> Regarding to the matrixes, I've always noticed that most of those 
> led
> signs are usually 5x7 characters. I have no idea why. even 
> 44780-based
> LCDs

In the goode olde days when displays were very very very expensive to 
make and dot matrix printers were trying to take over from fixed 
character printers (such as daisy wheel, golf-ball, chain, band, etc) 
and also very very expensive, it was desirable to make characters 
using as few dots as possible. It was determined that 5 horizontal by 
7 vertical was about as small a character matrix as you could get 
without doing excessive violence to the appearance. You can go smaller 
and be recognisable BUT it is immediately obvious that you are doing 
strange things. 5 x 7 usually looks really bad but the characters are 
instantly recognisable. You CAN produce largely recognisable 
characters using a 7 segment display! OK for the initiated to 
recognise but essentially unusable by Joe Average.


        RM


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