Do I need resistors to run a usb to this fan?
So I have a little project going, really simple. Just a computer fan that I will list the specs below and a usb 2.0 off of a iphone 4 cable.
I'm going to cut the phone charger to get the usb half and use the USB VVC +5v and the ground. I'm going to add a power switch as well. I have heard usb 2 chargers put out 500mA? The fan that I'm using only uses.08A at 12v. Do I need any type of resistors for this to not burn up the fan? I'm new to this so be kind. It seems as if the USB port will put out much more than the fan can handle.
Also if I'm just using the usb port for power and not data can I just cut the usb data+ and data- wires out of the equation? Also I want this to all be linear so could I just solder in some resistors into the circuit before the switch? What ohm resistor should I get?
Or if I'm going about this all wrong please tell me. This just seems like a simple circuit. USB to resistor to switch to fan back to usb ground.
Added (1). Update: If the usb only provides 5v and I need 12v could I use a transformer to raise the voltage? I know a usb 2 can power this tiny fan, the question is how can I do it efficiently.
No you don't need resistors.
Also, you should not use 5V to power a 12V fan. You can buy a 5V fan instead.
And, USB spec is 1/2 amp minimum. Many have up to 1 amp available.
If not in a hurry to receive the fan, there are 5V fans, and USB fans
http://www.miniinthebox.com/index.php?main_page=advanced_search_result&inc_subcat=1&search_in_description=0&keyword=5v+fan
http://www.miniinthebox.com/index.php?main_page=advanced_search_result&inc_subcat=1&search_in_description=0&keyword=usb+fan
No idea why you would try to force a 12V fan to run at 5V. In any case, no resistors are needed.
You need to convert the 5V to 12V.
Thanks all to answer my question… I relay help full…
You're hacking an old phone charger for your power supply? You should not need a resistor at all. The fan will draw only the current it needs.
But you're using a 5 Volt supply to run a 12 Volt fan. That's not necessarily a problem: many computer fans rated for 12 Volts will run at a reduced speed if you use a 5 Volt supply. (That's just what many fan speed controllers do.)
I think it will work just fine. Go for it. No resistors.
You shouldn't really need a resistor to limit your current. But if you want to add one, use a 10 ohm 1/2watt or 1 watt in series
edit: oh that's a 12 volt fan? Yeah. Not sure that 5v will even cause it to spin… And don't try putting 2 usb cables in series…
about about using a 9v battery or two 9 volts in series with about a 500 ohm resistor. (that value is a guess. My ohms law is rusty
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