I'm working on parts for assembling a PWM controlled RGB led array. I can get either 1W or 3W LEDs. What's not clear to me is what is best to optimize for light intensity, e.g. would 12 1W be equivalent to 4 3W, in terms of light intensity and power consumption, or is one preferred?
The supplier lists the 1W as 0.35A per channel and 3W as .7A with same voltage drop of ~3V so not sure how they get 3W -- seems more like 2W. Anyway, I'd be interested to hear ideas about how to configure for best light intensity per watt. The driver is constant current and can take 36V in so plenty of room. Another question, should I attempt to match the Vin closer to the total V drop of the array? Would that be more efficient. Thanks
They don't list the lumens unfortunately. But if they did and say it's 120 lumens per led. If you add two leds do you have 240 lumens? From what I can tell lumens are additive but perceived brightness is logarithmic
how to configure for best light intensity per watt.
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For "best lumen per Watt", DO NOT USE RGB, USE WHITE LEDs!
COOL WHITE LEDs provide best "lumen per Watt" ratio.
WARM WHITE LEDs provide less light per Watt.
And using RGB LEDs is the least efficient way to create much light from just a few Watt.
rappa:
They don't list the lumens unfortunately. But if they did and say it's 120 lumens per led. If you add two leds do you have 240 lumens? From what I can tell lumens are additive but perceived brightness is logarithmic
rappa:
If you add two leds do you have 240 lumens? From what I can tell lumens are additive but perceived brightness is logarithmic
ACK.
Using twice the light (doubling the lumens) for illumination will just look "a little bit" brighter to the human eye, but not at all twice as bright. Using 10 times the lumens will look twice as bright, perhaps. The human eye has a logarithmic sensivity to brightness.
jurs:
how to configure for best light intensity per watt.
For "best lumen per Watt", DO NOT USE RGB, USE WHITE LEDs!
COOL WHITE LEDs provide best "lumen per Watt" ratio.
WARM WHITE LEDs provide less light per Watt.
And using RGB LEDs is the least efficient way to create much light from just a few Watt.
Yeah, I need RGB. Perhaps I could have phrased the question differently. Given 1w and 3W RGB LEDs, which is will appear the brightest: twelve 1W or four 3W. I suspect they are not the same brightness
rappa:
Yeah, I need RGB. Perhaps I could have phrased the question differently. Given 1w and 3W RGB LEDs, which is will appear the brightest: twelve 1W or four 3W. I suspect they are not the same brightness
It depends on the cooling and how "hot" or "cool" you are operating the LED emitters.
The cooler you operate LED emitters, the more efficient they will be in generating light energy from electric energy.
Using a bigger heatsink element ==> LED keeps cooler ==> More efficiency
Typically construction of a 3W heatsink should be able to transport three times more heat than a 1W heatsink.
Operating 1W LED emitters and 3W LED emitters should provide same efficiency when operated at same temperatures.
Relevant is the so called "junction temperature" of the emitter.
But junction temperature is just a minor factor for efficiency.
After selecting the wrong type of emiter, i.e. RGB emitter instead of cool-shite emitter, which wastes a lot of light, the temperature just makes a difference of the last 10% or 20% in efficiency.
The easiest/cheapest way is to use a 30, 50, or 100watt RGB COB LEDs (ebay)
3*10-string LEDs on a single aluminium board.
Don't expect white light efficiency from RGB LEDs.
Don't expect white light from RGB LEDs at all.
Not sure what you are using it for, but these COB LEDs are ~$0.10 per watt.
You could use several, combined with cool white or warm white ones.
Leo..
Wawa:
The easiest/cheapest way is to use a 30, 50, or 100watt RGB COB LEDs (ebay)
3*10-string LEDs on a single aluminium board.
Don't expect white light efficiency from RGB LEDs.
Don't expect white light from RGB LEDs at all.
Not sure what you are using it for, but these COB LEDs are ~$0.10 per watt.
You could use several, combined with cool white or warm white ones.
Leo..
Those look interesting but also potentially dangerous for the eyes? What I'm building will go into a decorative box and sit in corner of room and provide run routines, e.g. fade colors across spectrum. I want it to be bright enough but not too bright
Current plan calls for three 3W RGB with a 16V notebook power supply and led driver with PWM control. With all channels at full power it should be about 18W
Three RGB LEDs, mosfet/PWM and a 19volt laptop supply is a bad combo.
Three RGB LEDs (must be 6-pin to be able to connect in series) will drop ~10volt.
Almost half of the power (remaining 9volt) will be lost in the current limiting resistors.
Use five 6-pin RGB starbase LEDs for a VF of ~16.5volt (5*~3.3volt).
Then you only have to drop ~2.5volt in the CL resistor.
Or use a 12volt supply for three LEDs.
Another option is addressable LEDs and a 5volt cellphone/tablet supply for the Arduino and the LEDs.
Leo..
Well I'm not using a mosfet/resistor to drive; I'm planning on using a constant current led driver. Take a look at the AL8805. They claim 98% efficient https://cdn.sparkfun.com/datasheets/Components/LED/AL8805.pdf This accepts an input voltage of 6V-36V.
I looked more at the COB LEDs. The 10W is rated at .35A with a max drop of 11V. So I could use one but two would require a >=24V supply and having a hard time finding one of those that isn't too expensive.
Also the pins on the led are not very clear. If it's a common cathode I cannot use the AL8805 led driver which is not compatible with common anode/cathode
Wawa:
Three RGB LEDs, mosfet/PWM and a 19volt laptop supply is a bad combo.
Three RGB LEDs (must be 6-pin to be able to connect in series) will drop ~10volt.
Almost half of the power (remaining 9volt) will be lost in the current limiting resistors.
Use five 6-pin RGB starbase LEDs for a VF of ~16.5volt (5*~3.3volt).
Then you only have to drop ~2.5volt in the CL resistor.
Or use a 12volt supply for three LEDs.
Another option is addressable LEDs and a 5volt cellphone/tablet supply for the Arduino and the LEDs.
Leo..
Yes, I know those chips. I'm using the PT4115 (same difference).
You can find those on breakout boards on ebay.
One 10watt RGB COB is ok with three switching CC drivers.
350mA through the LEDs will draw ~200mA from the 19volt supply.
You have to use the ones with 6 pins, but most of them have a common bar that can be cut into three.
Leo..
