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Discussion Starter · #1 ·
I have a Antec 900 case and have been thinking about modding the LEDs for a while. I like having them however if I need to keep my computer on a night they get pretty annoying while trying to sleep.

I want to mod the case/fans/leds so that I can flip a switch to turn them off/on. I'm thinking of just putting a hole in the back of the case and putting the switch through there.

EDIT: Finished it.

So everything is working perfectly, all LEDs shining and the switch went in pretty quickly. The brightness of each LED is about the same so the values in that table must have been pretty accurate.

Pics are a bit fuzzy...

Anyway heres the switch:
3hxL8.jpg


And from the outside:
OBuG5.jpg


So yea thats it. Thanks for the help, particularly that table with the forward voltage/current values for different colors of LEDs.
 

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most led fans have them wired in series
you can cut one lead and add a switch/relay to it to control all of them

it wont be easy, and will be alot of extra wires to hide
 

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Discussion Starter · #4 ·
I'm not sure if they are in series or not. Each have separate connection coming out of the circuit board in the middle. The wires to/from each LED are not really convenient to work with. I'm thinking that I might just use the +5V and a ground coming from the power supply to power all of them. Using the 5V supply is probably to much power for the LEDs so I'm assuming that I'll have to put a resistor in series with them. Anyone know what the voltage that a typical (case) led uses?

Yea I knew it wasnt going to be easy, I still want to do it though.
 

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Quote:


Originally Posted by ffejrxx
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most led fans have them wired in series
you can cut one lead and add a switch/relay to it to control all of them

it wont be easy, and will be alot of extra wires to hide


I would Just use the and existing +12v rail or +5v Rail then use a calculator mentioned below to find the right resistor to place inline.

dont let this discourage you. LEDS are pretty simple, Just figure out your source voltage and get the specs on your chosen LEDS then use a LED Calculator like this to design your new array.
 

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Discussion Starter · #6 ·
Quote:


Originally Posted by cook
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I would Just use the and existing +12v rail or +5v Rail then use a calculator mentioned below to find the right resistor to place inline.

dont let this discourage you. LEDS are pretty simple, Just figure out your source voltage and get the specs on your chosen LEDS then use a LED Calculator like this to design your new array.

Thats my only problem at this point, I don't know the specs of the diodes. Are there typical values? Diodes that I have used building circuits in breadboards were pretty tolerant, but I still don't want to blow anything...

If I had a multimeter on hand I would just use that to measure the voltage and current coming to the LEDs from the fan, sadly I don't
 

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uuh led in series?
wth.gif


i acedenly cut the wire to the led on the fans of my tricool and the other 2 leds light up perfectly fine
 

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Discussion Starter · #8 ·
Quote:
Originally Posted by nukefission;11736238
uuh led in series?
wth.gif


i acedenly cut the wire to the led on the fans of my tricool and the other 2 leds light up perfectly fine
Well then they are in parallel, or some complicated random configuration. Ill just cut one and see if they all go out, simple enough.

I just need to know what an average voltage/current for LEDs are. They must all be pretty similar.
 

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most led's are 1.2-2v, 3-4 in series for a 5v circuit is about right

alot of blue led's are higher, 3v+, thats probably why they are wired in parallel
 

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Quote:
Originally Posted by ffejrxx;11739209
most led's are 1.2-2v, 3-4 in series for a 5v circuit is about right

alot of blue led's are higher, 3v+, thats probably why they are wired in parallel
The LED's will defiantly work in the mentioned range. Here is a sampling by color.

LED Color chart

for most dome type LED's this chart will help you find the FV (forward voltage), and rated amperage you need for the calculator I posted earlier.
 

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Discussion Starter · #11 ·
Ok so I figured out what I'm going to do given the values in the table, which was exactly what I needed btw. The calculator gave me one set up but I didn't like how it put a resistor (9 total) in series with each LED when you could just stick a single one in series with the whole array.

I'm going to put all of them in parallel with each other, wired to the switch, then that will be in series with a 8ohm resistor. Should give 3.6V and 20mA to each LED. Now I just need to solder and wire it all up. Hopefully my math is right
eek.gif
 

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Discussion Starter · #13 ·
I don't think that I need a 10W resistor.

Using 20mA through each LED gives 180mA through the single resistor. Also each LED will need 3.6V across it based on the table.

So setting up a KVL equation around a loop in the circuit with a 5V source gives 5=(.18)R + 3.6. Solving for R gives 7.77ohm, which is why I said 8.

P=VI and V=IR, giving P=R(I^2).

Going with a 10ohm resistor gives us P=(10)(.18^2) = .324 W. So a 1/2 watt resistor should be enough.
 

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Quote:
Originally Posted by Xazen;11763337
I don't think that I need a 10W resistor.

Using 20mA through each LED gives 180mA through the single resistor. Also each LED will need 3.6V across it based on the table.

