Simple and easy to use electronic candle circuit diagram

This is a simple and easy to use electronic candle circuit built using TTL ( Transistor -Transistor Logic) of 74LS164, 74LS86 and 74LS00. This circuit will produce a candle light effect in a normal 220V electric light bulb. As we all know, candle light resembles a random flickering light. So the goal of this project activity is to produce a random flickering light effect in an electric light bulb.

The whole circuit can be divided into three parts:

The first part consists of IC 1 (555), IC2 (74LS164), IC3 (74LS86), IC4 (74LS00) and associated parts . These produce a randomly varying pulse train.

The second part of the circuit consists of SCR1 (C106), a light bulb connected between the anode of SCR1 and the hot wire of the power supply , and the gate trigger circuit components. It is basically a half wave AC supplied to the light bulb.

The third part is the power adapter circuit, which is used to generate a regulated 5V DC from the 230V AC for the random signal generator. It consists of a step-down transformer (X1), a full-wave rectifier ( diodes D3 and D4), a filter capacitor (C9), and then a voltage regulator (IC5).

The random signal generator of this circuit is built around an 8-bit serial input/parallel output shift register (IC2). The different outputs of the shift register IC pass through a set of logic gates (N1 to N5) and the final output appearing at pin 6 of gate N5 is fed back to the inputs of pins 1 and 2 of IC2. The clock signal appears at pin 8 of IC2 which is clocked by an astable multivibrator configured around a timer (IC1) . The clock frequency can be set using the preset VR 1 and VR2. It can be set around 100Hz to provide a better flickering effect in the bulb.

The random signal triggers the gate of SCR1. The light bulb gets AC power only during the period when SCR1 is ignited. SCR1 is triggered only during the positive half cycle. The conduction of SCR1 depends on the gate trigger pin 3 of IC2, which is random. Hence, we see a flickering effect in the light output.

Assemble the circuit on a general purpose PCB and enclose it in a suitable housing. Fix the bulb and neon light on the front of the cabinet. Also, connect a power cord to provide AC power to the circuit for operation. The circuit is ready for use.