Tutorial: Adding multiple LEDs to a basic case fan.
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If you go for 8 on a single 80cm fan you'll have a few choices.
1) 2 sets of 4 LEDs per string.
+ve ------LED------LED-------LED-------LED------ -ve
Each LED would share the 12v and receive 3v each. This may not be desireable as the LEDs I showed were...
..and may not achieve full brightness.
So you'd need..
2) 4 sets of 2 LEDs per string.
+ve ----resistor------LED------LED------ -ve
Now each LED is 3.5v typical, so that's 7v total string voltage needed. 12v - 7v = 5v to drop by resistor at 20mA which would require a 250 ohm resistor.
3) Or individually resistor each LED.
12v - 3.5v = 8.5v to dissipate at 20mA. 8.5/0.02 = 425 ohm or nearest standard value.
Or go for 12 LEDs per fan by having 4 strings of 3 LEDs each for the perfect solution given the parts you have purchased.
3.5v x 3 = 10.5v, leaving only 1.5v@20mA to dissipate by resistor. 1.5/0.02 is 75 ohm, so I dropped it to 56 ohm which was a nearby standard value.
And would end up looking something (but better than) like this (quick photoshop colour change)
With resistors you can combine them to make different resistances.
eg.
in series
--resistor---resistor--resistor--
has the effect of adding together. 56 + 56 + 56 = 168ohm.
or in parallel
_/--resistor--\____
..\--resistor--/
which just gets complicated.
1) 2 sets of 4 LEDs per string.
+ve ------LED------LED-------LED-------LED------ -ve
Each LED would share the 12v and receive 3v each. This may not be desireable as the LEDs I showed were...
..and may not achieve full brightness.
So you'd need..
2) 4 sets of 2 LEDs per string.
+ve ----resistor------LED------LED------ -ve
Now each LED is 3.5v typical, so that's 7v total string voltage needed. 12v - 7v = 5v to drop by resistor at 20mA which would require a 250 ohm resistor.
3) Or individually resistor each LED.
12v - 3.5v = 8.5v to dissipate at 20mA. 8.5/0.02 = 425 ohm or nearest standard value.
Or go for 12 LEDs per fan by having 4 strings of 3 LEDs each for the perfect solution given the parts you have purchased.
3.5v x 3 = 10.5v, leaving only 1.5v@20mA to dissipate by resistor. 1.5/0.02 is 75 ohm, so I dropped it to 56 ohm which was a nearby standard value.
And would end up looking something (but better than) like this (quick photoshop colour change)
With resistors you can combine them to make different resistances.
eg.
in series
--resistor---resistor--resistor--
has the effect of adding together. 56 + 56 + 56 = 168ohm.
or in parallel
_/--resistor--\____
..\--resistor--/
which just gets complicated.
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Sorry I'm trying to give you all the options.
If you are set on 8 LEDs per 80cm fan then you could combine 4 of your 56ohm resistors to make 224 ohm which is close enough to 250 ohm as laid out above.
You will need to have 4 circuits in total, each with two LEDs and a chain of resistors on it.
Please excuse the crudeity(sp) of this drawing.
So that would need 16 resistors and 8 LEDs per fan.
Or get some 240ohm resistors and keep the 56ohm for a future project and use just 4 per fan.
If you are set on 8 LEDs per 80cm fan then you could combine 4 of your 56ohm resistors to make 224 ohm which is close enough to 250 ohm as laid out above.
You will need to have 4 circuits in total, each with two LEDs and a chain of resistors on it.
Please excuse the crudeity(sp) of this drawing.
So that would need 16 resistors and 8 LEDs per fan.
Or get some 240ohm resistors and keep the 56ohm for a future project and use just 4 per fan.
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http://cgi.ebay.co.uk/10-x-240-Ohm-...al_Components_Supplies_ET&hash=item1c12903238
are they the one's i need tony ?
ill go with the more powerful resistors as the 80mm fan is not big enough to have to many items on it.
are they the one's i need tony ?
ill go with the more powerful resistors as the 80mm fan is not big enough to have to many items on it.
Thanks for the e-mail Tony.
I'm going to go for 8 led's on each fan.
2 each side should be fine as I've got 4 fans to do and that will be 32 led's and I don't want to much as it is under my desk.
I'll order some of those new resistors and hopefully do one fan Tuesday morning and see what it looks like.
I'm trying to go for less cables as the case I've got isnt that great for cable routing and I have a water-cooling set up also.
I'm going to go for 8 led's on each fan.
2 each side should be fine as I've got 4 fans to do and that will be 32 led's and I don't want to much as it is under my desk.
I'll order some of those new resistors and hopefully do one fan Tuesday morning and see what it looks like.
I'm trying to go for less cables as the case I've got isnt that great for cable routing and I have a water-cooling set up also.
Thanks for your comments Dreadi, vti_786, sunjoo2012, Jamiman.
@schizo220168 - Seems that 240 ohm isn't as readily available as some other resistances and you can only get 10 off sets on the bay. They'll be fine but you might be better off going for the 270 ohm here or the 220 ohm here. Neither link is something that OCuk sells so I don't think it will be a problem.
I'd probably go for the 220 ohm as they'll be a tad brighter
@schizo220168 - Seems that 240 ohm isn't as readily available as some other resistances and you can only get 10 off sets on the bay. They'll be fine but you might be better off going for the 270 ohm here or the 220 ohm here. Neither link is something that OCuk sells so I don't think it will be a problem.
I'd probably go for the 220 ohm as they'll be a tad brighter
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Good stuff.
Those LEDs should only take a few days (a week tops)if you got the ones from the listing I sent you, I've had a few deliveries from those guys and they've generally been quick. They usually take up to 14 days if you get them from HK or China though.
Those LEDs should only take a few days (a week tops)if you got the ones from the listing I sent you, I've had a few deliveries from those guys and they've generally been quick. They usually take up to 14 days if you get them from HK or China though.
Hmm I've had LEDs from Hong Kong quicker than a week. If he says he has sent them then I'd sure he has, I never had any problems with that seller. I'm sure I had some from them the very next day after ordering.
@JoeFX69 - Thanks, I know it still amazes me how good they look.
I've been meaning to take a video of them and get them up on youtube but never seem to get around to it, they look even more awesome in the flesh I can tell you. The wife says my computer look likes it on fire with all the orange colour bleeding out of every hole.
@JoeFX69 - Thanks, I know it still amazes me how good they look.
I've been meaning to take a video of them and get them up on youtube but never seem to get around to it, they look even more awesome in the flesh I can tell you. The wife says my computer look likes it on fire with all the orange colour bleeding out of every hole.
first lot of led's still haven't turned up.
contacted him and he is sending out another set (free of charge) via 1st class recorded so should get them today or tomorrow.......fingers crossed.
but ive got everything including the new resistors now so just the led's im waiting on.
even drilled out the fans already.
contacted him and he is sending out another set (free of charge) via 1st class recorded so should get them today or tomorrow.......fingers crossed.
but ive got everything including the new resistors now so just the led's im waiting on.
even drilled out the fans already.