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LED/resistor wiring etc

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IFMU

The Xtreme Senior Nobody
Joined
Jun 21, 2001
Well I've been sitting on a load of LEDs and have been thinking of doing something with them. Just havent figured out what. :shrug:

So a few questions.

First, I know there are different versions. 3v, 5v etc. I am pretty sure all of what I have are one, if not possibly both of that and no other.
What is the easiest way to figure out if they are 3v or 5v? or possibly other?

Next, odds are these will be ran in the PC somewhere/how. So they will more than likely run from the 5v line.
What sort of resistor(s) are needed so as not to fry the LEDs. I can get the resistors info figured out and all. Just not sure as to what resistor(s) would be needed etc.

I'm unsure how I will run them. Series/parallel.
How will that change the resistors needed? I know it will in some way, just not sure how. lol
Had a small class on this stuff and about a quarter of it stuck. :eek:

So any input would be appreciated. ^_^
 

imposter

Member
Joined
May 1, 2004
Location
Bronx,newyork
Well you would need to run them in parallel first of all because if you run them in series you will only be able to run 2-3 of them. remember in a series circuit each led will run as a voltage drop. the leds i worked with in lab took about 1.8-1.9 volts so you would only be able to run 2 of them on a 5 volt line.

the reason why you need a resister for led's is because theoretically LED's are zero ohms or very close to that so using ohms law you will be dividing by a zero or close to it and get infinity amps and thus burn. so what you need to do is calculate the current limiting resistor. this is easy. you need to find the specification sheet of your LEDs and it will tell you what is its rated amperage. then you need to use ohms law to find out what what value resistor you need. then there is the whole business of tolerance.

i would say the easiest way is to post up your specification sheet and i can help you out with the calculations. edit, if you dont know what they are or where the specification sheet is its going to take a bit of trail and error. first of all you should go and buy a protoboard it will make this job really easy. put a high value resister in the circuit then measure the voltage across the resister.

just know you will most likely need to solder these parts.

edit here are some things i built in my Circuit theory class last year. its a simple design but pretty neat when i was a freshman =P.


we etched the boards ourselves.
 

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OP
IFMU

IFMU

The Xtreme Senior Nobody
Joined
Jun 21, 2001
you need to find the specification sheet of your LEDs and it will tell you what is its rated amperage.
problem with that is I have no idea. I've had these for so long...
first of all you should go and buy a protoboard it will make this job really easy. put a high value resister in the circuit then measure the voltage across the resister.
well that sucks cuz that aint gonna happen. No way to afford crap. Which is why I was looking at using what I have here.
just know you will most likely need to solder these parts.
That's not a prob there.l
 

Ben333

Folding for Team 32!
Joined
Feb 18, 2007
You can't afford a 99 cent pack of resistors at radio shack? You don't really need a circuit board, but those aren't really expensive, just a couple of dollars.
 
OP
IFMU

IFMU

The Xtreme Senior Nobody
Joined
Jun 21, 2001
Right now? no. lol
But I have some resistors here already. Got them when i got the LEDs when I was in school.