I'm trying to get 9V for my Arctic Fan 3 using a resistor. It's rated for 0.16A @12V.
I just started learning about circuits and stuff, so I tried some calculations. I assumed that the fan was a resistor (not an inductor, since I haven't learned that yet). I used the specs for Zalman's ZM-F1 fan since it included a 56ohm resistor (http://www.zalman.co.kr/eng/product/vie ... 0&code=016). I got similar results, so I applied this method to a 0.16A fan, which yielded a 25ohm resistor.
To people with some background in circuits, is 25ohms a good estimate?
Fan resistor
Moderators: NeilBlanchard, Ralf Hutter, sthayashi, Lawrence Lee
Fans are tricky beasts, as the effective resistance will change as the speed changes.
You would be better off using diodes to get the drops in voltage you want. Have a look at the site below and it will tell you all you need to know.
http://www.cpemma.co.uk/diodes.html
The advantage of using diodes is that the voltage drop is always the same, so if you change your fan you can still use the same diodes to get the same drop in voltage. As you have found out with your calculations, different fans need different resistors for the same voltage as the current drawn affects the voltage drop through the resistor.
The site has a controller called a Diobus listed on it that looks complicated but is pretty simple yet very useful for altering the voltage you supply to your fans. Someone also made a simpler version on this forum too but I forget who. A search for 'diobus' on the forum should yield the thread.
BTW - I didn't bother to check you calculations, so I'm not saying you're wrong. Just suggesting a possible alternative.
Have fun with your modding...
You would be better off using diodes to get the drops in voltage you want. Have a look at the site below and it will tell you all you need to know.
http://www.cpemma.co.uk/diodes.html
The advantage of using diodes is that the voltage drop is always the same, so if you change your fan you can still use the same diodes to get the same drop in voltage. As you have found out with your calculations, different fans need different resistors for the same voltage as the current drawn affects the voltage drop through the resistor.
The site has a controller called a Diobus listed on it that looks complicated but is pretty simple yet very useful for altering the voltage you supply to your fans. Someone also made a simpler version on this forum too but I forget who. A search for 'diobus' on the forum should yield the thread.
BTW - I didn't bother to check you calculations, so I'm not saying you're wrong. Just suggesting a possible alternative.
Have fun with your modding...