- Joined
- Jun 30, 2002
- Location
- Boise, ID, USA
Hey I am gonna set up an LED in the frot of my case so do some esigns. how do I hook the LED up?
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Led?
- Thread starter Intrepid
- Start date
- Joined
- Jul 17, 2001
- Location
- Denver, Colorado
actually it's a bit more complex than that.
First, figure out the LED's forward voltage- usually around 2V. Should sy on the package. Then, you need to find the proper resistor to drop the +5V (red wire) line of that drive connector in your picture to match the LEDs requirements.
The magic LED formula is:
(current used - forward voltage)/forward current of LED in amps = value of resistor in ohms. it'll look like +5V - 2.1V/.025a = 116ohms, for example.
Put the resistor on the + leg of teh LED and you are good to go! Or just go out and by LEDs prewired with a series resistor to make it even easier
First, figure out the LED's forward voltage- usually around 2V. Should sy on the package. Then, you need to find the proper resistor to drop the +5V (red wire) line of that drive connector in your picture to match the LEDs requirements.
The magic LED formula is:
(current used - forward voltage)/forward current of LED in amps = value of resistor in ohms. it'll look like +5V - 2.1V/.025a = 116ohms, for example.
Put the resistor on the + leg of teh LED and you are good to go! Or just go out and by LEDs prewired with a series resistor to make it even easier
- Joined
- Apr 25, 2001
- Location
- Philthadelphia
If you don't have your LED's yet, you can get 12V ones at Radio Shack, and I think 5V ones too. Come in green red yellow and even dual color ones. As Monster said, Red is 5V and Yellow is 12V, and their coresponding grounds are directly next to them.
-Rav
-Rav
OP
- Joined
- Jun 30, 2002
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- Boise, ID, USA
- Thread Starter
- #4
I already have the LEDs witch I got frome the shack. I have 2 of them, red LEDs 1.7volt 20mA 800mcd Forward voltage 1.7typ 2.4max, what will I need for that?
OP
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- Jun 30, 2002
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- Boise, ID, USA
- Thread Starter
- #5
Can I stack resistors? is there any special rule for doing that? I need 165ohms.
- Joined
- May 28, 2002
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- Sector 7G
Three 56Ohm resistor's.
OP
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- Jun 30, 2002
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- Boise, ID, USA
- Thread Starter
- #7
um...how does 3 560s = 1 165?
- Joined
- Jul 17, 2001
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- Denver, Colorado
yep, you can join together resistors. Like, a 100ohm plus a 50 ohm res is equal to a 150ohm. Makes sure you put them in series and it'll work fine.
But, if you need 165ohms, just get you a 150ohm one from RadioShack. It's close enough- a bit off either way won't hurt it.
See how it says on it 1.7typical 2.4 max? The LED will be happy with forward voltage anywhere between 1.7 and 2.4. So you can be quite a ways off with your resistor and still have it work perfectly.
But, if you need 165ohms, just get you a 150ohm one from RadioShack. It's close enough- a bit off either way won't hurt it.
See how it says on it 1.7typical 2.4 max? The LED will be happy with forward voltage anywhere between 1.7 and 2.4. So you can be quite a ways off with your resistor and still have it work perfectly.
OP
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- Thread Starter
- #9
so would a 100ohm resistor be ok? I have 5 of those i bought to drain my psu caps.
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- Jul 17, 2001
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- Denver, Colorado
That might be pushing it. Give it a try; if the LED seems like unnaturally bright then try using two 100s instead.
Even if you do feed an LED too much voltage, it will still last for a somewhat long time before dying on you. Months. heh unless you give it like 12V, then it dies really quick, give it a try it's cool lol
Even if you do feed an LED too much voltage, it will still last for a somewhat long time before dying on you. Months. heh unless you give it like 12V, then it dies really quick, give it a try it's cool lol
OP
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- Thread Starter
- #11
it's prety bright with 2 100s. and i have 2 LEDs and 5 resistors. so i wil have one left for my psu! i think i'll go n buy some 150s tho so i can get the full 800mca
- Joined
- Dec 31, 2001
- Location
- Ottawa, Canada
Say you buy a 5V, 5mm blue LED from Radio Shack...will you need to use a resistor?
Radio Shack CAT No. 276-311
Radio Shack CAT No. 276-311
- Joined
- May 28, 2002
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- Sector 7G
No, you'd just need to splice a Molex connector.
- Joined
- Oct 8, 2001
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- Redmond, WA
Don't buy those resistors! You can get 150 ohms with 3 100 Ohm resistors.
Just solder two of them together in parallel for 50 ohm (it's wierd, but it works), then put that in series with another 100 ohm resistor for a grand total of 150 ohms. I can 'splain why it works if you want.
For a resistors in parallel, the total resistance is 1/(1/R1 + 1/R2 + 1/R3 ... + Rn). If you have two resistors of n ohms in parallel, the result is n/2 ohms.
..or you could just put 5 of the 2.4V max LEDs in series and attach them to the 12V rails.
Eidt: Just noticed that you're from Portland. What part? I used to live in Clackamas.
Just solder two of them together in parallel for 50 ohm (it's wierd, but it works), then put that in series with another 100 ohm resistor for a grand total of 150 ohms. I can 'splain why it works if you want.
For a resistors in parallel, the total resistance is 1/(1/R1 + 1/R2 + 1/R3 ... + Rn). If you have two resistors of n ohms in parallel, the result is n/2 ohms.
..or you could just put 5 of the 2.4V max LEDs in series and attach them to the 12V rails.
Eidt: Just noticed that you're from Portland. What part? I used to live in Clackamas.
OP
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- Thread Starter
- #15
I think I might go for that but I don't have 6 resistors. I think I'll jsut go with 150s, caus I want to use both LEDs. Than I weil have some 100s for draining my PSU capaciters. I'll post a pic of my mod when it's done, you'll love it
