One Luxeon, One Resistor, One Really Big Heat Sink
- Thread starter Ken_McE
- Start date
Doug S
Flashlight Enthusiast
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Ken_McE said:
Is it possible to run a Luxeon with just a resistor to limit its current? Am I guaranteed to melt it down? I'm thinking fixed installation, so I can have as big a heat sink as I like.
[/ QUOTE ]
For many applications this can be a perfectly acceptable design. If you don't need to drive the Luxeon very hard, the heat sink doesn't necesssarily need to be really big.
Ken_McE said:
Is it possible to run a Luxeon with just a resistor to limit its current? Am I guaranteed to melt it down? I'm thinking fixed installation, so I can have as big a heat sink as I like.
[/ QUOTE ]
For many applications this can be a perfectly acceptable design. If you don't need to drive the Luxeon very hard, the heat sink doesn't necesssarily need to be really big.
Re: One Luxeon, One Resistor, One Really Big Heat
I've been watching the threads about this type of thing. I think if you are doing this you need to match the power voltage fairly closely with the voltage of the Lux so you don't have to use a lot of resistance. If you put in a lot of resistance then you use up a significant part of your battery power on the resistor. Try to use the resistor just to fine tune things.
I've been watching the threads about this type of thing. I think if you are doing this you need to match the power voltage fairly closely with the voltage of the Lux so you don't have to use a lot of resistance. If you put in a lot of resistance then you use up a significant part of your battery power on the resistor. Try to use the resistor just to fine tune things.
IsaacHayes
Flashlight Enthusiast
Re: One Luxeon, One Resistor, One Really Big Heat
also, you'll be pulling a lot of power through that resistor (unless your driving a 1W luxeon). 3w/5W you'll need a big resistors, like a wirewound 5w or 3w. Radioshaq sells some .47ohm 5w that I used in my cyan 3C luxIII mod. For 1 w luxeons, a 1 w resistor would work.
also, you'll be pulling a lot of power through that resistor (unless your driving a 1W luxeon). 3w/5W you'll need a big resistors, like a wirewound 5w or 3w. Radioshaq sells some .47ohm 5w that I used in my cyan 3C luxIII mod. For 1 w luxeons, a 1 w resistor would work.
koala
Flashlight Enthusiast
Re: One Luxeon, One Resistor, One Really Big Heat
What sort of input voltage do you have?
If you have 12v, then wire up a 3 1Watt/3Watt luxeons in series so the voltage is close and your resistor won't have to dissipate too much current.
You can also find a power supply that output closer to the input voltage of your luxeon.
What sort of input voltage do you have?
If you have 12v, then wire up a 3 1Watt/3Watt luxeons in series so the voltage is close and your resistor won't have to dissipate too much current.
You can also find a power supply that output closer to the input voltage of your luxeon.
Re: One Luxeon, One Resistor, One Really Big Heat
I've got several direct drive Lux3 equipped lights running on NiMH batteries at approximately 3.6v and 1 amp. Actual current in each of these is slightly different and I find about a + or - 100ma current variation is normal. The two I built (Mag 3C & 3D) have a SWAK Lux3. Max current that I have measured so far was 1.2 amps.
I think I'd recommend an L voltage level rather than the K to stay below 1 amp current. I'm a little concerned about current draw with alkaline batteries or in cold weather. It appears that a .5 ohm resistor will limit max current without a very noticable drop in output. And 1 amp x .5 ohm is 1/2 watt (IxIxR), so a 1 watt resistor should be OK. I plan to use a 2 or 3 watt if I can find one just so the resistor won't get so hot.
I plan to add a .47ohm 5w resistor to each of these in the near future. Maybe I'll use some of this nichrome wire that I have around since none of the Radio Shacks around here have any .47 ohm resistors. I went to 3 different ones looking for KPR112 bulbs and finally found 2 of those bulbs but all of them had a poor selection of resistors. Real electronics stores are hard to find these days.
I've got several direct drive Lux3 equipped lights running on NiMH batteries at approximately 3.6v and 1 amp. Actual current in each of these is slightly different and I find about a + or - 100ma current variation is normal. The two I built (Mag 3C & 3D) have a SWAK Lux3. Max current that I have measured so far was 1.2 amps.
I think I'd recommend an L voltage level rather than the K to stay below 1 amp current. I'm a little concerned about current draw with alkaline batteries or in cold weather. It appears that a .5 ohm resistor will limit max current without a very noticable drop in output. And 1 amp x .5 ohm is 1/2 watt (IxIxR), so a 1 watt resistor should be OK. I plan to use a 2 or 3 watt if I can find one just so the resistor won't get so hot.
I plan to add a .47ohm 5w resistor to each of these in the near future. Maybe I'll use some of this nichrome wire that I have around since none of the Radio Shacks around here have any .47 ohm resistors. I went to 3 different ones looking for KPR112 bulbs and finally found 2 of those bulbs but all of them had a poor selection of resistors. Real electronics stores are hard to find these days.
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