I am trying to build a project that is able to measure the voltage/current in a electrical appliance then send a signal to the micro controller to decide whether or not to cut the power supply of the electrical appliance.

However , I am struck at the part of measuring the voltage/current using PIC[micro controller].

Please help me by showing me how.

Thanks

 

You can look over some links - http://www.edcheung.com/automa/power.htm

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2130

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2889

Please note that line voltage is lethal, so use extreme caution if you decide to pursue this idea. Have a means of determining that power is present at an output or on a wire before you touch it. Know which house breaker to open to ensure the line is deenergized.

 

its simple just make the input to the microcontroller, then convert it from analog to digital using the MIC, then compare it with values stored on registers.

lets say your converted value is 30 and your lower minumum is 25 and max value is 35 then if it is above 35 or 25 then the output of the controller should either turn on/ off your appliance.

 

Judging by your post, I'm guessing you don't have a lot of experience with electronics.

I strongly recommend not touching main's voltage for now. Just play with low DC voltages until you are a lot more experienced.

At low DC voltages if you screw up you will just get a spark, some smoke, and burnt components. At 120V you can easily end up dead.

Sure, high voltage is exciting. Dead people aren't, though. They don't move much.

 

You can measure current in perfect safety with a current transformer. Just run the high-voltage wire through the middle of a toroid with a pickup coil for the output. But I don't think you can measure voltage without connecting to the wire. Could it work via capacitance if you ran insulated wires through metal tubes, and if you then monitored the relative voltage between the tubes via a high-impedance amplifier? Could be interesting to try.