So setting up a KVL equation around a loop in the circuit with a 5V source gives 5=(.18)R + 3.6. Solving for R gives 7.77ohm, which is why I said 8.

P=VI and V=IR, giving P=R(I^2).

Going with a 10ohm resistor gives us P=(10)(.18^2) = .324 W. So a 1/2 watt resistor should be enough.
yea 1/2 watt resistor is more than enough. A 10w resistor is extreme overkill for what you are doing. I think RadioTrash Usually stocks a pretty good assortment of 1/2 watt resistors and anything from 8-12 ohm should suffice if you cannot find a 10 ohm.
 

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Quote:
Originally Posted by Xazen;11763337
I don't think that I need a 10W resistor.

Using 20mA through each LED gives 180mA through the single resistor. Also each LED will need 3.6V across it based on the table.

So setting up a KVL equation around a loop in the circuit with a 5V source gives 5=(.18)R + 3.6. Solving for R gives 7.77ohm, which is why I said 8.

P=VI and V=IR, giving P=R(I^2).

Going with a 10ohm resistor gives us P=(10)(.18^2) = .324 W. So a 1/2 watt resistor should be enough.
After Re - Examining this I decided to simulate your array. Considering the Source voltage is 5v and the draw of Each led is 3.6v The system needs to be set up to have an ~82ohm 1/4w resistor/ Per LED.

If you use a 12v supply you could use 3 arrays of 4 LEDS with a 68ohm 1/4watt resistor.

232323232%7Ffp63389%3Enu%3D3385%3E976%3E846%3EWSNRCG%3D3363%3B2%3C34%3B344nu0mrj


an 8ohm resistor will work for a short period of time, considering the LED could probably handle 5v for between 2 seconds to 48hours. But to bring down the source voltage to the proper range you will need more resistance and making a series array of leds is out because it would so under-power the leds they would not light up at all.
 

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Discussion Starter · #16 ·
That is what I was considering at first, as that is what the calculator gave me. However the same result can be achieved by removing each resistor that is in series with the LEDs, and instead add a single resistor after the 5V source but before all of the LEDs that are in parallel. To lower the current to something that the LEDs can handle over a long period of time all that I would need is a 8ohm resistor in this configuration. I already worked out the math. I will probably use a 10ohm just because.

Anyway its coming along. I already cut the wires to/from each leds, soldered wires to them, and put them all in parallel. Now I just need to fit the switch to the back of the case somewhere and solder the power and wires to the fans to it.

Thanks for the help cook, +rep.
 

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Quote:
Originally Posted by Xazen;11775288
That is what I was considering at first, as that is what the calculator gave me. However the same result can be achieved by removing each resistor that is in series with the LEDs, and instead add a single resistor after the 5V source but before all of the LEDs that are in parallel. To lower the current to something that the LEDs can handle over a long period of time all that I would need is a 8ohm resistor in this configuration. I already worked out the math. I will probably use a 10ohm just because.

Anyway its coming along. I already cut the wires to/from each leds, soldered wires to them, and put them all in parallel. Now I just need to fit the switch to the back of the case somewhere and solder the power and wires to the fans to it.

Thanks for the help cook, +rep.
Thanks!

no problem

I was having a hard time visualizing what you where saying. After the simulation, Right on. With an 8 ohm resistor you would be running 3.2v which is more than good. Here is what I tested just for giggles and +rep for your math equation goodness.
232323232%7Ffp63398%3Enu%3D3385%3E976%3E846%3EWSNRCG%3D3363%3C849%3C6344nu0mrj

232323232%7Ffp73395%3Enu%3D3385%3E976%3E846%3EWSNRCG%3D3363%3C79%3B%3C8344nu0mrj


Oh yea and here is The Circuit Simulator I used in the event you want to test further. Make sure you have Java installed on your system as this is a .jar.
 

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Discussion Starter · #19 ·
Quote:
Originally Posted by cook;11776424
Thanks!

no problem

I was having a hard time visualizing what you where saying. After the simulation, Right on. With an 8 ohm resistor you would be running 3.2v which is more than good. Here is what I tested just for giggles and +rep for your math equation goodness.

Oh yea and here is The Circuit Simulator I used in the event you want to test further. Make sure you have Java installed on your system as this is a .jar.
Awesome simulation btw. Will defiantly keep that site in my bookmarks.
Quote:
Originally Posted by RIFOLWANTS2BUY;11776458
you could just wire all the leds to one negative and have a switch on that one neagtive
Yea that's pretty much what I did. However the resistor was needed in order to keep limit the current to something the LEDs could handle.

Anyway I spent most of the day today wiring everything up. It took a looong time, there were a ton to wires to solder. Not to mention the wires to the anode and cathode of each LED were absolutely tiny and impossible to work with. I'll post a pic or two later.
 
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