Control box fan as case fan from Asus mbd plug

honegod

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Put relays in place of rotary switch. Have motherboard pwm fan socket tell relays to turn fan on and regulate speeds per my settings in fan program.

The bit that plugs into the fan socket, that controls the relays = X.

Help.
 

honegod

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So I will need a bit to simulate a tach signal TO the board saying that the fake fan is running at the right speed setting, and a second bit that senses the pulse rate FROM the board and generates a power on signal to the appropriate relay.

The tach sender bit is covered in another post. (Or I could put a tach fan in the airflow of the big fan and get a signal from it ?)
But I'm blank on the relay selector bit.
 

Dayaks

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What is the purpose of this? Why not just buy the proper fan, what does that fan get you?

If you need high CFM delta makes them for cases.
 
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honegod

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It is the right fan for the concept.
Swapping in a better motor in the future is good, but it is the correct form factor, airflow, and non PSU powered.

This controller is for [H]ardness sake.
 

honegod

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The idea is to have a stupid immense airfilter setup with the entire computer inside of it.
The box fan makes up one of the 6 sides with 4 sides being filters layered 2 deep.
Outer layer a coarse blue fiberglass prefilter protecting a ooper Dooper hepaish inner layer.

Mounting the components to the 6th side (bottom) in a Spock style 3D chessboard setup puts everything in nice clean airflow.

With motherboard temperature sensor controlled fans to focus spot cooling as needed it would be sweet to be able to ramp up the overall flow through the 'case' WITHOUT having to manually twist a knob, eh?
 

Fenris_Ulf

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This strikes me as an overall bad idea. If you don't know enough to ask questions with even somewhat appropriate terminology, you're probably in over your head and shouldn't be messing with lethal voltages.

Now that the disclaimer is out of the way, there's two ways to do this.

The first is to use a RC network to smooth out the PWM output to more closely represent an analog output. Use this as a signal in to an Arduino that has four outputs for relays. You will probably need to buffer the relay coils with transistors since sufficiently beefy relays may be more than an Arduino can handle natively.

Here's a page with a pinout for the fan control: http://www.brettcave.net/howto/circuits/windturbine-boxfan/

You will need to use one relay for each switch position and make sure only one is flipped at a time. It's still going to be fiddly to get it to work right.

A second method to do this:
Ditch the box fan. Get an electric automotive radiator fan of appropriate size. They run off of 12v, so no high voltages required. Use the circuit here:
https://www.techpowerup.com/forums/threads/so-you-want-pwm-control-of-your-3-pin-fan.115752/
to control your fan speed based off of the PWM signal from the mobo. Beefier MOSFETs might be required than those in the link and you would want to wire to the power supply rather than the mobo header for power.
 
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