how to check live AC line?

[nisarg001]

I am creating project kind of a logger. When any AC appliance is turned on it's signal goes to microcontroller and date/time are stored in flash memory.
Right now, I am thinking of putting transformer in parallel with AC line and then converting it to dc in usual way. But it will make my circuit bulkier.

Is there any other way to say AC line is on or off for microcontroller compatible voltage? is there any sampling IC available?

Thank you!

 

[sreevyas]

Hi!

For low pwoer applications direct IC is there or you can do with diode also, i have done couple of years back, find out on the net, i could not recollect properly

_sree

 

[FvM]

Cause AC on/off is a digital information, an optocoupler would be the least expensive part available for signal isolation (assuming isolation is required at all).

 

[nisarg001]

Thanks you so much FvM. But will optocoupler work at 230V AC????

 

[max0412]

See AN521 Interfacing to AC power lines

https://ww1.microchip.com/downloads/en/AppNotes/00521c.pdf

and

TB3013 Using the ESD Parasitic Diodes on Mixed Signal Microcontrollers

https://ww1.microchip.com/downloads/en/AppNotes/93013a.pdf

 

[umery2k75]

I had seen protecting diode in the input pin. Recommendation for 5MOhm resistance was mention, I think 1/4 watt resistor would work over here. Because MCU won't be sinking >20mA of current and there's any need for 5W resistor.

 

[FvM]

will optocoupler work at 230V AC

It needs a current limiting resistor anyway, in this case, the resistor has to dimensioned for power line voltage. Also, you need at least an antiparallel diode to cut off the negative half waves, respectively an AC input optocoupler or a small bridge rectifier.

 

[antedeluvian]

Use a relay with a 230VAC coil.
-Aubrey

P.S. gold contacts are better since you will likely have very little current passing through them and the contact resistance tends to deteriorate over time.

 

[nisarg001]

Thank you all!!

 

[hakeen]

Hi,

Another interesting solution would be a special optocoupler designed for AC/DC sensing. It is really integrated solution HCPL-0370



It helps a lot.

Cheers
Hakeen