[Solved] Adding LEDs directly to case fan's wires.

[BuBu Shofronea]

I'm not so good at this stuff but i was wondering i would add some 12v LEDs ( i choosed 12v becasue the fan is also 12v... ) directly to the wires of the fan, like + to + and - to -, will they work - i mean will they not burn ?

I want to add them to a 4-pin PWM fan.

Btw, will they make the fan spin slower ? I'd like to add 4 of them...

 

[nukemaster]

LED's will have no effect on the fan as they are parallel with it(in series they would drop so much voltage and may even burn under the load(20ma is tops for normal leds, but some can take much more) of trying to start a fan, but I have never tried such things.).

This should give you an idea. The resistor depends on the led forward voltage.

Note: not all fans use the same colors so always check the position in the plug.

All the LEDs are parallel to the fan and each set of 2 is in series with one another and the 2 sets are in parallel with each other.

 

[BuBu Shofronea]

LED's will have no effect on the fan as they are parallel with it(in series they would drop so much voltage and may even burn under the load(20ma is tops for normal leds, but some can take much more) of trying to start a fan, but I have never tried such things.).

This should give you an idea. The resistor depends on the led forward voltage.

All the LEDs are parallel to the fan and each set of 2 is in series with one another and the 2 sets are in parallel with each other.

Gush, this really gives me headaches. Could you also please, tell me, based on your circuit, and on 5V LEDs, what resistors should i buy ? But on 12V ?

 

[nukemaster]

If you buy "5 volt" leds they already have a resistor installed in the wire.

I do not know what resistor value these 5 volt leds have to begin with. This makes it hard to tell what you will need. If they are 3.2 for forward and the resistor on them is for 20 milliamps, i would be about 100 ohms. Now with 2 of them in series(so 200 ohms already in the circuit) along with a 120-150 ohm resistor(you could add this) you would get maybe 17-18 milliamps across them from 12 volts.

It would be best to read up on led's to understand exactly what you are doing with them. Also where did you get these leds?

 

[BuBu Shofronea]

If you buy "5 volt" leds they already have a resistor installed in the wire.

I do not know what resistor value these 5 volt leds have to begin with. This makes it hard to tell what you will need. If they are 3.2 for forward and the resistor on them is for 20 milliamps, i would be about 100 ohms. Now with 2 of them in series(so 200 ohms already in the circuit) along with a 120-150 ohm resistor(you could add this) you would get maybe 17-18 milliamps across them from 12 volts.

It would be best to read up on led's to understand exactly what you are doing with them. Also where did you get these leds?

Man, i didn't even buy them yet, so that's why i want to clarify it now. I made something easier for my dumb brain and please tell me if it's correct : http://postimg.org/image/dzd1t2vnt/e84a0575/

I can't figure it out in any other way than this by your circuit, so if there's anything wrong ( or even the whole circuit ), i beg you to remake it, but in the exactly way i have to do it with the fan. Thx. in advance.

If i buy a higher resistor, like 1k Ohm, will i get rid of all these calculations ? I mean i just want them light for gods sake X.X

 

[BuBu Shofronea]

Forget about the image above, look on this one please, it's exactly made by your circuit : http://postimg.org/image/wbryzl5e7/15243645/

 

[BuBu Shofronea]

Btw, is this procedure good ? : http://www.instructables.com/id/Add-LCDs-To-Your-Computer-Fans/?ALLSTEPS

 

[nukemaster]

The second image and the link to .instructables.com look fine.

Not all fans have LED holes, but many do in fact have them, you may need to drill them out in some cases.

I will get you some images of an led fan from Antec so you can see exactly what they do.

Using a 1k resistor will result in dimmer leds(may 5-6 ma per led. For white/blue and some green this is still a good bit of light.)

EDIT. The antec fan has its resistors on the fan board so that would just be confusing.

 

[BuBu Shofronea]

The second image and the link to .instructables.com look fine.

Not all fans have LED holes, but many do in fact have them, you may need to drill them out in some cases.

I will get you some images of an led fan from Antec so you can see exactly what they do.

