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G8MNY > TECH 27.01.26 16:51l 64 Lines 2531 Bytes #9 (0) @ WW
BID : 50728_GB7CIP
Subj: Variable Speed Thermal Fan
Path: JH4XSY<N3HYM<GB7YEW<GB7CIP
Sent: 260127/0750Z @:GB7CIP.#32.GBR.EURO #:50728 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Jul 15)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
I have often been annoyed by fan noise from over powerful fans in gear. Here is
a solution I adopted for a 12V PSUs & 400W HF PAs. Small 12V fans can be found
in a scrap PCs etc. and draw about 70-100mA depending on speed & size.
2x PNP CIRCUIT (Germanium NPN can be used E-C reversed)
use idiot diode & fuse if fan manually wired up.
ﾚﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｴ<ﾃﾄo-oﾄﾄ +12V
e\ｳSilicon
PNPﾃﾄﾄｿ FANS
/ｳ e\ｳPNP Small ﾚﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｿ
ｳ ﾃ Germanium Sponge fill ｳ Tabｳ~ｳ ｳ
ｳ /ｳbetween fins gap so fan..ﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾅﾄﾅﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾙ.
ﾃﾄﾄﾄﾄﾙ blades kept ﾞ ﾞ ﾞ ﾞ ﾞ ﾞ ﾞｺﾞ ﾞ ﾞ ﾞ ﾞ ﾞ ﾞ
_ｳ_ away from ﾞ ﾞ ﾞ ﾞ ﾞ ﾞ ﾞｲﾞ ﾞ ﾞ ﾞ ﾞ ﾞ ﾞ
/ + \ For a quieter fan, fins for ﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛﾛ
ｳ 12V ｳ try 2 in series, min noise. ｳ ｳ
\FAN/ or use a 24V one! ｳ P A / P S U ｳ
~ｳ~ ｳ ｳ
ﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄ 0V ﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾙ
It uses a high gain (x100) tab silicon NPN or PNP controlled by a leaky
Germanium PNP or NPN placed between the hot heatsink fins (test a germanium
with a soldering iron for resistance change and Fans on/off). I used an all
plasic Tab silicon cable tied to the fans, with the insulated geramanium
transistor E & C leads twisted (make sure it's case is isolated or insulate)
and exposed connections in heat shrink etc.
Fan operation is typically from @ 50 with a slow variable speed action until
cool!
The fan can be in the earth path or +12V side...
Silicon NPN & Germanium PNP CIRCUIT
ﾚﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｴ<ﾃﾄo-oﾄﾄ +12V
_ｳ_
/ + \ For a quieter fan,
ｳ 12V ｳ try using 2 in series,
\FAN/ or use a 24V one!
~ｳ~
ﾃﾄﾄﾄﾄｿ
ｳ e\ｳPNP Small
ｳ ﾃ Germanium
\ｳ /ｳbetweens fins
NPNﾃﾄﾄﾙ
e/ｳSilicon
ﾀﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄ 0V
RESULT
In high use (waffle mode with processing on or a pile up) the fan starts up and
runs very quietly from about 5V across it, and gently runs faster if the
heatsink gets hotter.
See TECH bul "PA & PSU Fan Noise"
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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