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Old 23rd Aug 2019, 10:02 pm   #20
mhennessy
Dekatron
 
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
Default Re: Fan speed control by OP of amp.

Usually, the 2 extra wires on 4 wire fans are for tacho out and PWM in.

http://pavouk.org/hw/fan/en_fan4wire.html
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