Hello guys!
I've little knowledge about electronics so I'm asking for your help .
I've build a cooling pad for my laptop using 2 80mm fans with 5v 0.3 A as specs, they are simply wired in parallel to a usb cable.
Now i have 2 questions, the fan's speed is constant when i plug to a usb wall charger (2A) and when i plug to the laptop's usb2 ports so i'm assuming the laptop's usb output is sufficient, is it risky to use the usb port with this specs?
The second question is about the speed of the fans, they're loud and i would like to regulate manually the rpm with some kind of potentiometer, i found some cheap control boards online but i'm not really sure on what i really need to buy, is a "1.8V 3V 5V 6V 12V 2A Low Voltage Motor Speed Controller PWM 1803B" okay? I need something else to protect the usb port?

Thank you for your help!

 

The USB port is pretty well protected so you don't need to worry about it.
From the brief description given it sounds like that controller would do the job.

 

Thank you for the reply, I'm worried because i read some posts about burning the motherboard using recklessy the usb ports. . .
Anyway I'm attaching the photos of the components

 

I was just a little concerned that the description of the speed controller says it '...controls the direction...'. This would mean reversing the polarity of the voltage to the motor. This would likely damage your fan motor. However, I found the same product available on Amazon and the description there only speaks of controlling the speed so I think it is just a matter of poor translation, and so this controller will do the job nicely.