I suspect you may have some problems multiplexing incandscent lamps due to the high thermal inertia of a lamp filament. A lamp will take a significant amount of time to turn on to full brightness, this will severly limit the speed that they can be switched at. Also thermal stress will cause premature lamp failure. You may be able to overcome both of these by ensuring a continuous low current flows through the lamps, keeping the filaments hot (but not incandescent). However, this will make matrix switching somewhat tricky.
You could avoid multiplexing and use 35 triacs controled by a few shift registers cascaded together. If the light bulbs aren't high power (<60 watts) you could use TO92 cased triacs to save space.
-----Original Message-----
From: Gabriel Callao [SMTP:gcaffese@YAHOO.COM]
Sent: Thursday, November 11, 1999 1:19 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: 220volt lamp matrix
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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