Hi everyone, First time poster.

I am currently building a Laptop fan cooler and i wanted to run it from USB on my laptop with adjustable speed/voltage control.
It is housed in MDF.

I have not managed to find anything really with a diagram showing me how to make it. I'm a novice at electronics, but i know how to solder and such, just not the resistors/voltage changers/etc i would need to achieve it.

Essentially i want to change 5vv to 12 and then from that to the adjuster, then to the fans.. thing is i don't know how/what i'd need to build the circuit and need a diagram of how to put it together.

I've drawn up a picture of what i want to do so you guys can grasp the idea i have and possibly be able to provide help to my project :>

 

You can make a simple adjustable power supply with an LM317..

 

You can make a simple adjustable power supply with an LM317..

Use PWM to control speed.

 

Use PWM to control speed.

from the few times I tried it with typical modern computer fans they don't like PWM.. It messed up the internal sensors.. and they just won't start/stall/hum..
But others work just fine with it.
I've found with 12V fans that you can usually go down to about 5V and get all the needed speed control without having to resort to PWM.

 

from the few times I tried it with typical modern computer fans they don't like PWM.. It messed up the internal sensors.. and they just won't start/stall/hum..
But others work just fine with it.
I've found with 12V fans that you can usually go down to about 5V and get all the needed speed control without having to resort to PWM.

Yeah, but how would i go about wiring it up? If you would'nt mind drawing it on the diagram i posted i'd be greatful. It's just helps me know where to position/wire up the LM317. And i use 3 pin or molex Fans.

Thanks!

 

Oops.. missed the USB part for some reason.. That will require a step up DC/DC converter to go from 5V to 12V.. I'd think you could find an adjustable output one and then there is no need for the LM317.. For some reason I thought you might have a 12V power supply already when I wrote that.

And you need to post the specs on the fan... we know 12V but how much current.. USB is really limited in how much current it can deliver anyways.

 

Try to use 5V fans. That will make life a lot simpler.

 

Try to use 5V fans. That will make life a lot simpler.

That would be WaaaaaaaaaaaY too easy.

 

I have a laptop cooler. Its two fans have no speed control. You'll probably find you would run yours at full speed all the time .

 

I have a laptop cooler. Its two fans have no speed control. You'll probably find you would run yours at full speed all the time .

Same, got mine from Big Lots for 6 USD and tax.

 

You really don't want to run the fans from the laptop computer's USB port; as there's only about 300mA available to begin with, which will be severely taxed when stepping up to 12v to run fans. Use a "wall wart" 12v adapter; they're available everywhere - you and/or your neighbors probably have several of them sitting around doing nothing.

 

You really don't want to run the fans from the laptop computer's USB port; as there's only about 300mA available to begin with, which will be severely taxed when stepping up to 12v to run fans. Use a "wall wart" 12v adapter; they're available everywhere - you and/or your neighbors probably have several of them sitting around doing nothing.

Oops.. missed the USB part for some reason.. That will require a step up DC/DC converter to go from 5V to 12V.. I'd think you could find an adjustable output one and then there is no need for the LM317.. For some reason I thought you might have a 12V power supply already when I wrote that.

And you need to post the specs on the fan... we know 12V but how much current.. USB is really limited in how much current it can deliver anyways.

Well, i'm not always at the wall sockets, so i suppose a pair of 5v fas would work. But i want to control the speed, which is why theres a potentionmeter in the circuit.

So what do you reckon i should use then to convert it? I don't know how to build a 5v - 12v converter, let alone where to put them in that circit. And i guess the fans would be 0.4A?

 

If the fans take 0.4A x 2 = 0.8A at 12V they will take 1.92A at 5V with no conversion loss, so many 2.2A. This is a non-starter. You USB port cannot deliver that power.

Maybe you should consider getting a newer laptop, they run very cool and can go 9 or more hours on a charge.

Bob

 

Just try running 12 volt fans from USB (5 volts), see if they run, see if they run well enough.

I have a few 12 volt pc fans, they are generally 0.1-0.15 A, so they should work ok with the amount of current that USB is able to provide.

 

If the fans take 0.4A x 2 = 0.8A at 12V they will take 1.92A at 5V with no conversion loss, so many 2.2A. This is a non-starter. You USB port cannot deliver that power.

Maybe you should consider getting a newer laptop, they run very cool and can go 9 or more hours on a charge.

Bob

They are guessing that fans are 0.4 A. I would not trust that guess.

 

Just try running 12 volt fans from USB (5 volts), see if they run, see if they run well enough.

I have a few 12 volt pc fans, they are generally 0.1-0.15 A, so they should work ok with the amount of current that USB is able to provide.

This can be used for speed control, but you might want to shop around for 555 chip, you will want one that takes 5 volts and can source 0.2 A or more: http://www.instructables.com/id/Simple-and-dirty-Pulse-Width-Modulation-PWM-Wi/

The fans are probably much less, they are just basic 12v case fans with no leds. 0.4a was just a guess. I don't have any fans to hand at the moment but i know i've ran them from a usb before at a fair decent speed.

They are standard 80mm fans. 150 - 500mA somewhere between these/

 

150mA * 2 = 300mA * 12 / 5 = 720mA, still out of spec for a USB port, with is a max of 500mA.

Bob

 

150mA * 2 = 300mA * 12 / 5 = 720mA, still out of spec for a USB port, with is a max of 500mA.

And 500mA is only allowed if the device is enumerated and request it. Without that, it is limited to 100mA.

You cannot make this work without an additional power supply or fans that draw much less current.

Bob

 

But i want to control the speed, which is why theres a potentionmeter in the circuit.

Buried in the discussion of how you are going to power the fans, it seems that your plan to modify the fans speed with a potentiometer has been lost.

This is not a good way to control the fans speed. The power rating of the pot will be high and finding a matching component at a reasonable cost will be difficult. Search the forum for PWM speed control circuits.