20a to measure 220Vac, i very confuse to make it this program 
this is my first program
sensor_arus__1_.ino (530 Bytes)
The 20A version is 100mV/A.
The middle is 2.5V and dividing it by 0.100 makes it amperes. Your calculation is okay.
Is your ACS712 module designed to work with 220V ? Most of them are not.
The ACS712 is in most cases dangerous to use with 220V, you better use a Current Transformer.
You take one sample every second, but the 220V is alternating at 50 or 60Hz. To know the current, you have to measure the current at a much higher rate and calculate the current.
Have a look at the openenergymonitor, there is a lot of useful information : http://openenergymonitor.org/emon/buildingblocks/ct-sensors-interface
Bingung nya Sebelah Mana nya gan ?
You can use this github library to measure 220V AC current:
Peter_n:
Is your ACS712 module designed to work with 220V ? Most of them are not.
The ACS712 is in most cases dangerous to use with 220V, you better use a Current Transformer.
The ACS712 says its double-insulated rating is 130Vac (184 peak). But the single-insulated
rating is 250Vac. So if its used with a low-voltage side connected to PE (protective earth),
it is OK, I think - anyone confirm that analysis?