With speed-controlled cooling fans more often applied to intelligent equipment, there are some industrial equipment is also increasingly automated, speed-controlled cooling fans are also used more and more widely, speed-controlled fans have voltage resistance current and pwm speed control several ways, the following is a number of aspects to determine whether the cooling fan support pwm speed control function
1, look at the number of lines, the conventional cooling fan without function only positive and negative double line, with pwm speed control function of the cooling fan is three or four lines, three lines is in addition to the positive and negative line another is the pwm function line, four lines because the cooling fan with pwm speed control function at the same time may be with RD operation monitoring function, which forms four lines
2, look at the colour of the wire, cooling fan positive and negative pole is usually red and black, pwm speed control is blue, four lines to increase the function if the RD monitoring is generally yellow
3, observe the start-up state, PWM speed fan in the equipment standby time, can be maintained at a very low speed. The general speed is around one thousand revolutions, which greatly reduces the noise of operation. When the device is working, the fan speed can be seen to be significantly faster.
The other is the observation of the switch-on situation. The PWM temperature-controlled fan increases to its maximum speed at the moment of switch-on, lasts for a few seconds and then decreases to the low speed level of standby. This feature is also the most obvious characteristic of PWM intelligent temperature control fans, and can be used to determine whether the fan and the motherboard really have PWM functionality, or whether its functionality is faulty
