PWM FanBus for 8 Fans

I had plan build the ReoBus for my fans, but I had not place for 8 reostats. I build SW (by program) controled PWM FanBus.


  • PWM regs for 8 fans 12V/300mA (for each fan, may be increased)
  • PWM reg - minimum of heating
  • easy and low price
  • controled by RS232C (Serial port)

Control program

Ovládací klient

ShortCut for autopreset

(ShortCut for autopreset on the OS StartUp)

How to build


(Single side PCD with one wire overconnect)

(Component placement on the PCB)

Components list:

IO1 AT89C2051-24PI (with program flashed - see download) 45,-
IO2 ULN2801A 25,-
xtal 24MHz nebo 11,059MHz 15,-
T1 BC546B 2,-
D1 1N4148 1,-
R1, R2 2x 4k7 / 0,6W 2,-
R-SIP R-SIP 8x2k7 9pin (RR8x2k7) 4,-
C0 2uF / 25V 2,-
C1 100nF ceramic 2,-
Cx1, Cx2 2x 33pF ceramic 4,-
MOLEX connector MOLEX for wired 8,-
CANON 9F concector CANON 9F for wired 16,-
Fkon1-8 8x konektor PSH02-02P 12,-
socket DIL20 socket DIL20 4,-
PCB PCB (or universal driled PCB) 30,-
CELKEM ~ $6 US ~ 180 Kč ~ 180,-

Fotogallery will be later. Mail me about yours builded regulators.

Download of All (250kB)

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Next modifications

a) use single transistors, instead transistors array
b) use connection from picture at the rigth (e.g. Ro3=220R a To3=BD140 sink max. 750mA).
Only this is capable to use RPM monitoring, because fan is pernamently grounded.

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