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sevisehda · 09-22-2003, 01:30 AM

I've been trying to figure out a way to monitor my fans speed while still controlling them. I think I finally found out how. I first trying it with a BasicStamp as to not accidently fry a fan header on my MB. Then tryed it on my DD5 and finally on my MB. They all worked, how well I'm not sure.

Basically I cracked open a fan then cut the traces between the main power input and the tach power input. I then soldered a 12v lead to the tach chip. This allows the fan to output a constant tach signal at 12v, while the fan can be supply either a pwm signal or a lower voltage.

The Basic Stamp gave me great results because it polled 5 times a second. Even after the fan power was removed it showed a nice decrease in RPMs until it went below 500 at which point iit reported ridiculous RPMS(above 40k). The DD5 gave some nice numbers but unfortuneately it won't display a single RPM for very long. Once I plugged into into the MB I ran MBM5 which polls every 10seconds. It showed some reasonable numbers as well.

Does anyone have any comments/suggestions to improve this, or is there an easier that I missed?

09-22-2003, 01:30 AM	#1
sevisehda Cooling Savant Join Date: May 2003 Location: NY Posts: 234	RPM monitoring with PWM? I've been trying to figure out a way to monitor my fans speed while still controlling them. I think I finally found out how. I first trying it with a BasicStamp as to not accidently fry a fan header on my MB. Then tryed it on my DD5 and finally on my MB. They all worked, how well I'm not sure. Basically I cracked open a fan then cut the traces between the main power input and the tach power input. I then soldered a 12v lead to the tach chip. This allows the fan to output a constant tach signal at 12v, while the fan can be supply either a pwm signal or a lower voltage. The Basic Stamp gave me great results because it polled 5 times a second. Even after the fan power was removed it showed a nice decrease in RPMs until it went below 500 at which point iit reported ridiculous RPMS(above 40k). The DD5 gave some nice numbers but unfortuneately it won't display a single RPM for very long. Once I plugged into into the MB I ran MBM5 which polls every 10seconds. It showed some reasonable numbers as well. Does anyone have any comments/suggestions to improve this, or is there an easier that I missed?