Using a 1k resistor will result in dimmer leds(may 5-6 ma per led. For white/blue and some green this is still a good bit of light.)

EDIT. The antec fan has its resistors on the fan board so that would just be confusing.

Thx. One more question. As i solved the circuit part, only the resistors would be the problem. I applied the Ohm law ( V = I x R ) and, as i use a resistor for 2 leds, i ended up with 696Ohm resistor. I have no clue if that's right but coul you aproximate, by all the data i gave you till now, what resistors should i get ?

And one more thing : does the led voltage ( liek 5v or 12v leds ) influence the resistor's ohm value ?

And another more thing 😀 : what do you recommend me : 12V or 5V LEDs ?

 

[nukemaster]

12 and 5 volt leds are just normal leds with a resistor installed on one of the leds or wires. They may be more bulky.

I think your ohms law is a bit off.

All diodes including those that emit light have a voltage drop. This drop in voltage has to be taken into consideration when running leds.

Lets use ledcalcs numbers
Red and green: 2 volts
Blue and white: 3.0 - 3.5 volts
Now some green leds will be 3.0+ volts. This should be on the specs.

If you are just getting into this getting a breadboard is a good idea since you can test things before installing them.

Moving on to resistor values.

Voltage - Forward = voltage the resistor needs to drop at a certain current.

So lets say you have 12 volts and want to run 2 x 3.2 volt leds

12 - 3.2 - 3.2 = 5.6

Now 5.6 / current in amps(I will use 17 milliamps)

5.6/0.017 = 329.4117647058824 with the nearest at 330ohms

LEDcalc.com does all this for you(no math needed, but math never hurts you).

Forward voltage is important for getting the right resistor value. It also changes with current for this reason, I tend to over-estimate a bit and run lower current. If you want to MAX it out you will need to test with the leds you want to use.

Here are the forward voltages of some leds i had laying around here(yeah yeah my meter is connected backwards, but it still works). Do not worry about other stuff on the breadboard because it is a current source so no matter the forward voltage the set current will always flow.

@ 12 mA

@ 18mA You will notice the white now has a higher forward voltage. The others moved up a bit as well

Please remember you do NOT have to connect the leds to the fans own cable, you can use an old Y cable/molex directly from the power supply instead.

 

[BuBu Shofronea]

12 and 5 volt leds are just normal leds with a resistor installed on one of the leds or wires. They may be more bulky.

I think your ohms law is a bit off.

All diodes including those that emit light have a voltage drop. This drop in voltage has to be taken into consideration when running leds.

Lets use ledcalcs numbers
Red and green: 2 volts
Blue and white: 3.0 - 3.5 volts
Now some green leds will be 3.0+ volts. This should be on the specs.

If you are just getting into this getting a breadboard is a good idea since you can test things before installing them.

Moving on to resistor values.

Voltage - Forward = voltage the resistor needs to drop at a certain current.

So lets say you have 12 volts and want to run 2 x 3.2 volt leds

12 - 3.2 - 3.2 = 5.6

Now 5.6 / current in amps(I will use 17 milliamps)

5.6/0.017 = 329.4117647058824 with the nearest at 330ohms

LEDcalc.com does all this for you(no math needed, but math never hurts you).

Forward voltage is important for getting the right resistor value. It also changes with current for this reason, I tend to over-estimate a bit and run lower current. If you want to MAX it out you will need to test with the leds you want to use.

Here are the forward voltages of some leds i had laying around here(yeah yeah my meter is connected backwards, but it still works). Do not worry about other stuff on the breadboard because it is a current source so no matter the forward voltage the set current will always flow.

@ 12 mA

@ 18mA You will notice the white now has a higher forward voltage. The others moved up a bit as well

Please remember you do NOT have to connect the leds to the fans own cable, you can use an old Y cable/molex directly from the power supply instead.

Wow, that's some serious stuff, but unfortunately, i just don't think i needed all of these stuff. Thx for all, but i still didn't get what i asked for.
I decided to choose blue which has that voltage forward or whatever it is from 3.0 to 3.5, so let's take 3.3. According to that value, i'll double it cuz i'll use 2 leds for one resistor, 2 same leds. From here i wanted you to tell me, by all these mathematics procedures, what;s the nearest resistor i should get.

