On Thu, 11 Nov 1999 10:18:53 -0300, you wrote:

>Hi all,
>
>    I have to make a 220volt lamp matrix of 7x5 lamps=35 lamps. With it, I
>will be able to "draw" different letters. If they were leds, I would only
>need to control a row (or a column) and do refreshment in every other column
>(or row).
>    Does anyone know how to control all these lamps using the fewer lines of
>a Pic micro, and also fewer triacs ?
>
>
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Assuming they aren't very big lamps, you may be able to use
opto-triacs like the very cheap MOC3020 to drive each lamp.
 You could wire all the LEDs of the MOC3020's in a 5x7 matrix, and
send a firing pulse to those required to be on early every  mains
half-cycle. You could drive them directly from 12 PIC pins. You could
get this down to 8 pins if you used a HC138 as a row decoder.
You could even do selective dimming with this arrangement - fading-in
the lamps would make them last significantly longer.