greetings all

is there anyway to differentiate between the 220v mains and the 220v provided by an inverter (modified sine wave type) using a microcontroller or any other circuit which can be connected to a controller later. i want to switch a relay when the inverter is providing power instead of mains

 

I guess it can be done. By say looking for high frequency content. Also if you have a scope. Try looking at and compare the output then using a small 50/60 transformer. Just thinking out loud here.

 

I was hoping for some way easier.

 

Just look for zero crossings, where the signal goes a bit above zero and a bit below zero.
Two comparators tripping on something like when the signal goes above a few volts (5 or 10). This will prevent false tripping.

Make these separate comparators and compare the time between the signal going to zero (comparator one) and going from zero to negative (comparator 2), and you can do the reverse just to be sure.

With a sine wave these times will be close to zero.

With a modified sine wave these times will be much larger.

Or you could do it with an A2D converter by taking a bunch of samples and doing about the same.

 

greetings all

is there anyway to differentiate between the 220v mains and the 220v provided by an inverter (modified sine wave type) using a microcontroller or any other circuit which can be connected to a controller later. i want to switch a relay when the inverter is providing power instead of mains

You could measure inverter input (DC) or output (AC) current or tap into the control signal to the static switch.

 

Just look for zero crossings, where the signal goes a bit above zero and a bit below zero.
Two comparators tripping on something like when the signal goes above a few volts (5 or 10). This will prevent false tripping.

Make these separate comparators and compare the time between the signal going to zero (comparator one) and going from zero to negative (comparator 2), and you can do the reverse just to be sure.

With a sine wave these times will be close to zero.

With a modified sine wave these times will be much larger.

Or you could do it with an A2D converter by taking a bunch of samples and doing about the same.

I have decided to take the microcontroller route and i have managed to get zero crossing detection working using atmega8, now how should i measure the duration from the zero crossing to say 4v positive?

 

I have decided to take the microcontroller route and i have managed to get zero crossing detection working using atmega8, now how should i measure the duration from the zero crossing to say 4v positive?

Google "window comparator."

 

Google "window comparator."

But a window comparator is used to check if a voltage is within a specific voltage window, how can it be used to measure the duration?

 

Correct, you need a standard "comparator" or "zero-cross detector" as ErnieM said earlier.

 

Use a tuned filter @ 150 / 180 Hz to detect the 3rd harmonic. The Inverter output will have a much higher value.

Ramesh