And you said that either i take 12V leds or 5v leds, the resistor would remain the same, right ?

Thx. in advance.

 

[nukemaster]

Safest bet is to get some 330 ohm resistors. Should cover any led from about 2.8(right on the edge) to 3.5(a bit dimmer, but should still be bright enough) volt forward in a pair.

As said above the 12 and 5 volt leds already have a resistor on them. If you get 12 volt ones, you do not use a resistor, but you also connect them all in parallel.

So
Positive -> "12v LED" -> Negative
Positive -> "12v LED" -> Negative
Positive -> "12v LED" -> Negative
Positive -> "12v LED" -> Negative

The 5 volt ones would most likely need something like a 120-150 ohm resistor with 2 of them in series.

So.
Positive-> resistor(120-150ohm) - > 5V LED -> 5V LED -> Negative
Positive-> resistor(120-150ohm) - > 5V LED -> 5V LED -> Negative

Please send a link to the leds you are getting it may help. Sometimes leds are sold without resistors inline and those will not live without a resistor in line.

 

[BuBu Shofronea]

Safest bet is to get some 330 ohm resistors. Should cover any led from about 2.8(right on the edge) to 3.5(a bit dimmer, but should still be bright enough) volt forward in a pair.

As said above the 12 and 5 volt leds already have a resistor on them. If you get 12 volt ones, you do not use a resistor, but you also connect them all in parallel.

So
Positive -> "12v LED" -> Negative
Positive -> "12v LED" -> Negative
Positive -> "12v LED" -> Negative
Positive -> "12v LED" -> Negative

The 5 volt ones would most likely need something like a 120-150 ohm resistor with 2 of them in series.

So.
Positive-> resistor(120-150ohm) - > 5V LED -> 5V LED -> Negative
Positive-> resistor(120-150ohm) - > 5V LED -> 5V LED -> Negative

Please send a link to the leds you are getting it may help. Sometimes leds are sold without resistors inline and those will not live without a resistor in line.

Well, i'm buying them from a local shop 😀

Thx. alot for your support, but there's still a missunderstanding : i tought that 12v and 5v leds will require the same resistor, you said here that for a 5v i should get 120/150Ohm resistor and for the 12v a 330 one.

If so :
5mm 5V Blue LED - 120/150Ohm Resistor
5mm 12V Blue LED - 330Ohm Resistor

So those are the answers, right ?

EDIT : Reading your post again, i understood that, using my/your parallel circuit, getting a 12V LED won't need also an resistor, only the 5V will do or what?

 

[nukemaster]

Yes buying "12v" leds will not need any resistors because they should have them inline. You should also have no problems seeing them since most of the time they are under shrink.

5 volt ones would need resistors, but if you can get 12 why use the other ones. If you get bare leds with no resistor then a resistor is needed for sure. Almost no way around it, if you do not have low enough voltage and low current you can get by without one. This is why watch battery flashlights do not tend to use a resistor(they lack the current and voltage to need one).

So with "12v" leds you do something like this.

It does not matter where the led leads meet, they all go back to 12V and ground. If you used a molex connector you could access 5 volts, but you said you wanted to use the computers fan connector.

Pre wired leds may use different colors. Most likely it will be RED for 12v(or whatever voltage you want to use) and BLACK for negative.

 

[BuBu Shofronea]

Yes buying "12v" leds will not need any resistors because they should have them inline. You should also have no problems seeing them since most of the time they are under shrink.

5 volt ones would need resistors, but if you can get 12 why use the other ones. If you get bare leds with no resistor then a resistor is needed for sure. Almost no way around it, if you do not have low enough voltage and low current you can get by without one. This is why watch battery flashlights do not tend to use a resistor(they lack the current and voltage to need one).

So with "12v" leds you do something like this.

It does not matter where the led leads meet, they all go back to 12V and ground. If you used a molex connector you could access 5 volts, but you said you wanted to use the computers fan connector.

