Calculate Capacitance

Discussion in 'General Electronics Chat' started by wkumtrider, Jun 3, 2009.

  1. wkumtrider

    Thread Starter Member

    Jun 3, 2009
    14
    0
    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.
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,641
    2,344
    Hello,

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

    Greetings,
    Bertus
     
  3. wkumtrider

    Thread Starter Member

    Jun 3, 2009
    14
    0
    I am actually going to use them in a lamp.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Use a step down transformer. No circuit running off the line can be made safe - it always presents a lethal shock hazard.
     
  5. wkumtrider

    Thread Starter Member

    Jun 3, 2009
    14
    0
    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?
     
  6. bertus

    Administrator

    Apr 5, 2008
    15,641
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