Foundry edgeiron 4802cf - quiet down.

[shovenose]

Well, it has three little fans and they are really annoying. The unit does not get so warm. Will I need a resistor and which kind?
Thanks.
Also why when I put it in Full Duplex the activity indicators don't blink. How do I set it to still show me activity?

[mariushm]

Re: Foundry edgeiron 4802cf - quiet down.

Find out what voltage the fans run at and what current they need for full speed. It should say on the label.

Let's say the label shows 12v , 0.25A

V = I x R (ohm's law) ... hence I = V/R or R = V/I

So R = 12/0.25 = 48 ohm ... that's the load of the fan

If you want to reduce the voltage appearing on the fan, you need to drop some of it on a resistor.

Let's say you want to drop the voltage to 7v , that means 5v have to be dropped on the resistor.

The fan's new current will be .. V = I x R => I = V/R = 7/48= 0.145 A.. just to make it easy let's say 0.15A.

So now the resistor has to allow at least 0.15a through, to the fan, and drop 5v on it:

V= I x R , R = V/I => R = 5v / 0.15 = 33 ohm

Power dissipated in resistor is computed with formula P = I^2 x R

So P = 0.15x0.15x33 = 0.74 watts.

So you'll need a 33 ohm 1 watt resistor (or higher, a 2w resistor will stay cooler)

Now this math is just for one fan, and to slow it down to 7v... if you have all three fans in parallel, add the currents before doing the math.
And I'd suggest lowering their voltage just to about 9v, maybe they'll be silent enough.

[shovenose]

Re: Foundry edgeiron 4802cf - quiet down.

I'll check tonight and post here, thanks!