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help with LED

N

NIMAvsWORLD

n00b
Joined
Jan 16, 2004
Messages
58
whats the supply voltaqge of this

because i want to figure out what resistor to put if i want to put 3 LED's together to make this

except, see im using these LED's.

can anyone help me out ? please? what resistor should i use for those type of LED's?
 
Originally posted by NIMAvsWORLD
whats the supply voltaqge of this

because i want to figure out what resistor to put if i want to put 3 LED's together to make this

except, see im using these LED's.

can anyone help me out ? please? what resistor should i use for those type of LED's?
Click to expand...

Originally on the Radio Shack Website
Typical voltage 2.2V, with a maximum of 2.4V.
Click to expand...

You'll be able to use two of those, max, through the 5v on the Xbox's 5v supply. :( Or, you could use 4 and make two groups, and put them on in parallel. That might be hard on the current, though. =\ I'd try to find some smaller voltage LEDs...
 
LEDs use an EXTREMELY small amount of current.

You could run literally hundreds, if not thousands of LEDs from a standard ATX power supply.
 
Originally posted by SarverSystems
LEDs use an EXTREMELY small amount of current.

You could run literally hundreds, if not thousands of LEDs from a standard ATX power supply.
Click to expand...

These are going into an Xbox controller, using the 5v line it uses. ;) So, there is a limit, but in this case, it probably won't be met with some LEDs. 2.2 + 2.2 = 4.4... Lets see... 2.4 + 2.4 = 4.8... You might want to get a TINY resistor (10 ohm should do, methinks, just enough to reduce the voltage by .2 - .4v). Then you should be fine. :)

Two LEDs in series X 2... So, you would wire the + on one LED to the - on the other, then into the +5v and ground on the controller. Then, repeat. :)
 
wait, so, what would be the colors on the resistor and how many can i put on that one resistor?
 
Originally posted by NIMAvsWORLD
wait, so, what would be the colors on the resistor and how many can i put on that one resistor?
Click to expand...

Ummm, I would go to Radio Shack and pick up a small resitor... Let me see if I can find the resistor calculator website.
 
it only uses 10 miliamps

ohms law

watt=volt*amp so youd only use a tiny amount of power
amp=volt/ohms


correct me if im wornt but im pretty sure thats right
 
for resistor color codes remember

bad
boys
rape
our
young
girls
but
violet
gives
willingly

;)

that stands for

black 0
brown 1
red 2
orange 3
yellow 4
green 5
blue 6
violet 7
gray 8
white 9

the 1st number is just a number, the second number is just a number and the third number is how many zeros are after the first 2 numbers

like 22 K ohms would be red red orange because it is 2 2 then 3 zeros

just a quick lesson on resistors and color codes

;)
 
Just curious, but would the same 33 ohm 1/4 watt resistor work in this application. I ask because it is hard to find 1/8 watt resistors. Went to the Shack today actually but they didn't have any, just 1/4 watt. What's the difference? I ask because most calculaters you find on the web won't tell you the watt size, just the ohms.
 
Originally posted by treyrutledge
Just curious, but would the same 33 ohm 1/4 watt resistor work in this application. I ask because it is hard to find 1/8 watt resistors. Went to the Shack today actually but they didn't have any, just 1/4 watt. What's the difference? I ask because most calculaters you find on the web won't tell you the watt size, just the ohms.
Click to expand...

I think it should work as well. You might want to half the resistance, if you're going with higher wattage, but I'm not positive.

It would be easier if you found two LEDs rated at 2.5v or three rated at 1.6v. :p
 
I don't know how the other guys are getting their values, but you want a 100 Ohm resistor if you have the three LEDs in parallel.

Each LED has a forward voltage drop of 2.2V. If you put them in parallel, you will still have a voltage drop of 2.2V across the three LEDs. Each LED wants 10mA, so you have 30mA feeding the parallel combination. If your source is 5V and you're dropping 2.2V across the LEDs, you're dropping 2.8V across the resistor. 2.8V/30mA = 93 Ohms. The closest you'll get to that at Radio Shack is a 100 Ohm resistor.

If you drop 2.8V at 30mA across the resistor, it is dissipating 84mW, or a little under 1/10 of a Watt. A 1/8 Watt resistor would be fine, but they don't really sell those much. It's just as cost-effective to make them 1/4W. The higher wattage will be fine. It doesn't affect the resistance.

Good luck with your project. =)


EDIT: Here's a pic:
led.jpg
 
If you're only using two of those LEDs, you're only pulling 20mA instead of 30mA. So you're dropping 2.8V at 20mA so you'll need a 140 Ohm resistor. The closest you'll get at Radio Shack is probably a 150 Ohm resistor, though. This will work fine too. 150 Ohms +- 10% is Brown-Green-Black-Gold.
 
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