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G8MNY > TECH 29.02.16 10:46l 100 Lines 4799 Bytes #999 (0) @ WW
BID : 61890_GB7CIP
Read: GUEST
Subj: Fluorescent 12V Dimmers
Path: IW8PGT<IW7BFZ<I3XTY<I0OJJ<GB7CIP
Sent: 160229/0749Z @:GB7CIP.#32.GBR.EURO #:61890 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (New Aug 06)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
NEED
For /P operation a 12V fluorescent lamp is often too bright once your eyes get
acclimatised to the dark. This not only annoyingly attracts all flying moths in
the area, but also drains your battery more than needed. Here is a simple
modification that should work on most simple lamp designs.
Fuse On _______
+12VÄo-oÄÂÄo\oÄÄÂÄÄÄÂÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÂÄÄÄÄÄ¿ ||(_____ ³.
³ ³ SOT ³ ³ ³ )||( : \/ :
_³_ ³ R R pot 25V³+ === u1 )||( : :
/_\ \³ ³ 100k 220u=== ³______)||( : : Fluorescent
Idiot ³ T2ÃÄÁÄÄÄ´ ³ ³ ||( : : Lamp
Diode ³ e/³ \³<- Light ³ \³ ||( : :
³ ³ T3Ã<- Feed- ³ T1 ÃÄÄÄ¿ ||( : :
³ ³ e/³<- back ³ e/³ )||(___:_/\ :
³ ³ ³ ³ ³ ³ ||(_______³
³ +ÃÄÄÄÄÄÄÄÁÄÄÄ150êÄÄÄÄÄ)ÄÄÄÄ)ÄÄÄÄÄ´
-ve ³ 10u === Bias R ³ ³ 10n===
ÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÁÄÄÄÄÄÙ
HOW IT WORKS
T1 is the usual self oscillating power switching NPN (TAB or 2N3055). Instead
of say a 220ê bias R to +12V, a lower value 150ê is used in series with a
variable voltage/current supply. This consists of a switched volume control pot
(e.g. small edge wheel type) that also turns the lamp on, the pot is wired as a
variable R to be at minimum resistance on turn on, to ensure the lamp lights.
The current though this variable R controls the base drive of T2 (BC107), but
this drive can be shorted out by an optical NPN T3 (e.g. metal case TO92 NPN
with the top cut off). The optical feedback regulates on low brilliances only,
tending to reduce any flicker. T3 needs an aperture so see the lamp or to be
placed next to the tube to see its light.
Adjust the maximum value of the variable R with fixed 'Select On Test' R in
parallel to get a good no off dimming action. Try 47k - 2M SOT as needed.
RFI
If the inverter does not have a 220uF across the 12V, do add one, as it does
reduced the pulse current on the wiring (aerial). Do not put the fluorescent
lamps near aerials as it can make a good RF mixer as well as noise sources!
LAMP LIFE
Using a dimmed lamp may also extend lamp life, that is surprisingly sort on
these single ended pulse DC lit lamps. Remember to turn the lamp around to wear
out the other electrode to extend the lamp life!
Y don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
SB TECH @ WW
Fairy Light Flasher
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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