Eben

No. It is wrong.
The 1k Resistor is a current limitator.
The equation you must use is P =3D R.(i^2). Consequence of P=3Di.U and =
U=3DR.i
"R" is easy: 1k
"i" is almos equal the Triac Gate current. It depends of the Triac you =
choose.
    You must see in it's DataSheet. Generaly it is very low.
I am not shure, but I guess that a 1/4W will work ok.

Augusto de Conto
augusto@automacao.eng.br

  ----- Original Message -----=20
  From: Eben Olson=20
  To: PICLIST@MITVMA.MIT.EDU=20
  Sent: Friday, December 14, 2001 10:24 PM
  Subject: [EE] question about light dimmer circuit


  Hi all. I'm trying to build some PIC-controlled light dimmers for my =
school theater. After looking at some schematics from the internet, I =
pieced together the attached basic diagram. But if anyone has experience =
with this kind of thing, I have a few questions. I'm very confused about =
how to calculate the wattages required for the resistors. Using V=3DIR, =
and P=3DVI, it seems like the 1k resistor between AC supply and the MOC =
triac trigger would have to take about 15 watts. Is this correct?
  TIA,
      Eben Olson

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