Hi all,
Over the last couple of days I have been trying to use my motherboards FAN PWM output to switch a 12v line down, but I cant really manage to adjust the FAN. I have added a diagram here.
The thing is that when I use a LED it seems to work perfectly lighting up and down when I adjust dutycycle in bios, but when it comes to the fan it seems to stay at full speed, not adjusting up and down.
As far as I know the PWM wire will use a PWM frequency of about 25khz and something between 3.3v to 5v. When its on, it should make the PWM low, meaning that if the wire is not connected the fan should run full speed. Since my only FETS are Logic Level N-Channel fets, I use a PNP transistor to turn that around. When its on, the FET should open, when off it should close. Can anyone here tell me what can be the problem?
**broken link removed**
I have been thinking that I might switch things too fast for a non-pwm FAN in case the FAN have a build in capacitor or something, but I have no idea if that can be the reason.
Anyone?
Over the last couple of days I have been trying to use my motherboards FAN PWM output to switch a 12v line down, but I cant really manage to adjust the FAN. I have added a diagram here.
The thing is that when I use a LED it seems to work perfectly lighting up and down when I adjust dutycycle in bios, but when it comes to the fan it seems to stay at full speed, not adjusting up and down.
As far as I know the PWM wire will use a PWM frequency of about 25khz and something between 3.3v to 5v. When its on, it should make the PWM low, meaning that if the wire is not connected the fan should run full speed. Since my only FETS are Logic Level N-Channel fets, I use a PNP transistor to turn that around. When its on, the FET should open, when off it should close. Can anyone here tell me what can be the problem?
**broken link removed**
I have been thinking that I might switch things too fast for a non-pwm FAN in case the FAN have a build in capacitor or something, but I have no idea if that can be the reason.
Anyone?