How to wire LED

Discussion in 'LEDs and Optoelectronics' started by z7master167, May 9, 2013.

1. z7master167

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May 9, 2013
I am trying to wire some uv leds up to a 12v deep cycle marine battery heres what i have done, i bought 4 uv lights at walmart they have 9 uv leds. I soldered one wire to positive and one wire to negeative on all 4 lights. I then took the positive wire from all 4 lights and soldered them together then i took a 10ohm resistor and soldered it on the 4 wires , then i took all the negative wires and soldered them together then i hooked them up to the battery, after a minute or so my resistor turned black and started smoking pretty bad, i on hooked if from the battery and now i dont know what to do i dont wanna burn up the lights

25,497
2,838
Jan 21, 2010
3. glewis721

49
1
Apr 30, 2013
What's your powering situation like? Mabey the resistor couldn't take that much power.

4. z7master167

5
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May 9, 2013
Im using a 12v deep cycle marine battery , from everything ive read, the lights are on parallel theres 9 of them on each circuit board im assiming they are 3.5v amd 25ma so would i multiplt my milliamps 9x25 and use 4 resistors or would i multiply 36x25 and use one resistor im totally dumbfounded when it comes to this

5. z7master167

5
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May 9, 2013
No the resistor was brand new but it was 10ohm and 1/2 watt, on the online calculator it tells me to use a 7.8 watt 15 ohm resistor and thats hooking all 36 lights up to one resistor

6. glewis721

49
1
Apr 30, 2013
Get a resistor that can handle more power.

7. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,497
2,838
Jan 21, 2010
7.8W is a lot higher than 1/2 watt.

Also choosing a 10 ohm resistor instead of a 15 ohm resistor made things worse (for the resistor AND the LEDs).

It would be far more preferable to place a resistor in series with each LED, and even better again to arrange them in strings.

If you can't do this, get a 15 ohm resistor rated at (at least) 10W and use that.

A single resistor like this for LEDs in parallel is likely to result in the individual LEDs having a much shortened life.

8. z7master167

5
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May 9, 2013
Can i wire the led lights up in series even though the lights are wired in parallel? I can run one positive to the + on my battery then the - to the + on the other light and so on to all 4 lights then run the - to my battery from the 4 th light? And if so what kind of resistor do i need then? Anybody have a diagram?

9. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,497
2,838
Jan 21, 2010
You need to re-wire them.

The alternatives are shown in the link I gave you in the second post.

LEDs in parallel are only ever OK if they are both matched and in close thermal contact.

10. z7master167

5
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May 9, 2013
But i wont be able to rewire them they are already on there on circuit board wired in parallel from factory can i not wire in each 9 led light in series to one another?