Measuring Voltage from the Mains

[Fiann]

My project is to build a digital watt meter, to measure the Voltage, Current, Power, etc. from an appliance connected.

My question is, is there a way I could measure voltage from a 240V/50Hz mains connecting to an appliance?

Please do not suggest Voltmeter, because the watt meter I'm building will be a stand-alone product.

 

[GSM Man]

There are a couple of chips availble for Power Meter front-ends.

Cirrus - https://www.cirrus.com/en/products/pro/detail/P1084.html

Microchip - https://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en520376

These links are a good place to start looking at your options.

 

[cameo_2007]

simple method.
use a step down transformer and bring the 240V to a lower level. and using resistor dividers , feed it to the adc of the microcontroller.
and for current measurement just use a CT and you have the current.
then its just substituion in the equation to know the power.

 

[mfarooq1]

Its easy,
Use transformer for best isolation and conversion of voltages to low rang and use ADC to measure your voltage.
but you need to make a lookup table for translating ADC values to voltages scaled from 240 to 5-10 volts by transformer.

 

[garg29]

Not that easy without those specific ICs. cameo_2007 you are a advance member how can you suggest this type of incomplete solution. Fiann says "the watt meter I'm building will be a stand-alone product" He will have to measure p.f. (power factor) also to know wattage.