Pre wired leds may use different colors. Most likely it will be RED for 12v(or whatever voltage you want to use) and BLACK for negative.

Ok man, thank you very much. I think i got it.

And if i buy 5v LEDs, i'll use my circuit ( the one with resistors ). OK !
But is there any chance that 12V LEDs don't have inbuilt resistors ?

 

[nukemaster]

The only way a led can be sold as 12 volt is with a resistor built in(in the cable or in a housing with it most times.)

Higher powered LEDs can have higher voltage drop(forward voltage) because they are multiple leds in series(and parallel in some cases), but these are not what you are getting(as they are for lighting).

If you want 5 volt leds, get a molex(LP4) connector and just run them off the power supply.

 

[BuBu Shofronea]

The only way a led can be sold as 12 volt is with a resistor built in(in the cable or in a housing with it most times.)

Higher powered LEDs can have higher voltage drop(forward voltage) because they are multiple leds in series(and parallel in some cases), but these are not what you are getting(as they are for lighting).

If you want 5 volt leds, get a molex(LP4) connector and just run them off the power supply.

But one more thing : What were the values for the resistors to a 5V LED ? ( a resistor for 2x 5V LED ) ? ( sorry for keeping annoy you with that xD )

 

[nukemaster]

120 - 150 ohms this assumes 3.2 volt forward and 100 ohm resistors already integrated. This leaves about 320-350 ohms of total resistance(120-150 + 100 per led) with the 2 pre resistored leds.

If you happen to have a RadioShack or similar you can get a pack of random leds and also get a resistor value pack to allow testing different things out.

 

[BuBu Shofronea]

120 - 150 ohms this assumes 3.2 volt forward and 100 ohm resistors already integrated. This leaves about 320-350 ohms of total resistance(120-150 + 100 per led) with the 2 pre resistored leds.

If you happen to have a RadioShack or similar you can get a pack of random leds and also get a resistor value pack to allow testing different things out.

Ok, thx alot. ( but that integrated resistance is also found in this type of model of the 5mm 5V LED, right ? : https://www.google.ro/search?q=ima&safe=off&es_sm=122&source=lnms&tbm=isch&sa=X&ved=0CAcQ_AUoAWoVChMI9rf6pN_vxgIVSBYsCh32bABB&biw=1680&bih=881#safe=off&tbm=isch&q=5v+led&imgrc=Ft5xaTDWdK4izM%3A )

 

[nukemaster]

Yes, it is listed as such on the website

The Kingbright 5mm LEDs are a superb, high quality range of components incorporating an inbuilt series resistor enabling the LED to be directly connected to 5V or 12V supply lines.

They also list a MAX voltage of 6 for the 5 volt ones and 14 for the 12 volt ones.

 

[BuBu Shofronea]

So, before closing this thread, i suggest all of you who want to add LEDs to your fan, get 12V ones and follow the circuit of nuke ( http://i62.tinypic.com/wjxncz.jpg ). No resistors are needed as long as they are 12V.

Got some pictures with what i did by following that plan and it works like a charm :

Thanks man.

Thread closed.

 

[nukemaster]

Glad you got it all setup.

Well those look pretty bright.

Never thought I would see the Intel stock fan with leds like that.

I may put some green ones on a fan(not mine) at some point in the future(I have the leds/resistors anyway.).

 

[BuBu Shofronea]

"Never thought I would see the Intel stock fan with leds like that."

Was a pain in a$$ to fix them up there without a glue gun 😀

Oh, and i forgot to mention it did not take any power from the fan. Meaning its max speed it's the same as before 😉

 

[tech-wreck]

i used a red LED and a resistor (?ohms, trial and error until i found one that made the LED quite dim) in series, just spliced into the +ve wire so that the fan runs at 700rpm.
breadboards are useful for tinkering without worrying about calculations and stuff

 

[BuBu Shofronea]

i used a red LED and a resistor (?ohms, trial and error until i found one that made the LED quite dim) in series, just spliced into the +ve wire so that the fan runs at 700rpm.
breadboards are useful for tinkering without worrying about calculations and stuff

I used nukemaster 😀