Welcome LED Display Board Circuit

We offer Welcome LED Display Board Circuit  that is designed using 5/3mm LEDs which, flashes each character one after another. Hobbyists can use this simple, low cost and effective ‘WELCOME’ Display Board at many places for decoration purpose. One can also change the alphabets by arranging the number of LEDs as shown in the circuit diagram. In speller displays each letter of the sign glows one after another until all are “ON”. After a few seconds, they will go out one by one and repeat thereafter.
About the Circuit :
The circuit is built around shift register IC3, which has eight outputs. Every eight speller are driven by eight outputs. IC3 consists of two identical 4-stage serial-input/parallel output registers. Each register has independent CLOCK and RESET input as well as a single serial DATA input. The logic level present at the DATA input at pin7 of IC3 is transferred into the first register stage and shifted by one stage at each positive going clock transition. Resetting of all stages is accomplished by a high level on the reset line. The clock circuit is designed around IC1, which provides clock input to IC3 at pin1 and pin9. The duration of the clock pulse is determined by timing components R1-R2/P1-C1. Adjusting preset P1 can change this frequency, which in turn change the speed of spelling output. At every clock transition, output of IC3 goes on shifting. IC2 is designed to provide data input to IC3. For correct logic data input, preset P2 is adjusted. Output of IC3 drives transistor T1 to T8 to light the letter composed of from LEDs on display board. Diodes D1, D2 and capacitor C7 is used for DC rectifier circuit. You can fabricate desired letters/alphabets out of LEDs by adjusting suitable PCB.