how to measure ac 230v as it is varying with time and it is quite a high voltage . Also the current .Do i have to use an external analog to digital converter?
Both topics are covered here: How to build an arduino energy monitor | Archived Forum
Is there another way to measure current?
There are 2 other methods to measure current.
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Use a small resistance e.f. 1/100 or 1/100 ohm resistor and measure the voltage across the resistor
The drawback with this method, is that the whole circuit needs to be connected to the mains Live wire.
There is a circuit for this see GitHub - lukeweston/SEGPlug however I tried to build it, and it didnt work for me as there appeared to be too much noise to get a decent current reading
But it was impossible for me to debug what was going wrong, as the whole arduino had to be in a electrically sealed box and I had to send the serial data via a radio link to monitor what was happening. -
Use a hall effect device / IC e
e,g, http://www.ebay.com/itm/5A-range-ACS712-module-current-sensor-module-/250897213267?pt=LH_DefaultDomain_0&hash=item3a6aa3a753
These come in various current ratings, you'd need to find one that matched your requirement -
There are custom power monitoring IC's that read both voltage an current (via the method outlined in (1) above) but they suffer from the same issues as outlined in (1), i.e they operated connected directly to the mains, so you have to have opto isolated comminication with them via SPI.
An example of this sort of IC is Cirrus Logic, Inc. | Cirrus Logic
again, I have some of these, but decided it was too hard to use them
Hence I'm currently using the current clamp method as used by the OpenEnergy Monitor project.
However I also have the Hall effect devices that I linked to, and I may get around to using them in the future, but they are not as safe to use as the a current clamp.