Hello,

I'm new here. I am designing a simple circuit to run 6 LEDs off AC current (110 - 120V, 60hz). The LEDs have a Vf of 3.3 and 30ma. I want to use a capacitor to limit the voltage to the LEDS. How do I calculate the size of capacitor I need? I have seen the formula C=1/(2*pi*f*X). Is X the resistance needed in the circuit? So I just find out what resistance I need using R=V/I, plug that in for X, and solve for C?

Thanks for the help.

 

Hello,

Using leds directly on the mains can be unsafe.
The mains power can be leathal.

Greetings,
Bertus

 

I am actually going to use them in a lamp.

 

Use a step down transformer. No circuit running off the line can be made safe - it always presents a lethal shock hazard.

 

Ok, I'll look into a transformer. Thanks for the info.

However just for my knowledge, is the formula I asked about in my first post correct?

 

Hello,

Yes. Take a look at this page from the AAC eBook for more info:
http://www.allaboutcircuits.com/vol_2/chpt_4/2.html

Greetings,
Bertus