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The leds are getting hot. Help.? Answered

I made this led array as a temporary solution to electricity outage but the leds get quite hot. Is that normal? Is there any better way to make such an array? I have attached pictures. The resistor is 100ohm.

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steveastroukBest Answer (author)2011-09-25

12 V and 100 Ohm resistor, and 3 white LEDs should be about right. How hot is hot ? Can you keep you fingers on them ?

Steve

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frollard (author)steveastrouk2011-09-25

+1

...unless the battery is ridiculous
@14v and 4v leds it makes sense
@14v and 3.7v leds it needs 150 ohm
@16v and 3.7v (worst case I can imagine) 245 ohm

@author. Is it the leds getting hot or the resistors?

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steveastrouk (author)frollard2011-09-25

Its not going to STAY at 14V for long though, once its off charge.

Steve

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Shariq92 (author)steveastrouk2011-10-19

Sorry i was out of country and out of available systems. The leds are hot enough that i am unable to touch them for longer than maybe 5,10 seconds. The resistors are also hot but i thought that was normal.

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steveastrouk (author)Shariq922011-10-19

No, its not really normal, with that size of LED, can you measure the voltage across your resistor and the voltage across you LEDs

Steve

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Shariq92 (author)steveastrouk2011-10-21

sorry cant at the moment. cause i am not at home for another week or so but from what i remember the voltage on the leds was around 3.2. around cause each led had different voltage. I think thats because i am using cheap leds. i dont remember the exact voltage on the resistor though i think it was also around 3.

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steveastrouk (author)Shariq922011-10-21

There's something odd going on, because your numbers make perfect sense, but the overheating does not !

Steve

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Shariq92 (author)steveastrouk2011-10-25

|Its not melting or anything so i guess i will just continue to use it as it is. thanks for your help. any advice if i decide to remake such a lamp??

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steveastrouk (author)Shariq922011-10-25

Shariq,
I look very closely at your board. Did you CUT all the tracks between LEDs on the board ???

Steve

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Shariq92 (author)steveastrouk2011-10-28

yes, otherwise it wouldnt work.
I checked the voltages today. With the battery at 12.2V the resistor is 2.2V and the leds at 3.3V.

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steveastrouk (author)Shariq922011-10-28

Just that, in the picture, I can't see any track cuts.

Steve

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