What is your scan rate?
The SCRs won't turn off until the end of the mains 1/2 cycle so if you are
scanning much faster than this you will not be able to turn them off fast
enough.
If you are scanning each collumn at or below mains frequency then I would
expect noticable flicker.

Richard










At 07:53 PM 2/16/02 +0700, you wrote:
>[EE]:
>Firstly, thank you for all comments on my question about
>how to drive 8 x 128 leds matrix brightly.
>
>Now I'd like to change all the leds to a 5 watts 220 volt bulb,
>so the matrix become an 8 x 128 5watt 220 volt.

Okay.

>I have tried with a SCR connected to every bulb, but the bulb
>lights each column (8), does not behave as a LED. When the position
>is changed, the it lights each row (128).

You have 1024 SCRs?

(It's possible to multiplex bulbs, but the currents and voltages can
get out of hand very quickly)

If you have 1024 SCRs, the easiest way to drive them would probably
be with a static drive of some sort- say a latched SR with 1024 outputs.
Presumably you are feeding the load with full-wave rectified 240V/50Hz
so the SCRs will commutate at the end of the mains cycle.

Best regards, 7

Spehro Pefhany --"it's the network..."            "The Journey is the
reward"
speff@interlog.com             Info for manufacturers:
http://www.trexon.com
Embedded software/hardware/analog  Info for designers:
http://www.speff.com
9/11 United we Stand

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