circuitry :
Here is a simple circuit that can produce the effect of
candle light in a normal electric bulb. A candle light, as we all know,
resembles a randomly flickering light. So, the objective of
this project activity is to produce a randomly flickering light effect in an
electric bulb.
To achieve this, the entire circuit can be divided into three parts. The first
part comprises IC1 (555), IC2 (74LS164), IC3 (74LS86), IC4 (74LS00) and the associated
components. These generate a randomly changing train of pulses.
The second part of the circuit consists of SCR1 (C106), an electric
bulb connected between anode of SCR1 and mains
live wire, and gate trigger circuit components. It is
basically half-wave AC power being supplied to the electric bulb.
The third part is the power supply circuit to generate regulated 5V
DC from 230V AC for random signal generator. It comprises a stepdown
transformer (X1), full-wave rectifier (diodes D3 and D4), filter capacitor
(C9), followed by a regulator (IC5). The random signal generator of
the circuit is built around an 8-bit serial in/parallel out shift register
(IC2). Different outputs of the shift register IC pass through a set of logic
gates (N1 through N5) and 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 timer (IC1). The clock frequency can be set using preset VR1
and VR2. It can be set around 100 Hz to provide better flickering effect in
the bulb.
The random signal triggers the gate of SCR1. The electric bulb gets
AC power only for the period for which SCR1 is fired. SCR1 is fired
only during the positive half cycles. Conduction of SCR1 depends upon
the gate triggering pin 3 of IC2, which is random. Thus, we see a flickering
effect in the light output. Assemble the circuit on a generalpurpose
PCB and enclose it in a suitable case. Fix bulb and neon bulb on the
front side of the cabinet. Also, connect a power cable for giving AC mains
supply to the circuit for operation. The circuit is ready to use.
Warning. Since the circuit uses 230V AC, care must be taken to avoid
electric shock
Here is a simple circuit that can produce the effect of
candle light in a normal electric bulb. A candle light, as we all know,
resembles a randomly flickering light. So, the objective of
this project activity is to produce a randomly flickering light effect in an
electric bulb.
To achieve this, the entire circuit can be divided into three parts. The first
part comprises IC1 (555), IC2 (74LS164), IC3 (74LS86), IC4 (74LS00) and the associated
components. These generate a randomly changing train of pulses.
The second part of the circuit consists of SCR1 (C106), an electric
bulb connected between anode of SCR1 and mains
live wire, and gate trigger circuit components. It is
basically half-wave AC power being supplied to the electric bulb.
The third part is the power supply circuit to generate regulated 5V
DC from 230V AC for random signal generator. It comprises a stepdown
transformer (X1), full-wave rectifier (diodes D3 and D4), filter capacitor
(C9), followed by a regulator (IC5). The random signal generator of
the circuit is built around an 8-bit serial in/parallel out shift register
(IC2). Different outputs of the shift register IC pass through a set of logic
gates (N1 through N5) and 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 timer (IC1). The clock frequency can be set using preset VR1
and VR2. It can be set around 100 Hz to provide better flickering effect in
the bulb.
The random signal triggers the gate of SCR1. The electric bulb gets
AC power only for the period for which SCR1 is fired. SCR1 is fired
only during the positive half cycles. Conduction of SCR1 depends upon
the gate triggering pin 3 of IC2, which is random. Thus, we see a flickering
effect in the light output. Assemble the circuit on a generalpurpose
PCB and enclose it in a suitable case. Fix bulb and neon bulb on the
front side of the cabinet. Also, connect a power cable for giving AC mains
supply to the circuit for operation. The circuit is ready to use.
Warning. Since the circuit uses 230V AC, care must be taken to avoid
electric shock
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