- on Computer/Software/Internet
- Published in issue 7/2010 on page 56
3-Pin Fan in 4-Pin Socket
(Summer Circuits 2010 article)
The most recent PC motherboards provide four pin connectors for cooling fans especially for the CPU fan. The older three pin fans are controlled by varying their DC voltage. The fourth pin on the newer connectors supplies a PWM signal to control fan speed. A three pin fan can be plugged into the four pin connector but with its fixed 12 V supply it runs at full speed all the time the PC is switched on.