Four years ago, I launched a new series of moving message sign mainly for outdoor. Reliability and simplicity were the most concerned.
The LED type I used is the red bright one rated @20mA (the number of LEDs in one pixel depends on sign size).
I decided to drive the LEDs with a DC current (in the range of 15 to 20mA) when an LED is on during the frame period.
This was possible by cascading "16-bit Constant Current LED Sink Driver" ICs. The Chinese factory which produced my modules suggested MBI5026 (made in China but it turned out be a good one).
The interface of these driver ICs is made compatible to SPI (serial peripheral interface) which my available Atmel AT89C8252, AT89C8253 and SST89E58RDA uC have.
At a rate of 30 frames/sec, up to 4096 LEDs could be refreshed (though my software is not yet optimized).
It is just an idea.
Kerim
Off topic:
I designed my first moving sign in 1979. Its pixel was 40W 220Vac bulb driven by a triac. Its controller was made using Z80 and 27C512 EPROM.
Soon later, my first LED sign was 64 x 7 based on scanning (also for Arabic messages for which I create a special font that needs only 7-pixel height). The LED was pulsed with 400mA! The duty cycle was 1/64. Although these small signs lived for many years, I won't do again now
In fact, the static mode lets the design be rather simple, flexible and reliable. So while most of my last series signs usually run 24/7, some of them are 4 years old now