12V Sources?

I want to control my CPU fan thru use of Arduino Uno however it's rating for 12v 0.35A. Since Arduino can only handle 5v I need to find a 12v source. However I can't think of many 12v batteries unless it is a tractor battery or larger. I believe the solution to my problem is finding a mosfet to bump up my voltage from 5v -> 12v. Am I on the right track?

Yes, thats right. Make sure it is a "logic level" fet and rated for around twice the current the fan will draw. A bjt transistor would also be fine, eg. Bc337.

Post a scematic (hand drawn is fine) and we will check it for you.

Paul

No, MOSFET alone was not able to bump up the voltage from 5v -> 12v.
You need the DC DC step up converter like this
!(http://i.ebayimg.com/t/LM2577-DC-DC-Converter-3-34V-to-4-35V-15W-Step-up-Power-Supply-Boost-Module-/00/s/NzM3WDczNw==/$(KGrHqNHJBME-eKWlp,ZBPzC!0MK,g~~60_35.JPG)
eBay

Ah, I see now. Ok the LM7812C mosfet will step down the voltage from 19v → 12v. But I’m looking to raise the voltage from 5v. i will get the LM2577 DC DC Adjustable Step Up Power Converter Module. Thanks XD

Hi, if this is a 12V fan in a computer and it has been running in this computer then you already have a 12V supply. You don't need batteries or step up boards.
Use the FET to turn on the Fan, and have the Fan draw its supply from the existing computer supply, remember to connect arduino gnd to computer gnd.

Tom..... :slight_smile:

BillHo:
No, MOSFET alone was not able to bump up the voltage from 5v -> 12v.
You need the DC DC step up converter

Hi billho. Your suggestion is logically correct, but you should understand that beginners don't always ask the right questions. This project is meant to run inside a pc where 5V and 12V will be available. There is no need for a dc to dc step up convertor. The arduino will be able to run off 5V and a mosfet will be able to control the 12V to the fan.

Paul

encryptor:
Ok the LM7812C mosfet will step down the voltage from 19v -> 12v.

Hi encryptor, the lm7812 is not a mosfet. It is a voltage regulator. You do not need this beause you don't have a voltage suitable to run it inside a pc, and you don't need it anyway. You already have the 12V you need for the fan and the 5V for the arduino.

Paul

the hardware was only $3, so no big deal. I’m sure I’ll use it for other things to. Ok, a power supply already has the 12v and 5v supplies. i will have to check which connectors supply these voltages.