Are you wonder how much it will cost you to leave your television in standby mode whole night, did you know how much change your refrigerator settings will make on your electric bill.
This is an AC WATT Meter wich can measure the real power consumption, of a device connected to the 230Vrms /50Hz mains line .The PIC microcontroller collects the voltage and the current information with the help ofADCs and then calculates the RMS voltage of the mains line ,RMS current drawn by the device and the resulting avarage power consumption.
To calculate the power ,we need to know the voltage across the load and the current drawn by the load ,the voltage that should be measured is directly the mains voltage.
We know that the voltage is 230Vrms /50Hz but it has a 10 % tolerence .So the voltage can change between 207Vrms and 253 Vrms.To make an accurate power measurment it will be better to measure the mains voltage instead of putting 230Vrms into the calculations.
The microcontroller of the wattmeter is PIC18F252,basically it reads the voltage and the current and calculates the RMS voltage ,the RMS current and the average power.
Designing the wattmeter as a handheld device was a good idea,the outline of the PCB was drawn accordinaly ,autocad was used to draw the outline and the .dxf file was umported in SoloPCB.