Multi Color Led Circuit Diagram

Introduction

A two-colour LED consists of two light-emit- ting diodes, usually red and green, encapsu- lated in the same case. It has three pins: two for the anodes, and one for the common cathode. In this way, each diode can be activated separately. Various colours may be obtained by varying the current through one or both of the diodes. For example, four colours may be obtained when the currents. are arranged as follows: red, green, orange R 21G) and yellow (IG-21R). This Multi Color Led Circuit is very easy to build at home with 4503 and 4025 ICs.

In the present circuit, the diodes are driv- en by CMOS three-state buffers Type 4503, which, unlike most CMOS ICs from the 4000 series, are capable of supplying an output current of up to 10 mA. The currents are lim- ited by resistors R1-R6, whose values should be ascertained empirically for brightness and colours according to requirements.

Circuit Diagram of Multi Color Led Circuit

The Multi Color Led Circuit can be designed using a few basic components. The circuit diagram of this project is shown below.

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Explanation of Multi Color Led Circuit

The circuit was originally developed to indicate the state of three inputs, a, b, and c (non-binary, i. e, only one of these is at 1 at any time), with the configuration (a-b-c=0) represent- ing the fourth state. The latter is decoded by NAND gate IC1. An additional effect is produced by gates IC1a and IC16, which form an oscillator circuit that outputs about two pulses per second. These pulses are used to control the common-enable input, DA (pin 1) of IC2 so as to produce a flickering effect. The oscillator is controlled via inputs d and e. Pulling both of these logic high disables the oscillator and the LED driver. With e=0 and d-1 the outputs of IC2 are switched to three-state, and the circuit is in power- down standby mode.

Although designed for a 12-V supply voltage, the circuit will work with supply voltages between 5 V ond 16 V. Non-used inputs of CMOS ICs must, of course, be tied to ground via 10-100 k2 resistors