So, I'm looking to get into all this electric stuff, so I decided to make a small project.

I started with something "simple", so I took a regular 12V PC fan, got a USB cord, and put it all together. Red wire goes to red wire, black goes to black, etc. The fan works, but now I want to know if there are any issues that I could run into for doing this.

Issues like voltage differences. The fan is 12V, and a friend of mine said that my USB port only allowed 5V or something. Will this affect my PC? Will anything blow up?

Also, with that said, is there a way to control the speed of the fan with a program? Since its basically hot wired to the fan, and theres no microprocessor or anything of the sort, I don't think I can. But there might be a program to control how much power goes out, etc.

Anyways, sorry for the long post, I hope to get some good replies.

 

USB port will only output 5V. If the fan is turning, that means it must be running on 5V even if it's supposed to require 12V. Because it's a motor, it may be drawing more current than you would expect. The USB port is supposed to shut itself down if you try to draw too much current from it, but I have heard of damage resulting in rare cases. In particular, there will probably be current spikes when starting the motor, and these possibly could be more serious at 5V because the motor takes longer to start.

You would need a microcontroller to control the speed of the fan over the USB.

 

Might I suggest you find a 5VDC motor to use instead? Not only will you not have to worry so much about the above issues, but the fan will most likely sping a lot faster and be more effiecient. You can find a 12 volt fan in many computer surplus shops, or new ones at stores like http://www.mouser.com