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Topic: Need to measure 230v 50Hz a.c. voltage using arduino (Read 3595 times) previous topic - next topic


Guys I'm trying to build a prototype energy meter. Al I need is display voltage current and power.I am able to measure the current but not the village. Plz any 1 tell me how to measure 230v a.c.


Hi there,
Not sure if you have solved your problem yet but this is what I would do.
Buy a small 230v to 6v transformer. 3VA would be ok.
The output will be around 6v RMS
You need a bridge rectifier (W 01) to convert to DC. 2 terminals AC, one + and one - out.
This will not be a smooth DC. To smooth you need a capacitior like 15uf 25v
That will give you DC but it will "store" the peak value which is 1.4 x the 6v RMS = 8.4v also too high for the board.
Get 2x 470R  1/4 w resistors in series across the capacitor. Connect the "-" end to GND. the junction of the resistors should now have about 4.2v. I would not connect that directly to an analogue input but put somethink like a 4K7 resistor in series. This should protect the input from sudden voltage spikes.

Your software needs to be able to calibrate the system.
VERY CAREFULLY measure the AC Mains voltage - may be it is 225v AC. Use the ADC in the Arduino to see what the value is on the analogue port for that voltage and work out a conversion factor.
You will need to average several readings I would suggest may be 100 readings over a couple of seconds.
Note this will give you an average reading. For voltage this is ok as the mains is a fairly good sine wave. However your current measuring device should be an RMS current detector (and must be isolated from the power) to get any sort of accuracy.


direct measurement can be done using voltage divider by 1k and 1000k resistor but it is risky (sefety of equipment as well as yourself) hence use transformer or optocouple. using transfor of 6-0 or 6-0-6,  240 or more but still you need  diode (for dc) and voltage devider (mcu pin only acceps 0v to <5v). measuring ov to 2v is faily ok.


I would suggest you to use the non- invasive current transformer which will convert AC voltage to smaller DC voltage which can then be fed to the analog input.

You might need to take a look at caliberation after installation

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