LED resistor

Kurt_ · Post by **Kurt_** » Sun Feb 26, 2006 3:22 pm

Ok so I need a 27 ohm resistor for my LED mod. I ahd an old one sitting around, and it worked great. It was a bit bigger, I'm guessing a 1/2 watt.

Yesterday at nutech I bought a new 1/4 one. It works, but on power up the LEDS start bright and dim down to less bright (in an elapsed time of about 2-3 seconds)

Is this something I should be concerned about?

P.S. - 27 ohms is what my LED's require.

Post by **Gamelver** » Sun Feb 26, 2006 7:13 pm

hmmmm....either the voltage is starting to get higher, or the resitance is getting greater.....has this happened many times? try testing the LEDs with a 3.6V battery (like from a phone or something) and if they light up, then they're not fried, luckily. also, what are the specs on the LEDs?

just wann be sure 27 ohms is right

...

Kurt_ · Post by **Kurt_** » Sun Feb 26, 2006 7:58 pm

They aren't fried for sure. They just dim down to a lower brightness than they start at.

The specs are...I dunno.

But thy're part number 350-1561-ND off of digikey. I'm using 4 in parallel. They're the 'LED 3MM WHITE WATER CLEAR'

Website · Post by **Life of Brian** » Mon Feb 27, 2006 10:18 am

http://metku.net/?sect=view&n=1&path=mo ... /index_eng

When in doubt...

Kurt_ · Post by **Kurt_** » Mon Feb 27, 2006 3:14 pm

Yeah I actually think I found that...

Well I did on my own and psoted it hre at least.

I know the voltage drop is 1.3V, and the test current for 1 LED is 20mA. Is it safe to go with 80 (since I have 4) as my current? Gamelver or somebody more experinced please answer this one.