Assuming an external constant power supply, does anyone know if the ratio of heat output (measured at the thermal pads or mcpcb) to input power is linear with XML? I couldnt find anything to illustrate this in the cree datasheets. I dont care about relative fux ratios.
Hypothetically:
If the emitter outputs 2000 btu at 2A, will it output 3000 btu at 3A? I suspect it will output more than 3000, but its just a hunch from all the mods Ive experimented with. For instance, moderately warm running flashlights driven at 2.5A seems to suddenly run HOT when running at 3A. Im fairly certain this isnt just my perception, but I could be wrong.
Watts is watts… so the amount of power dissipated will scale with current. But, heat radiates proportionally to the FOURTH power of the temperature difference.
Pyro makes a very valid point, but I do not think it addresses the question being asked.
Because VF rises with input current, the resulting power dissipation is not linear.
A hypothetical example:
If = 1A, Vf = 2.9V, P = 2.9W
If = 2A, Vf = 3.1V, P = 6.2W
If = 3A, Vf = 3.3V, P = 9.9W
As you can see, power increased in a non-linear way.
The driver’s in a separate box at the back, barely thermally connected to the main chassis. The driver will have its own thermal issues, because of how it’s installed (check my review and mod above to see why).
As a purely theoretical/non-10w-floodlight question, the LED converts input power into one of two things: waste heat or photons. So what I'm getting at is if you hit the point where efficiency starts falling off from the peak, doesn't less lumens mean more of that power is turned into waste heat instead? Like if you had a graph showing all 3, wouldn't the lumens & heat curves start to diverge after a certain point?
I have one of those 500W halogen floods that burnt-out or dropped too many times, can't remember. Anyways it doesn't work anymore so in goes the 20W LED from ebay.
My main hobby is woodworking and one of my pet peeves is not being able to see properly when I'm spray finishing. I need a raking light, which is a light that shines towards or from the side at a low angle to the surface you're working on. I need to see the finish hitting the surface so I can compensate the speed or height of the nozzle. Nothing worst than spraying blind. Anyways I purchase many flood light fixtures and stands in the past but never satisfied with them. Either they are too bright/intense, runs too hot, or not easily adjustable to the height I need.
So when in doubt, build you own. This is what I came up with. Some scrap metal shelving supports and metal framing braces/sheet metal cut to size for brakets. 3 x 10W LEDs. Height can be adjusted between 4 to 6 feet. Ain't pretty but 100% functional~!
Well, it wouldnt have cost me anything… if you hadnt opened your mouth to brag about how much you enjoyed the warm tint. Reading your posts always seem to cost me money and time… darn you!! Now Ive got to mod all of my floodlights before they even get mounted!
The link is also best offer and I dont think any of the completed bids went over $14. There’s also lots of others on ebay. Some come in 5 packs, so dont give up.
The MCPCB wasnt DTP but its definitely copper. I reflowed the emitters onto some sinkpads and will use the copper stars for another project.
The mod wasnt a direct swap. It required a 3/16” inch aluminum plate to lift the MK-R to the same height as the stock COB emitter. I made the shim plate quite large to help spread the heat load and sanded all the surfaces for better heat transfer. I reshaped the rectangular opening of the reflector where it abuts to the emitter to make it dished so it sits flush around the MK-R
Results with driver mod:
Before:
COB CW - 30,100 lux - 13.7 watts
After:
MKR NW - 51,700 lux - 17.1 watts
The neutral MK-R recorded a 72% increase in lux over the stock COB for a 25% increase in power and provides a very noticeable increase in light to the eyes. Even more pleasing is the far better neutral tint and higher CRI over the cheap cold white COB. I think the additional watts measured from the MK-R is because it has a lower vF than the COB, allowing the driver to provide a touch more power.