Tutorial: Adding multiple LEDs to a basic case fan.

Im planning on doing this with 16 red LEDs, would I still need to use a 100ohm resistor for each string of 4 LEDs?

Also, is there anyway you could explain the 'Wiring up the common Positive and Ground wires' bit a little more? Id be really grateful
Im not good with electricity you see.
Thanks
 
I'd probably go for 150 ohm resistors for a Red LED circuit. I think Reds have a forward voltage of 1.9v or so, where my Oranges were up to 2.2v

Check the spec of your chosen LEDs

The common positive and ground is a part of the guide which I had some trouble describing, which wasn't helped by the fact that I didn't take that many photos of that part if the build.

Just think of the commons as two bits of wire that run almost all the way around the fan that provide 12v goodness to each string of 4 LEDs. The positive or red wire will join up the resistor side of each LED series but not touch any other parts. The ground or black wire will join up the negative side of the last LED on each side.

Having a single string of 16 LEDs just wouldn't work so we need to make 4 strings of 4.

There's a wiring diagram in post 2 with the wiring all laid out in a line.

Perhaps I need a fan shaped outline and have the wiring running around that as well. I did think of this but could only locate coloured images or 3D models of fans so didn't bother.

I'm thinking of modding a Noctua fan or two next.
 
Well doing the R=V/I it worked out as my LED's would need 111ohms as the ones im purchasing have a forward voltage/current of 1.8-2.0/18mA
Thats if I did the math right.


When you say join the red wire to each resistor, is that 4 different bits of wire, each one going from resistor to resistor, and then the same except with a black wire and the negative side of the last LEDs?

I hope you understand that :S
 
12v -2 -2 -2 -2 = 4v

Current = 0.018A

4 / 0.018 = 222 ohm. ?

The wizard I use gives me 270ohm but I'd come down from that to get better brightness.

You have sourced ultra bright LEDs haven't you? 20mA seems to be customary for ultra heights and I usually go 25mA as they have max if 30mA.


On my iPod so don't have a good way to calculate.

Yes that can be different wires if you wish but you could also bare a section in the insulation, what we used to call a window strip. Tricky to do but neat. You can hook the resistor leg around the window strip and solder in place. Or run 3 bits around all joined together. You don't want to join it back up and form a loop, that would be bad.
 
Oh right, I did 2.0 / 0.018
Thanks for clearing the ohm's up for me

Yeah, the description on the Bay says they are Super Bright.


I think I might do 3 separate bits of wire, as it will be easier for me. Do I need to solder it may I ask?

And sorry about all these questions, but is there anyway you would be able to explain how to wire it to the single molex already on the fan? As I dont have a spare one to use. If you cant, I will just buy a cheap fan for like £2 an remove the molex off that.

Thanks for the help by the way.
 
Maybe you could copy and paste the spec for me?

You will need to solder. Irons arte cheap as chips on the bay and I'd imagine so is solder. Do some practise solders first. Remember also to tin all legs for best results.

Are we talking Molex or Fan connector? Anyway what I would do is to cut the wires somewhere on the fan's own wires and join in my own wires to form a sort of Y joint. Best place would be close to the fan itself I'd imagine, with less wiring to hide it would be neater. Cover the exposed wires with heatshrink or insulation tape.
 
Description
Red color
Size 3mm (Diameter)
Water Clear Lens
Forward voltage / current : 1.8v - 2.0v, 18mA
Wavelength (nm) : 620 - 625 - 630
View angle : 25 degrees
Luminous intensity : 4000mcd


Yeah, I have found a solder iron for a tenner in a high-street store and they have a bit of solder in there too.

I mean, you know how you wired another molex power connector to power the LEDs separate to wiring it into the standard fan.
I think I will just use a second molex connetor though, as it seems so much easier.
 
I'd go with 200 ohm then. This will drive them to about 22mA which will be fine. 150 ohms would drive them up to 27 mA which might be bad for them.

