MOVING MESSAGE DISPLAY

... how I can cascade it to make a 23 character. do I have to make another circuit of 8 character and cascade it to the first one or just extending the driver and add dot matrix led.
...and what are the use of DIP switches 1248. a simple block diagram may help with interconnection.

Hi dazheng,

You have downloaded my prev. attachment yet (LedDotMatrixProjects.zip). Plase read carefully the included original artikel in pdf format (you can found it in dir ori, in "Dot Matrix Display.zip", the file name is: E016048.pdf). Here are the answers to your questions (cascading, using the position switch, the 7 PNP line driver transistors, an NPN transistor interface to the paralell used serial inputs, the 330 Ohms for current limiting, are needed circuits in the reality, and basic examples for PC with a simple scrolling routine).
Do not forget the display clear character in my program is an ENTER (0Dh) instead of the original 0Ch.

However, if you have time and make a 24 char circuit in Proteus (it needed 3*5 = 15 pieces hc595) and post it here for me, I will write a stand alone scrolling program for this. It is possible with the hc595 beacuse it has output store registers.

Another remark: if the light of leds isn't enough beacuse of the multiplexing (theoretically and really 1/7 current), you can use other 8 stage shift regs with higher output current (eq tpic6b595 or mic5841bn) and a significant lower value of the current limiting resistors (33 or 47 Ohm instead of the 330 Ohm). The line driver PNP transistors must switch in this case higher current so you must use darlingtons here. Be careful!

zuisti