> -----Original Message-----
> From: Jinx [SMTP:joecolquitt@CLEAR.NET.NZ]
> Sent: Thursday, January 04, 2001 10:31 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [EE] Phase control dimming on a cheap pic
>
> > You could just use a series cap for (relatively) lossless current
> limiting.
> > Hmm..a quick bash on my calculator says you'll need something in the
> > region of a 33 uF cap.  That's gonna be pretty large (and pricey) for a
> > 230v mains rated device.  Maybe not.
> >
> > Mike
>
> You sure about the 33uF ? If 1uF can pass 70mA then wouldn't 4u7 be
> enough for 60W ?
>
>
        Hmmm..880 ohms for a 60 watt lamp @ 230 volts.  For 10% less current
you would need 968 ohms total impedance.

        (968 * 968) - (880 * 880) all square rooted gives Xc=403 ohms.
1/(2pi*50*403) = 7.9 uF.

        OK, so my quick estimate was a little out....oops.  I should really
stop trying to do this electricity thing, university was such a long time
ago :o)

        Cheers

        Mike

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