How to measure mains voltage with mcu?!?!?

[mrcube_ns]

ac mains voltage measurement

Hi all,

I need some sugestions about measuring mains voltage 220V AC, with mcu (e.g. PIC16f870 with 10 bit A/D or similar).

I have to make mains voltage corrector (with transformer which has one primary winding and 3-4 secondary windings) with MCU (mcu must read mains voltage, and swith relays (secondary windings) to get mains voltage close to 220VAC).
So any idea, suggestion, link or comment are very welcome.

Thanks in advance.


Mr.Cube

 

[manu]

avr mains voltage measurement

Two resistors in series? Take care of their breakbown voltage, most of resistors are rated for 200v maximum.

 

[mrcube_ns]

avr measure ac

hi manu,

You mean to make simple voltage divider with 2 resistors?

Mr.Cube

 

[daviddlc]

pcb design mains voltage isolation

Check out the shunt resistors, this can be a possibility as well.

 

[mrcube_ns]

measure mains voltage

hi daviddlc,

Shunt resistors have very small resistance and usually can have great current.

One of problems with resistor solution is that all pcb will be on mains voltage, which I want to avoid.

Some isolation is neccessery, and with isolation some voltage level transformer.

I have idea to use transformer 220VAC/12VAC (or similar) and do everithing with isolated small voltage.

BUT,

with transformer I still have problem how to measure AC voltage with mcu precise (as can be)???

Some schematics (or text description) or idea how to do it will help.

Thanks!

Mr.Cube

 

[madicalphy]

schema voltmetr mcu

schematics is needed to understand.

 

[darla1]

measuring mains voltage harmonics

hi

see the schematics and use all four resistors as 580k for 230v ac mains, in my schematics those are diffarent, iused it for 440vac......

darla

 

[Faizan Jawaid]

ac voltage mcu

220VAC has a peak of 320 volts...becoz voltmeter shows us Vrms values...make a simple voltage divided that gives max output of 5 volts max at 320v input...

 

[yhw19]

how to measure mains voltage

hi darla,

is that an amplifer?

Added after 24 seconds:

in your schematic i mean