Instructables

How To Make A Cheap USB Powered Fan

Step 4: Connecting the USB wires to the fan's battery terminals.

This was done through trial and error. I found that while the fan would run both if the red were attached to the positive and black negative or red to negative and black to positive but the second way produced sparks at the negative-to-motor connection so I obviously chose the former hook-up. Wrap the indicated wire around the indicated battery terminal folding the wire over so it stays temporarily. Once this is done, plug the USB wire into your computer (NOTE: Do this instructable at your own risk, I will not take the blame if harm comes to you computer/yourself/etc but nothing bad happened to me/my computer when I connected the fan to the computer) and turn the fan on. If it works, on to the next step, if not, maybe the wires are not connected properly or maybe they are loose, play around with it,m it should work fairly easily (and as long as the fan does not require 3 x 1.5V batteries or more for operation (IE no more than 5 V) ).
 
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nodoubtman2 years ago
I tried and the computer went off ... so don't try this, this motor needs a resistor, but how much Ohms??

Thank You!
CYa! :)
trebuchet038 years ago
Most (if not all) modern USB controllers have fail safe and short protection. I know on my computer if it find a short, windows has a popup saying that oh, BTW, you drew too much current and the hardware is now shut down... Typically a restart will turn the device back online... I noticed that knoppix did not tell me that the board shut down... I can't remember if fedora or Cent said anything... but in any case, the controller shut itself down.
I have a laptop that i took apart (took off the keyboard and stuff) and it was running while i was putting on the heat shield (not a smart thing to do) and it sparked a few times, big white and blue sparks, then it shut down. i dont know if that has a connection to that, but thats what happened.
From what I understand damage to the USB port and/or the device could result from overloading the voltage. I made a similar setup for a desktop fountain that ran on 2 "AA" batteries and used an LM317 adjustable regulator to drop the voltage from 5 to 3VDC. There are online calculators to figure out what resistances you need to run for a given output... Here's a link to some general info http://www.national.com/mpf/LM/LM317.html
TooShort47 years ago
Scared me to death. Did that but with a clock and it kept sparking until i unplugged it.