G8MNY  > TECH     15.04.25 09:30z 45 Lines 2119 Bytes #177 (0) @ WW
BID : 30330_GB7CIP
Subj: Fairy Light Flasher
Path: ED1ZAC<ED1ZAC<IZ3LSV<I0OJJ<N6RME<CX2SA<VE3CGR<GB7YEW<GB7CIP
Sent: 250415/0912Z @:GB7CIP.#32.GBR.EURO #:30330 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

By G8MNY                                (New Feb 10)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
This is a simple design used to flash a low power mains Christmas tree fairy
light set. The unit is in the shape of a bell & plugs in instead of a lamp.

CIRCUIT
                5x 1N4007ÚÄÄÄÂÄÄÄÂÄÄÄÄÄÄÄÂÄÄÄÄÄÄ¿
                        _³_ _³_ _³_      ³      ³
                        /_\ /_\ /_\    100K     ³             ÞÝ
                         ³   ³   ³ Disc  ³Charge³            _±±_
LÄÄFuse-bulbsÄ<<ÄÄÂÄ100RÄ´   ³  20K      ³      ³          /~    ~\
   Bulb          ===     ³   ³   ÃÄÄÄÄÄÄÄ´      ³         Þ        Ý
               u1 ³      ³   ³   ³      62K     ³         ³  PCB   ³
              400V³      ³   ³   ³       ³      ³         ³³      ³³
                  )||    ³   ³   ³      _³_Neon ³         ݳ      ³Þ
                  )||L   ³   ³   ³     /_³_\    ³        Þ ³      ³ Ý
                  )||    ³   ³   ³    (ù___ )   ³       /  ÀÄÄÄÄÄÄÙ  \
NÄÄÄÄÄÄÄÄÄÄÄÄÄ<<ÄÄÁÄÄÄÄÄÄ)ÄÄÄ´  +³     \_³_/    ³
                        _³_ _³_ ===      ³    ³/
                        /_\ /_\  ³10u    ÃÄÄÄÄ´ 2SC106D
                         ³   ³   ³160V  20K   ³\e NPN
                         ÀÄÄÄÁÄÄÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÙ
HOW IT WORKS
This basically a neon & capacitor timebase aided by the transistor. To work on
AC mains there is a bridge rectifier & also 2 mains filter components.

On powering the lamps are off & the 10uF charges up via the 100K (off time).
When it has reached the neon striking voltage (85V) current flows through the
neon to the transistor base. The transistor conducts & shorts out the flasher
supply making the lamps some on. The transistor stays on until the neon goes
out @ about 70V from the 10uF. The on time is determined by the discharge
through the 62K+neon, & also diode & 20K route.
The other 20K ensured the transistor is kept properly off when the neon is out.


See my TECH bul on "Christmas Mains Light Chains" & "Night Light Switch"


Why don't U send an interesting bul?

73 De John, G8MNY @ GB7CIP


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