USB Fan Speed Controller

[oskupc]

I have two usb 40mm 5V fans,

because their speed are too slow, i want to control their speed with usb fan speed controller with this https://www.ebay.com/itm/144136050818

 

i want to buy 2 of it, and plug them to my motherboard,

but can them damage my motherboard?

 

this the picture of the controller, thanks.

Spoiler

 

[SorryBella]

1 hour ago, oskupc said:

but can them damage my motherboard?

More concerned with the fan as the spec says it accepts 4-12V input.

[oskupc]

28 minutes ago, SorryBella said:

More concerned with the fan as the spec says it accepts 4-12V input.

i may not understand, it is ok if the fans get damaged,

but does that means there is no problem to my motherboard?

[Biohazard777]

4 minutes ago, SorryBella said:

More concerned with the fan as the spec says it accepts 4-12V input.

That is the accepted voltage input range of the controller, output is 2.5-8V.

But yeah, even 8V could damage 5V fans.
The fan will certainly die prematurely.

There is another problem with running DC motors at higher voltage than what they are rated for...
Increasing voltage also increases the current and torque,
double the voltage and it will double the current draw, resulting in x4 the power.

^ a bit simplified, but still relevant

 

1 hour ago, oskupc said:

I have two usb 40mm 5V fans,

 

Amps / current?
 

As for your mobo, output voltage of your speed controller is irrelevant, but how much current you try to push through your USB port could lead to damage.

I'd expect the controller to die 1st though, how it dies could affect your mobo.
I could explain further, but I've got a feeling that isn't why you are here.

 

TL;DR

You might be fine, but you are operating out of spec... and that is something I could never recommend.
If the fans are "slow" (not pushing enough air) at what they are rated for, the way you fix that is by getting better fans (FYI:  Noctua makes 5V fans).

[oskupc]

3 minutes ago, Biohazard777 said:

That is the accepted voltage input range of the controller, output is 2.5-8V.

But yeah, even 8V could damage 5V fans.
The fan will certainly die prematurely.

There is another problem with running DC motors at higher voltage than what they are rated for...
Increasing voltage also increases the current and torque,
double the voltage and it will double the current draw, resulting in x4 the power.

^ a bit simplified, but still relevant

 

Amps / current?
 

As for your mobo, output voltage of your speed controller is irrelevant, but how much current you try to push through your USB port could lead to damage.

I'd expect the controller to die 1st though, how it dies could affect your mobo.
I could explain further, but I've got a feeling that isn't why you are here.

 

TL;DR

You might be fine, but you are operating out of spec... and that is something I could never recommend.
If the fans are "slow" (not pushing enough air) at what they are rated for, the way you fix that is by getting better fans (FYI:  Noctua makes 5V fans).

i think i will forget abot these 5v fans,

if i buy a 2-pin 12v or 24V fan like these: https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313&_nkw=40mm+fan&_sacat=0

and since it is a 2-pin fan

can i use 4-pin to molex converter?

 

 

[Biohazard777]

1 hour ago, oskupc said:

i think i will forget abot these 5v fans,

if i buy a 2-pin 12v or 24V fan like these: https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313&_nkw=40mm+fan&_sacat=0

and since it is a 2-pin fan

can i use 4-pin to molex converter?

Well 1st of all, the link leads to ebay search (not a specific product).

I'll break up the response in two parts:

 

1) Physical connection

I'm gonna use the 1st search result (for me): https://www.ebay.com/itm/255662305595

 

Pay attention to the connector:

Sadly the description doesn't say what kind of connector that is:

2-pin, yeah no shit...

That is a very small 2pin connector, if you want to use that connector with regular fan connectors found in a PC:

You will quickly notice the fit isn't right (the pitch is probably gonna be too small on the male side), it is too shallow, and the "lock" doesn't align (even if you could jam it in there it won't be secure).
So you'd either have to get another adapter for that as well or cut the cables and splice the wires manually.

------

( I'm intentionally not gonna name all the possible connector types, makes this conversation harder to follow and you can pretty much visually spot when something isn't gonna fit )

------

Or.. you could buy a 3 pin fan with a "normal" connector:
https://www.ebay.com/itm/142673032310

As and added bonus this one will report speed (thanks to the 3rd signal/tach wire). More about that in part #2.

