Resistors undervolting fans...HELP!

[chynkboi]

I have some 1/4W +/- 5% 33k OHMS resistors and I tried putting them on the positive wire of the fan to make it undervolt and go slower but its not working out. Any info or tips why its not working? Any suggestions?

I'm pretty lost because I just did a little research and thought this would work....

 

[Evadman]

You put a 33,000 ohm resister(s) in series? I am dumbfounded. where in the world did you read to do that? That means the fan is getting like 1/10,000th of a volt instead of 12. 7-9v is where you want to be if you are trying to slow it down.

 

[chynkboi]

what do you suggest?

 

[Moohooya]

Don't use a resistor. The resistor will just put out heat, hence no gain.

You have several solutions. Hook up the fan to different lines. Remember you do not need to use ground. People sometimes use +5 and +12 to give a 7v difference.
Use PWM to vary the fan speed. I tried this with little success as I tried to vary the pulse width.
Use a variable voltage regulator. This should be a switching type to avoid it acting as a resistor. (See line 1)

 

[JSSheridan]

DC power concepts take some effort to learn. If you give us the rated power of your fan and it's supply voltage (could assume 12v but you never know) we can tell you. Peace.

 

[chynkboi]

actually, i'm doing this for 3 pin fans that u can not do the 5v or 7v trick on. so, what do you recommend.. how many OHMS?

 

[chynkboi]

yea, i need one that sucks about 6v (half) of it away

 

[JSSheridan]

Dropping the fan's voltage to 6 V will take 75% of it's power. If you want to take half of the fan's power away, you'll want to give it around 8.5 V. The relationship between voltage and power isn't linear. Power equals voltage squared multiplied by the resistance, P=V^2*R. By the way, what's the power rating of the fan? Peace.

 

[chynkboi]

so, you still did not suggest a OHM amount.. want to tell me or is it too complecated for ya?

 

[JSSheridan]

Without knowing what the power rating of the fan is, I'd just be guessing. Just guessing then, I'd say 5 to 8 ohm, rated for 1 watt. Peace.

 

[Bleep]

want to tell me or is it too complecated for ya

Sounds a little ungratefull to me. You see it involves ohms law where you have to know 2 of the parameters before you can figure out the 3rd.
If you are to lazy to post the fan parameters you are not deserving of a answer.

Bleep

 

[JSSheridan]

Originally posted by: Bleep
Sounds a little ungratefull to me. You see it involves ohms law where you have to know 2 of the parameters before you can figure out the 3rd.
If you are to lazy to post the fan parameters you are not deserving of a answer.

Bleep

Now Bleep, let's not be hasty now. The last thing I want to see happen in the GH forum is a little war break out. It was probably not meant to be taken seriously anyway. Be cool guys. Peace.