Going to mod variable resistors onto fans. What resistance?

Control: management of fans, temp/rpm monitoring via soft/hardware

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WARDOZER9
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Going to mod variable resistors onto fans. What resistance?

Post by WARDOZER9 » Fri Feb 18, 2011 6:33 am

I just ordered 2x Yate D12SL's and when they get here I'm going to mount a variable resistor onto the fan body and cut and solder the wires onto the resistor to be able to tune each fan individually for best results and have that change permanent for each fan.

Any suggestions on what kind of resistance I should go for in the variable resistors? I probably won't be needing to go down to 5v as 7 - 8v seems to be the sweet spot for these fans.
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Vicotnik
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Re: Going to mod variable resistors onto fans. What resistan

Post by Vicotnik » Fri Feb 18, 2011 7:17 am

That's a very inefficient way to control the fans. Why not get a couple of FanMates? Or if you want to build it yourself it's easy to build a simple rheobus.
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WARDOZER9
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Re: Going to mod variable resistors onto fans. What resistan

Post by WARDOZER9 » Fri Feb 18, 2011 7:24 am

Basically I want something to do and if I use this method then when I tune each fan that setting will stay with the fan the rest of it's life reguardless of what PC it goes into down the road. Plus with mounting it to the fan body it won't be in the way.
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Re: Going to mod variable resistors onto fans. What resistan

Post by Vicotnik » Fri Feb 18, 2011 7:53 am

You will need a pretty beefy resistor and it will give off a lot of heat. Such variable resistors are often quite expensive. With a rheobus solution you need basically a cheap transistor and a cheap variable resistor that don't need to handle a lot of current. The transistor will give off a little heat but less so than a resistor would.
Mounting the solution in the fan body will be difficult either way. I don't think it's feasible.

A marked Fanmate with the setting tuned and the knob fixed in place with some hot glue? That would make it kind of permanent. Or you could build something similar for less money if you feel like tinkering.

edit: A fixed resistor would be inefficient but compact and cheap. If the fans sounds fine at 7v then perhaps the 7v-trick? That's easy and efficient.
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alleycat
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Re: Going to mod variable resistors onto fans. What resistan

Post by alleycat » Fri Feb 18, 2011 9:34 pm

I built something like this using a rotary switch and some rectifier diodes.

WARDOZER9
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Re: Going to mod variable resistors onto fans. What resistan

Post by WARDOZER9 » Sun Feb 20, 2011 9:29 am

alleycat wrote:I built something like this using a rotary switch and some rectifier diodes.
Any pics or further details on your mod?
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Re: Going to mod variable resistors onto fans. What resistan

Post by Vicotnik » Sun Feb 20, 2011 9:47 am

You can connect rectifier diodes in series with the fan to get a voltage drop (~0.7v per diode). The rotary switch would then control the number of diodes and you would get variable control but in 0.7v steps (or n*0.7v).
This is one of the more efficient solutions, less waste heat compared with using a resistor.
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Re: Going to mod variable resistors onto fans. What resistan

Post by LM741C » Sun Feb 20, 2011 12:40 pm

WARDOZER9 wrote:I just ordered 2x Yate D12SL's and when they get here I'm going to mount a variable resistor onto the fan body and cut and solder the wires onto the resistor to be able to tune each fan individually for best results and have that change permanent for each fan.

Any suggestions on what kind of resistance I should go for in the variable resistors? I probably won't be needing to go down to 5v as 7 - 8v seems to be the sweet spot for these fans.
It depends on the number of amps the fan draws. The YL's are rated at .3 amps but that's probably max draw during startup. If they are anywhere like the Nexus fans, mine draws 0.081 amps at 12v (runtime) and 0.052 amps at 7v so you're looking at approximately 95ohms. I would say 50-200ohms variable resistor should do the trick.

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