Series Resistance-Capacitance Circuit

I have an optocoupler and I connect it to 230V, the datasheet tell me the optocoupler has a forward voltage: IF = ± 5 mA VF - 1.5 V, so, for limiting the current I need an resistor of 4.7K - 11wats, but I don't have this type of resistor so I use a Capacitor and a Resistor in series, but my problem is that I don't know how to calculate the value of the capacitor resistance (Xc=?), and if i know the capacitor value, what value resistor should have?

• – user253751 Nov 29 '19 at 13:16

The reactance of the capacitor $$\C\$$ is (magnitude): $$X_c = \frac{1} {Cw}$$ Where $$\w = 2\pi f_{Line} \$$
Net series impedance is therefore: $$|Z|= \sqrt{R^2+X_c^2}$$