Self-Writing LED Display Sign Controller
This is a circuit of self-writing LED display sign controller. This circuit consist of eight power shift register which are installed in cascade. The shift registers are used to turn on a string of 64 lamps or LEDs sequentially. Here is the circuit :
When the shift register clock (SRCK) is clocked, the register is clocked, so that the display is update after each bit of data is shifted in. The LEDs strobe on from left to right and until the LEDs strobe off in the same manner because of the serial input data (SER IN) is held alternately high and low for any period greater than 64 clocks. The display sign is dynamic and attractive because the LEDs arranged sequentially as in written message.
This circuit uses LM556 timer to generate the clocks and requires only one IC in addition to the shift register. To blanking or blinking the LEDs, this circuit uses the output enable. [Source: Texas Instruments Application Report]