DIY Fan LED Mod
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What You Need and Theory
Here's a quick guide to making your own LED fan. As always, this is a guide only - perform this mod at your own risk. You'll need:
Soldering iron, 20-40w or so
Drill with 4.5mm bit
About 15cm of heat shrink
4 LEDs of your choosing (1000mcd or more)
About 35cm of hook up wire
First off: power
I decided to take power directly from the fans own power leads. This would reduce me having to have even more wires flapping around my case. in the photo below you can see the resistor coming off the red wire and connecting to the LED and a red wire going off to the right under the electrical tape, that is the negative end of the circuit.
Now, what value resistor?
Well, each of the LEDs I used (DSE cat. Z-4072) have a max continuous forward current of 40mA, and a voltage drop of 1.8v. since there are 4 LEDs i can wire them in series and have a voltage of 7.2v across them. This leaves 4.8v to be dropped by a resistor with about 40mA going through it. To be safe lets calculate it for 30mA, just so the LEDs a bit more in spec.
Now, using ohm's law:
For the wattage:
A 1/4 watt resistor will be fine. So, a 160 ohm resistor will do nicely. I used 120 ohm and have 40mA which should be ok and will produce slightly more light, but use 160 if you want to be sure not to blow your LEDs.
For resistor values with LEDs with other voltages here is a quick guide:
Voltage drop = 12v - total of LEDs in series
|Voltage Drop||Current||Resistor (ohms)|
If you decide to use 3.5v LEDs 2 resistors will be needed and the LEDs will have to be wired as 2 groups of 2 in series with a 5v drop.
All original content copyright James Rolfe.
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