SFH6186 - can someone explain me

Well the fact its an optocoupler/ isolator, then I guess you are corect. To know what its doing in a circuit we would need a circuit diagram or more info on the circuit.
Adam

 

What is written on it ? EL817 or PC817 ? Then they are opto couplers.

 

http://www.datasheetcatalog.com/datasheets_pdf/S/F/H/6/SFH6186.shtml

They are optocouplers from Vishay and Infenion. There might be other manufacturers also. There will be one resistor at the input side of the optocoupler to drop the voltage from MSP430 so that the IR diode inside the optocoupler gets the required forward voltage and it also limits the forward current of the diode inside the optocoupler. The output side will have a collector resistor and one pin of output side will be grounded and another pin which has resistor will be connected to base of another transistor which drives relay. Or it might be used as an ZCD (Zero cross detector) for a TRIAC dimmer circuit. You will get better answer if you post the circuit or PCB layout.

 

Post the image of the other side of the PCB. I guess the blue big component is a MOV. I also guess that there is a microcontroller and may be an internal or external RTC because I see a 32.768KHz quartz crystal.

What is that white 6 pin device ? Is it MOC3021 ? The part number is not clear. Post a high resolution image of both sides of the PCB.

I can see 4 resistors but there are also 4 more components pads next to it but the components are at back side of PCB. Are they diodes ?

The white 6 pin component is a fairchiald component. Post hi res image. maybe it is a OptoTriac.

What does the circuit do ?

 

Digital Utility Meter ? Hmm What does it do ? How is it powered ? What input(s) it take and what output it gives ?

 

Is it a Energy meter which shows how much power you consumed per month ? We call it energy meters here. We haven't heard something like Utility meter.

 

Maybe it is used for ZCD or I have seen energy (KWh) meters which gives pulse output which can be counted and converted to units of power consumed. You have to check which pin (pin no.) of optoisolator is connected to MSP430 MCU. I want to know whether opto's input circuit connects to MSP430 or opto's output connects to MSP430 to guess the working of the opto.

Edit

As I said there are energy meters which take pulse input and convert this to power consumed. My be opto is used for that purpose to feed pulses to MSP430.

May be it is used as ZCD to detect Voltage and Current ZC and then start a ADC conversion to detect peak voltage and current and calculate AC mains power.

Maybe it is used as a ZCD to detect ZC of AC mains voltage and current and then calculate the angle difference between voltage and current and then calculate power factor if there are no harmonics triggering the ZCD.

There might be other possibilities also.