Morning, I need to add a 115/230V AC voltage sensor, and I can not do the voltage calculation. Could someone help me?
Hi,
It is dangerous to measure the mains voltage.
You need the exact value of mains voltage?ĀØ
Are you using Arduino or Raspberry Pi?
Hi,
I would like to measure the exact voltage if it is 115 or 230V. Iām using the Arduino Mega 2560
What project are you doing?
If itās not a secret 
.
I am from SBT Santa Catarina, we have several shelters with equipment and we are mounting a monitoring system, which monitors AC and DC voltage, security camera, DHT22 sensor. It is a project, but if we succeed we will implement in 20 shelters that we have.
If I understand this correctly, you need to measure the voltage 0-115V, 0-230V or when the voltage of 115V send e-mail, or when the voltage of 230V send an e-mail.
exactly 
Iāll look into it and write to you tomorrow.
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Thank you very much, Iām waiting 
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Hallo there I am doing a Solar project to make a health center in Haiti for a charity. I want to use raspberry pi 3 with ASC712 current sensor. Please tell me how I can achieve this.
I use a board found on ebay. They call it a phase sensor but has nothing to do with phase. It accepts 100-220v and drops the voltage to usable levels. One side is powered by 5v and has an analog output. Only drawback is you have to write code to use median reads or averaging to get steady readings. See @kreggly for his thread on the code for this. Ebay item 253213012116
Good luck
Thanks allot for your answer but I canāt find @kreggy thread can you please share the link or complete name of his thread. I will be very thankful for your cooperation
What sensor were you planning on using?
The issue with using the RasPi is that it has no analog inputs, so finding an AC voltage sensor with integrated ADC would be best and then you just interface it to one of the serial buses.
One option is to take an AC to DC transformer and remove any internal regulator then use something like an ADS1115 interfaced to the I2C bus on the RasPi. The DC output voltage would be proportional to the AC input and you could reduce it down to work within the max range of the ADC with a simple resistor divider.
@wmontg5988 I believe was talking about the SCT013 current sensor which could be interfaced in a similar way to measure the current draw.
As @tad.dvor mentioned, measuring line voltage is dangerous and not recommended unless you are experienced with electrical equipment. I certainly wouldnāt recommend any solution where you are not isolated from the mains like a lot of the AC to USB power adapters. A transformer is good as it isolates, and you probably have one already in the junk box you could crack open and bypass the regulator after the bridge rectifier. Then RTV it all back together so itās pretty and safe.
Cheers,
Craig
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@saeedahmed465 I missed the part about it being a ācurrentā sensor is this your board?
https://www.ebay.com/itm/5A-Range-ACS712ELC-05B-Chip-Current-Sensor-ACS712-Module-for-Arduino/192422276337?hash=item2ccd42ecf1:g:dQcAAOSwiCRUgYha
@kreggly was dead on about tying that to an ads1115 just be sure to power both boards with 3.3v
@robsonmartinazzo curious what turned out for you.
sensor url: Single Phase Voltage Transformer Module AC Output Sensor for Arduino X9n9 F5h4 for sale online | eBay
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Just use a regular transformer to get the voltage down to a sensible safe level and then a resistive divider to get it down further if needed. I would also suggest that you protect the input to your Arduino with a zener diode just in case of a fault. You do not need much current to just measure voltage. So a divider of at least 10k ohm should work.
If you want to avoid using a transformer, then a straight resistive divider in the M ohm range will probably work but be extra carefull you have at least 2 zeners in parallel to give over voltage protection. Just be aware that there is a greater risk of shock if something fails with this arrangement.
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