Bi Color LED

This circuit uses Bi-color LED which creates an eye-catching running display effect. This project can be used in the places like borders of animation, pictures, short word display etc. The bi-color LEDs are similar to uni-color with the difference that there are two LEDs housed in a package. Bi-colour LEDs may have two or three leads depending upon the internal connections. The circuit is based on CD 4017 whose pinout has been shown below:

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Fig. 1: Pin Diagram OF CD 4017 ICs

The base of the circuit is made around the IC’s 555 and CD4017. IC 555 works in astable mode. It provides low frequency clock pulse to sequential decade counter. The output of IC CD4017 changes in sequence with each pulse from IC 555. CD4017 is a decade counter which have 10 decade outputs and the input includes CLOCK, RESET and a clock inhibit signal.

In this circuit five Bi-color LEDs are used. The LEDs first light in green color, from top to bottom and then in red color, from bottom to top. The IC1 provide clock pulses to the input of decade counter IC2. At each clock pulse, IC2 counts from 0 to 9. The first five pulses lights up in green color when they reach the green anodes of the bi-color LED. Similarly, next five pulses lights up in red color when they reach the red color anodes. The next positive clock pulse to the 4017 resets the IC to zero and this process continues.

The glowing speed of the LEDs can be controlled by the use of potentiometer (R2). Moderate speed should be selected for the best results in this project.