AVR-Chat

Massimo,
   Thanks,
   I'm leaning towards triacs, but still have to do some tests. I was aware 
of the fact that some inverters have a square wave output that can keep the 
triacs from turning off properly, but did not think of an rc network to 
slow the down the edges enough to fix the problem. Still don't think I need 
the opto isolation, but we'll see.

    Also, I'd like to avoid the one switch per segment solution (rather use 
24 triacs then 96) , but not sure how much brightness I'll loose to the 
scanning process.   More tests.

-carl

At 08:31 PM 12/3/2004, you wrote:

>I have built quite a large installation for the venice biennale using
>100 pieces of el paper driven by 1 small microcontroller.
>
>The way i did it is by using a triac based optocoupler (MOC 32020) to
>switch every panel on and off. These were connected in groups of 20
>to 5 STM M5450 acting as a power shift register. It's an LED driver so
>it drives the optocouplers with no additional resistors.
>
>you need two pins for each m5450 (1 clock, 1 data)... i guess that you
>could also use MAX7300 parts and use only 2 pins because they
>are driven by I2C
>
>the el side of the circuit was powered by a single inverter.
>
>be warned that in certain conditions an rc network was needed on the
>triac side in order for it to switch off properly.
>
>
>have fun
>
>
>massimo