Best bin for least heat??

[Anglepoise]

I am on my second mod and thanks to all you guys, I am happy with what I am learning.

This mod is a fixed light with power coming from a wall wart, through Georges80's excellent Nflex.

The Lux III, I have used to experiment with is a TWAL and the housing stabilizes at around 146°F. I would like to keep the light output as high as possible but reduce the heat a little.

Am I correct in assuming that a 'J' bin will run cooler than the 'L', with the same 750 ma current??

 

[MrMimizu]

I'm not sure that it works that way. It's the amount of current you are putting through the LED that causes the heat. Being at a lower voltage shouldn't make any difference. You might be better off, making a bigger heatsink OR add a little PC fan to help cool your light.

 

[tvodrd]

A lower Vf bin will be cooler at the same If. For example, if your LED needs 4V to achieve 750mA, thats 3 Watts of power in. If your LED only required 3.25V for 750mA, that's only 2.44 Watts of power in. Assuming 10% efficiency, your luminaire will only have to dissipate 2.2 Watts vs 2.7 Watts, and would reach a lower equilibrium temperature under the same ambient conditions. I haven't a clue as to how much temperature reduction would result from a ~20% decrease in input power.

Larry

 

[IsaacHayes]

I'd have to disagree. Power is where heat is from. Power = volts x amps. What about incandecent bulbs that run on low power ~800ma, but 12volts? They get hot with out a ton of current. Hotter than one at 800ma 3v.

A lower Vf means more effiecnt. Means less heat. Watts is a measurement of power. So a lower Vf means it will pull less watts but run at it's rated current and be just as bright.

 

[cy]

gotta go with larry on this one /ubbthreads/images/graemlins/bowdown.gif

lower vf means the lux will put out the same amount of light at a lower voltage, which translates into lower current to produce the same amount of light.

750 milliamps is 750 milliamps, reguardless of what the vf is. difference is one will be driven harder at the same 750 milliamps.

so to produce the least amount of heat. go with the lowest vf possible and underdrive your lux.

also it's not proven, but lower vf luxeon's seems to retain better tint at lower currents. example with two stage switches.

lowest vf is not always best. for li-ion use it's best to match up vf with li-ion's voltage range. Kbin would be excellent for li-ion use.

 

[IsaacHayes]

cy said:[ QUOTE ]
lower vf means the lux will put out the same amount of light at a lower voltage, which translates into lower current to produce the same amount of light.


[/ QUOTE ]
It doesn't translate into lower current to produce same amount of light. You mean lower Wattage, to make same amount of light.

Lower Vf is great for effieciency, battery life and coolness. It is best used in regulated lights. Especailly high current boost as the circuit won't have to pull so much juice from the batteries. Result, super bright drive level with battery life that is still very good!

Lower Vf isn't good for DD, unless your batteries match the Vf. Like DD'ing a TW0H wouldn't be good on 3 cells (pull too much current), but 2 cells would still be pretty bright even though it might not be at full 1amp drive, it would be > 350ma current off of 2 cells!

 

[Anglepoise]

Think I have it now. Thanks all.

 

[idleprocess]

Non-radiated watts (power) = heat, simple as that. You were both saying essentially the same thing.

If you limit power, you control heat. This can be done with any Vf emitter, but you will get more light at any given power level with a low Vf than a high Vf.