Dc cooling fan equipment which has a lot of line, here we introduce some of the output signal of dc cooling fan.
Fan cooling fan equipment can match various sizes of FG or RD signal lines. The cooling fan has two lines, three lines, four lines. Two line is is the cathode, in addition to three pole is negative for other signal lines, and line has two kinds: one kind is FG, namely speed signal, a square wave signal, generally for the fan to the end of the signal frequency * 30 = fan speed, there will be no actual speed is slow. Another kind is the RD signal, its function is fan operation output low level, fan does not turn output high level, the CPU by detecting the signal to go to learn that the fan is normal operation.
Four wire cooling fan, in addition to the positive and negative and FG, another general line for the PWM, from now on line input of the PWM duty cycle change signal can adjust the fan speed, speed and basic duty ratio change is linear, generally does not change significantly in the high-end. Change curve are also associated with cooling fans inside circuit design, can achieve different adjusting range.
