How do you keep this Enermax Thermo Control Fan from spinning <3000rpms?

[optimistic]

I bought the Enermax Thermo Control fan because of it's execellent noise to cfm ratio. Anways, in order for the Enermax to spin at top speed the sensor diode must detect a case temp of 85C!!!!! WTF?!?! My case would have to be on FIRE for those kind of temps!

85C - 3100 RPM
65C - 2600 RPM
45C - 2100 RPM
25C - 1800 RPM

I heard by cutting off the sensor, the fan will spin at 3100RPM. Will it work? Need a confirmation please.


---------------------
ABIT KT7A
AMD Thunderbird AVIA 1200MHz no OC
256 MB of Mircon Cl3 PC133
PAL6035 w/ Sunon 27CFM 34DBA
Enermax Thermo Control 2x80mm
Enermax CS-A1QX-06 Case
Enermax EG301P-VB (300W) PSU

 

[sitka]

yep here

 

[Jhhnn]

From my own experience with their temp controlled psu fans, I would say that shorting the leads together would give max rpm. It uses a thermistor sensor, the resistance goes down as the temp goes up. Go ahead and play around with it, I doubt it can be damaged just fooling with the sensor wires. Wiring a small 50K potentiometer in parallel with the sensor would allow for adjustable higher speed at ambient while maintaining temp controlled variable speed.

 

[sitka]

That particular fan has a sensor that exhibits 11K ohm at room temp.

 

[weovpac]

take a look at this:Hal-Tech

 

[Pabster]

Optimistic wrote:

&quot;I heard by cutting off the sensor, the fan will spin at 3100RPM. Will it work? Need a confirmation please.&quot;

Yes, but you've got to tie the 2 white leads together. I didn't solder, just twist and either use a cap or some electrical tape. These aren't exactly high voltage or high current devices

 

[NCstateBen]

I belive that you can keep the thermo contol but change the power curve so that the fan spins faster at lower temps by adding another resistor in parallel with the thermistor.

The equation for total resistance in a parallel circuit is:

1/resistor1 + 1/resistor2 = 1/total resistance

So say hypothetically, the thermistor varries between 5 and 15 ohms, and you splice a 10 ohm resistor in parallel to the curcuit. The total resistance when the thermistor is 5 ohms is then:

1/5 + 1/10 = 3/10

The total resistance is then 10/3, or 3.333 ohms, which of course, is less than 5.

At 15 ohms:

1/15 + 1/10 = 1/6

The total resistance is then 6 ohms, which is much less than 15.


I may be wrong, but according to the math, this is how it should work. You would just have to figure out how big a resistor to add. If the resistor is too big, it wont do anything. If it is too small, you wont get as much effect out of the thermistor. I have never actually tried this but I have one of these fans and will probably try it if I can figure out what how big a resistor I need. Can anyone confirm that this works?

 

[Jhhnn]

Like I said in my post above, Ben, using a small 50K ohm varistor lets you dial in any resistance(rpm) you want. At 50K in parallel with 11K the total resistance is 11.1K, at zero, the total is zero. Use a multi-turn one intended for pcb mounting to get very fine control over the low speed setting. The current flow is extremely small, I'm sure, so $.59 at the shack should do it. Have fun.