Gabriel Callao 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 ?
>
I would consider rectifying the 220v AC to DC and then switching in a
matrix using IGBTs.
The High Side switches would be N channel as would the Low Side
switches. The High Side gate drive will float and obtain their power
from small high frequency transformers, the gates being triggered by
opto couplers.
Thats 12 IGBTs and driver ccts.

I am presently in the final design stages of a variable freq 230vac
source and this is the technique I have chosen.

Note that the supply to the lamps will at best be muxed at 5:1 so
brightness may be a problem.

There are some seriously dangerous voltages and high insantaneous
currents present so beware. (Standard warning for newbies who might
not fully understand the dangers involved). Kids... dont try this at
home.
_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

www.psych.auckland.ac.nz

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