Here is a basic circuit of Christmas
star that can be easily constructed even by a novice. The main
MAINS-OPERATED CHRISTMAS STAR SANI THEO PRINCE PHILLIPS advantage of
this circuit is that it doesn’t require any step-down transformer
or ICs.
Components like resistors R1 and R2,
capacitors C1, C2, and C3, diodes D1 and D2, and zener ZD1 are used
to develop a fairly steady 5V DC supply voltage that provides the
required current to operate the multivibrator circuit and trigger
triac BT136 via LED1.
The multivibrator circuit is
constructed using two BC548 transistors (T1 and T2) and some passive
components. The frequency of the multivibrator circuit is controlled
by capacitors C4 and C5 and resistors R3 through R7.
The output of the multivibrator circuit
is connected to transistor T3, which, in turn, drives the triac via
LED1. During positive half cycles of the multivibrator’s output,
transistor T3 energises triac BT136 and the lamp glows.
Circuit Diagram Below:
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