"10 watt" LED
A while ago, as an experiment, I bought a 12v outdoor landscape light that claimed 10w warm white. TO NO one's surprise it did not consume 10 watts, and while it did respond to a PWM LED dimmer, th...
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The LED in that light is known as a "COB" or Chip On Board LED.
Consists of 9 1W LEDs.
You will see that there is three rows of three LEDs, the LEDs in each row are in series and the three rows are in parallel.
So, no, it doesn't "consume" 10W, it only will consume 3-4W but give the light of about 10 watts worth of LEDs in lumens.
The little power supply is a constant current switching supply which gives the light a broad input voltage of 10V-30V DC.
It was never designed to be dimmable and to make it dimmable you would need to replace that power supply with either a resistor or a constant current supply which has a adjustable output.
I have played with a few of these COBs and they actually are pretty darn good, I have two similar 10W to yours mounted on my tractor for flood lights on the backhoe. Have had those about 3-4yrs now and they do get used a lot.
Also have bought a few of the bare COBs in 10W, 20W and 50W versions.
Had a super 8mm film projector that used a super rare and expensive 36V 80W bulb that blew out while I was in process of transferring my parents super 8 home movies.
Bought one bulb at $80 and the filament was not centered properly and only would light the bottom 1/3 of the film..
Returned that bulb and got another one, it still had a issue with the filament not centered, so it didn't fully light the film but was better than the first one..
So, I took a stab at building a bulb from a COB LED.. tried 10W, not bright enough, 20W, 30W better but not bright enough, 50W almost perfect match for brightness, slightly darker than the original bulb but doable.
The 10W and 20W can be run from 12V, the 30W and up require min of 30V to light them so to use those with 12V you need a 12V - 36V booster regulator..
The only downside I have found with the early COB design is the color temp selection was outside the projector bulb color temp. I was able to buy specially made color gel films to correct that..
For my projector project, I also bought a collator lens to focus and intensify the light output.. Made a huge difference in the film brightness.
As with any of these high power LEDs, heatsink IS a must, never attempt to run without the chip firmly planted to a chunk of metal.
As far as a resistor wasting power goes, yeah, it will but in reality it is extremely low..
For instance that 10W COB only needs about 10V to start glowing, and around a max of 11V for full rated brightness, current was specd at .370A.
A 12V RV system can get to about 14.4V while charging so we need to drop about 3.4V.
I used a 10 Ohm resistor to accomplish the drop.
That resistor I selected only will dissipate 1.2W of heat..
The switching regulator that is used in those lights typically will consume about .5W of wasted heat..
So, yeah, big deal, using a resistor will "waste" an additional whopping .7W!!!
I suspect that the regulator has bought the farm, to check this you can simply disconnect the regulator board, sub in a 10 Ohm 2W resistor..
If the COB lights fully then the culprit was the regulator..
The advantage of using a resistor is it is cheap and you now can DIM the LED. Just be aware that the dimming range is pretty small since the COB will need at least 10V to start making light..
You can upgrade the COB to a higher wattage, just be aware that to do so will require a boost regulator and you still won't have dimming.
Consists of 9 1W LEDs.
You will see that there is three rows of three LEDs, the LEDs in each row are in series and the three rows are in parallel.
So, no, it doesn't "consume" 10W, it only will consume 3-4W but give the light of about 10 watts worth of LEDs in lumens.
The little power supply is a constant current switching supply which gives the light a broad input voltage of 10V-30V DC.
It was never designed to be dimmable and to make it dimmable you would need to replace that power supply with either a resistor or a constant current supply which has a adjustable output.
I have played with a few of these COBs and they actually are pretty darn good, I have two similar 10W to yours mounted on my tractor for flood lights on the backhoe. Have had those about 3-4yrs now and they do get used a lot.
Also have bought a few of the bare COBs in 10W, 20W and 50W versions.
Had a super 8mm film projector that used a super rare and expensive 36V 80W bulb that blew out while I was in process of transferring my parents super 8 home movies.
Bought one bulb at $80 and the filament was not centered properly and only would light the bottom 1/3 of the film..
Returned that bulb and got another one, it still had a issue with the filament not centered, so it didn't fully light the film but was better than the first one..
So, I took a stab at building a bulb from a COB LED.. tried 10W, not bright enough, 20W, 30W better but not bright enough, 50W almost perfect match for brightness, slightly darker than the original bulb but doable.
The 10W and 20W can be run from 12V, the 30W and up require min of 30V to light them so to use those with 12V you need a 12V - 36V booster regulator..
The only downside I have found with the early COB design is the color temp selection was outside the projector bulb color temp. I was able to buy specially made color gel films to correct that..
For my projector project, I also bought a collator lens to focus and intensify the light output.. Made a huge difference in the film brightness.
As with any of these high power LEDs, heatsink IS a must, never attempt to run without the chip firmly planted to a chunk of metal.
As far as a resistor wasting power goes, yeah, it will but in reality it is extremely low..
For instance that 10W COB only needs about 10V to start glowing, and around a max of 11V for full rated brightness, current was specd at .370A.
A 12V RV system can get to about 14.4V while charging so we need to drop about 3.4V.
I used a 10 Ohm resistor to accomplish the drop.
That resistor I selected only will dissipate 1.2W of heat..
The switching regulator that is used in those lights typically will consume about .5W of wasted heat..
So, yeah, big deal, using a resistor will "waste" an additional whopping .7W!!!
I suspect that the regulator has bought the farm, to check this you can simply disconnect the regulator board, sub in a 10 Ohm 2W resistor..
If the COB lights fully then the culprit was the regulator..
The advantage of using a resistor is it is cheap and you now can DIM the LED. Just be aware that the dimming range is pretty small since the COB will need at least 10V to start making light..
You can upgrade the COB to a higher wattage, just be aware that to do so will require a boost regulator and you still won't have dimming.
