LED Question!

[scoobydoo2u]

I am in need of lighting 4 White LEDs from one 3V source.
I have used a resistor calculator and it comes up with -24 (LED is 3.3-3.6v from what i see here: FW current 25mA; FW supply 3.3 (typical), 3.6V ) So can I just run these on 3v or not? I'm very new to leds so any help would be great! Thanks in advance!

 

[Rolex]

2 penlight batts is all you need. No resistors.

 

[scoobydoo2u]

Would the same rule apply to any white LED of this size, or just this particular part number?

 

[Rolex]

They will vary in required voltages. If you get one that's ultra bright at 12V, you'll hardly see it at 3 1/2. If you connect the one you have now to a 12V source, you'll get an instant blink, and it's history. Connect it to 9V and it will glow orange till it burns out.
You can run any type of LEDs at a higher than required voltage, provided you use a current limiting resistor.

 

[scoobydoo2u]

I appreciate the help Ralph, but there is one more thing I'm confused about. If I run the values through a resistor calculator and it gives me a negative number do I need a resistor? With these LEDs it says 3.3-3.6 volts, but I am feeding it 3 Volts so I do not need a resistor because it is below the recommended voltage. Correct? I'm Confizzled... Thanks again for your help!

 

[hamz9561]

That's exactly right. Since you're running a lower voltage than the one recommended as the maximum, you won't need any resistors.

 

[Rolex]

Correct, and you won't notice the difference, but at a lower voltage they won't light at all.

 

[scoobydoo2u]

Thank you both for explaining it all to me!