I'm sure you must have some spare Molex -Molex to fan converter like I have imaged in Post 1 (Image 4).

Just cut the fan connector off (leave a few inches of wire for a possible future use) and join to your LED common wiring.

Make sure you post some pics of your end result.

If you have any more questions feel free.
 
Tealc said:
I'd go with 200 ohm then. This will drive them to about 22mA which will be fine. 150 ohms would drive them up to 27 mA which might be bad for them.

I'm sure you must have some spare Molex -Molex to fan converter like I have imaged in Post 1 (Image 4).

Just cut the fan connector off (leave a few inches of wire for a possible future use) and join to your LED common wiring.

Make sure you post some pics of your end result.

If you have any more questions feel free.
Click to expand...

I will try and get my hands on some 200ohm ones.

Well I have only ever done this one build, and other than the 3 fans which came with my case, I bought one other fan (which happens to be a Xilence Red Wing 120mm). It has two connections, a 3pin which I plug into the mobo and a 4 pin molex connector.

I still need to get all the tools and parts, and I wont be attempting it for 2-3 weeks (I have a holiday planned) but I will be sure to post pictures of the outcome.

My final question is with the red and black wires that I connect to the LEDs and the resistors, do they connect to the red and black wires on the molex?

Thanks so much, and sorry if I am a pain.

Thanks a lot for the help.
 
The Yellow and Black wires in a 4 pin Molex are +12v and Ground, so you could wire to those pins. The Red and Black wires heading to a fan connector are also +12v and Ground.

You don't want to connect to the 5v line on the Molex so just watch for that.

molex-fan-connector.jpg
 
Im back with some more queries as I have decided to do green LEDs instead (after watching the Matrix Trilogy on ITV2 :P)

I think I have it right but would like some checks from yourself before I purchase my LEDs etc.

The LEDs I have chose have specs as follows:
Green color
Size 3mm (Diameter)
Water Clear Lens
Forward voltage / current : 3.2v - 3.6v, 20mA
Wavelength (nm) : 520 - 523 - 526
View angle : 25 degrees
Luminous intensity : 15000mcd

Using a voltage of 3.4 I worked out I could have 12 LEDs, 3 in each string, and use resistors of 43ohms (it calculated as 90 but I lowered it to make them a little brighter).

I hope im not being a pain. Thanks
 
15000mcd? I think that seller might be inflating that figure somewhat. That resistance should be ok I'd imagine.

The first fan I modded was done with 12 LEDs. It looks great but I did find that the middle LED sticks out of the fan a little more and prevented me fitting in the rear fan spot on my case. My second fan was a lot neater though and may have fitted. I haven't even installed the one from this tutorial yet.

Good luck with the Mod. Green is a cool colour for a fan.
 
I think it must be a typo because the seller has other red LEDs for sale with 4 and 5 thousand mcd.

Well my rear fan has red LEDs which I will be changing to green, so the fan I add 12 LEDs to will be put on the side.

Thanks so much. Red and blue seem to be rather popular and I would like something different, another reason why I decided on green :)
 
For the molex I use to power the LEDs, do I literally rip it off the fan (the spare fan I have not the one im modding)? So it bares the wiring inside the insulation and then solder to that?
 
You can use any Molex, provided it has the two wires you need.

Here's a selection of options.

Molex to Fan cable.

Molex to PCI-E cable.

Molex to Sata cable.

You don't need to destroy a fan to do this mod.

You must have some spare cables from your PSU, Motherboard, drives?
 
What exactly do you mean by Molex to Fan, Molex to PCI-E, etc.?

Do you mean like adapters?
Because I literally dont have any.

EDIT

I have some spare fans from another ancient computer which I can remove the molex from.

I bet you'll be glad when I finally do it, all this hassle, ha.
 
Last edited:
As long as you didn't intend using them again then it's all good.

I just want to see the end result in green, or whatever colour you decide to do.. :D
 
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