 

Anyhow even if you mess up and order with the fan with the wrong connector it won't be the end of the world, you can always cut the wires and splice them manually.

2) Wiring
You can use a molex to 3 pin or 4 pin fan adapter (doesn't matter, I explain why further bellow), and a 12V fan.
Because molex carries 12V (it also carries 5V but that is irrelevant for your use-case):

If you try it with 24V fan it either will not spin up at all, or if it does it would run slow... so do not buy a 24V fan.

 

As for pins, 2 pin fan means it only has + and -. These fans do not report how fast they are spinning, the only way to control their speed is by changing voltage.
3 pin fan means it has +, -,  and sense (aka tach / tachometric signal) wire, that wire reports back how fast the fan is spinning. These fans are also voltage controlled.
4 pin fan means it has +, -, sense, and PWM control (signal wire that tells the fan to turn on/off very quickly, thus controlling speed).

 

So that is why it doesn't matter if you use a molex to 3 pin or 4 pin fan adapter.
You will not be using PWM to control their speed, nor do you have a tach wire to read the actual speed of the fan.

2-pin 12V fan will constantly work at fixed voltage of 12V provided by molex.

 

May I ask what do you want to cool with those fans?
Why not use a mobo header and regular pc fans (which would allow you to read fan speed and control the fan speed from software)?

[oskupc]

9 hours ago, Biohazard777 said:

Well 1st of all, the link leads to ebay search (not a specific product).

I'll break up the response in two parts:

 

1) Physical connection

I'm gonna use the 1st search result (for me): https://www.ebay.com/itm/255662305595

 

Pay attention to the connector:

Sadly the description doesn't say what kind of connector that is:

2-pin, yeah no shit...

That is a very small 2pin connector, if you want to use that connector with regular fan connectors found in a PC:

You will quickly notice the fit isn't right (the pitch is probably gonna be too small on the male side), it is too shallow, and the "lock" doesn't align (even if you could jam it in there it won't be secure).
So you'd either have to get another adapter for that as well or cut the cables and splice the wires manually.

------

( I'm intentionally not gonna name all the possible connector types, makes this conversation harder to follow and you can pretty much visually spot when something isn't gonna fit )

------

Or.. you could buy a 3 pin fan with a "normal" connector:
https://www.ebay.com/itm/142673032310

As and added bonus this one will report speed (thanks to the 3rd signal/tach wire). More about that in part #2.

 

Anyhow even if you mess up and order with the fan with the wrong connector it won't be the end of the world, you can always cut the wires and splice them manually.

2) Wiring
You can use a molex to 3 pin or 4 pin fan adapter (doesn't matter, I explain why further bellow), and a 12V fan.
Because molex carries 12V (it also carries 5V but that is irrelevant for your use-case):

If you try it with 24V fan it either will not spin up at all, or if it does it would run slow... so do not buy a 24V fan.

 

As for pins, 2 pin fan means it only has + and -. These fans do not report how fast they are spinning, the only way to control their speed is by changing voltage.
3 pin fan means it has +, -,  and sense (aka tach / tachometric signal) wire, that wire reports back how fast the fan is spinning. These fans are also voltage controlled.
4 pin fan means it has +, -, sense, and PWM control (signal wire that tells the fan to turn on/off very quickly, thus controlling speed).

 

So that is why it doesn't matter if you use a molex to 3 pin or 4 pin fan adapter.
You will not be using PWM to control their speed, nor do you have a tach wire to read the actual speed of the fan.

2-pin 12V fan will constantly work at fixed voltage of 12V provided by molex.

 

May I ask what do you want to cool with those fans?
Why not use a mobo header and regular pc fans (which would allow you to read fan speed and control the fan speed from software)?

For this

Spoiler

 

 

I didn't know 3-pin 40mm fan existed, i will go for this.

The wiring information is also helpful, never thought about it before.

Thank you.

[Biohazard777]

1 hour ago, oskupc said:

For this

  Hide contents

 

Ah I see, custom/3D printed rear exhaust, cool.

 

1 hour ago, oskupc said:

Thank you.

You are welcome.