Resistor choice for an optotriac

Hi,

I recently found this schematic :

However I don't understand why they put the R2 resistor; it will create a loop with the 230V and a high current will pass in the R2 and R3 resistors. Without it, there is just a 10-20mA current, but with it, I calculated I=(U-Vopto)/(R2+R3)=approx 200A :S

I think I am wrong but I don't know where...

Thank you.

That’s for the zero-crossing
Refer to page 7 of the Fairchild datasheet, Fig. 10

Hi, IF the Optotriac turned on and the big external TRIAC did NOT, or was missing, then the full line voltage would appear across those resistors and there would be Instant Smoke.

But because electronics is Almost Perfect that Almost Never happens...

Oh great! I hope I will be lucky^^
If it is just a switch, is the resistor really important?

[quote author=Cow faith link=topic=107545.msg807890#msg807890 date=1338150704] Oh great! I hope I will be lucky^^ If it is just a switch, is the resistor really important? [/quote]

There are no optional components shown except the 39? and 0u01 (constituting a "snubber network") in Fig 10 which are only needed for use with inductive loads.

Ok thank you!!