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Author Topic: little LED problem  (Read 2974 times)

jpantoga

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little LED problem
« Reply #10 on: November 27, 2004, 11:44:00 PM »

Im using 1 resistor, and x24 already helped me out with a little problem I had with the switch, so I should be fine tomorrow.

viridius

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little LED problem
« Reply #11 on: November 28, 2004, 12:18:36 AM »

Quote from: Alric_the_mad
I am stupid when it comes to wiring up LEDs, but I have found that if you use a 10-ohm resistor, you're pretty safe. On the last circuit I built, I used 30 ohms of resistance before an expensive blue LED, on unknown voltage, and it's still running fine.

10 ohms is cutting it a little close.  For a 3.7 volt LED running off of 5 volts, a 10 ohm resistor will limit the current to 130 mA, which is more than six times the maximum current for most LEDs.
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john_is_war

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little LED problem
« Reply #12 on: November 28, 2004, 12:39:21 AM »

okay, the power in that circuit is just over a quarter watt, hence them overheating like that.  You'll either need to get a half watt resistor, or hook one resistor to three of them and another one to two LEDs.
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To-mod-or-not-to-mod

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little LED problem
« Reply #13 on: December 04, 2004, 03:42:19 PM »

I am currently having a smimilar problem, except I have no clue at all. I am just lighting a little nativity up but I bought a lucky bag of LEDs from Maplin and they didnt have any info with them. Just a little bag with 4 types of LED. 6 of each. Is there an easy way to calculate with out the info I havent got?


Any help to anyone...
http://forums.gideontech.com/viewtopic.php?t=22112 ?
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john_is_war

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little LED problem
« Reply #14 on: December 04, 2004, 04:58:37 PM »

multimeter
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viridius

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little LED problem
« Reply #15 on: December 04, 2004, 08:30:39 PM »

A multimeter won't tell you anything about the LED except that it's working.  You could try a 200 ohm or so resistor between 5 volts and the LED, but buying grab bags of unlabeled LEDs isn't such a hot idea.
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TheM@trix

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little LED problem
« Reply #16 on: December 04, 2004, 11:06:06 PM »

Well, I have variable output transformer, so I can test what Led's are rated  at.
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Firespark

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little LED problem
« Reply #17 on: December 05, 2004, 12:40:00 AM »

contrary to what everyone says about resistors, the only things i put leds in are A. short term experiments runnin off 2 AA's or B. prebuilt circuits that already supply the best power. I just dont bother with resistors, so grab bags work out fine for me.
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To-mod-or-not-to-mod

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little LED problem
« Reply #18 on: December 05, 2004, 09:05:33 AM »

Quote from: viridius
A multimeter won't tell you anything about the LED except that it's working.  You could try a 200 ohm or so resistor between 5 volts and the LED, but buying grab bags of unlabeled LEDs isn't such a hot idea.


It seemed like a great buy and I also got a L/bag of potentiometers and Resistors. I also got a l/bag of switches! Its another problem with internet shopping... :-?

Quote from: Firespark
contrary to what everyone says about resistors, the only things i put leds in are A. short term experiments runnin off 2 AA's or B. prebuilt circuits that already supply the best power. I just dont bother with resistors, so grab bags work out fine for me.


That works? I might have to try that!
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Firespark

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little LED problem
« Reply #19 on: December 05, 2004, 12:04:00 PM »

Quote from: To-mod-or-not-to-mod


That works? I might have to try that!


like viridius said, it isnt the best power supply, and it does fluctuate, but i find that with low end led's, they dont tend to care. plus, with a grab bag, if you do fry one, so what? it cost you like a penny.

case in point ive been fooling around with a grab bag of led's from radioshack  for maybe a year or 2, and i have yet to exhaust the supply.
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