Would you buy a no-name-brand high power LED for the extremely high price from somebody that you never heard about??
How will you cool it? With liquid nitrogen?
Well, at 35v and 2.5a (average specifications), the input power would be 87W. To get out 100W out would be very impressive!
An LED like that is going to give out a LOT of heat, and have a lowish efficiency (as LEDs go). I'd expect more like a 130W input for 100W of light, at least.
CFL bulbs give number for how many watts they use, but also give a number of watts, pertaining to an 'equivalent' incandescent bulb. People see the numbers they are familiar with, and generally disappointed with the performance. Suspect LED replacement bulbs do the same, but are much worse, since the light is more direction. I've also seen some 10w LEDs, but were multiple LEDs on the same die, lots of heat, expensive failure...
I have one of those 50W high power LEDs. There are 50 1-W LEDs in the package (5 rows of 10) and it almost looks like each die was placed by hand.
The forward voltage isnt well matched either. Need to run it at about 5W for all of them to turn on. I wouldn't be surprised if some of them burn out pretty quick.
I have it mounted to a CPU heatsink. gets hot after a minute or two, but it should stay cool with a fan on it.
CFL bulbs give number for how many watts they use, but also give a number of watts, pertaining to an 'equivalent' incandescent bulb. People see the numbers they are familiar with, and generally disappointed with the performance. Suspect LED replacement bulbs do the same, but are much worse, since the light is more direction. I've also seen some 10w LEDs, but were multiple LEDs on the same die, lots of heat, expensive failure...
That is the problem with my project right now. Not getting the brightness I need.
I am using 20K mcd LEDS. 5mm driven directly from 220V @ 20Ma.
24 of them driven with a very simple reliable circuit. The high power LED'S want a minimum of 350 Ma. My simple /cheap/reliable PSU can only accommodate around 30 Ma. So basically..I am (swearing removed). Damn.
LED's are brighter when pulsed. They last longer when pulsed. They use less energy when pulsed.
Also, when you drive them with a high current, they will not last long and they will produce a lot of heat.
No!
Your vision dims a light that is on for less than about 30ms which is why PWM is used for light dimmers. The width of the pulse determines the brightness.
But if you pulse an LED then you must increase the current for it to be seen as bright as a continuous LED at a much lower current. Increasing the current increases the forward voltage that increases the anount of heat. Also look at the high current used for a multiplexed display to be seen brightly.
LEDs are absolutely not brighter when pulsed. The efficiency (lumen/W) of LEDs decreases with current.
For instance if you drive an XP-G @ 1W you get 130 lm/W, at 3W you get something like 95 lm/W.
So a constant 1W power gives you 130 lm, a PWM of 3W at 1/3 duty cycle (total 1W) only gives you about 95 lumen.
So if you want dimming and good efficiency at low power, use a suitable constant current, not PWM drive.
HOWEVER the color temperature depends on the current. If you want constant color temperature at all dimming settings, then you need to use PWM.
About the 100W LED :
You should use that only if you need an ultra bright source which is also very small. Underwater or not, getting 100W out of such a small thing is going to need real thought, and a big piece of copper. Perhaps a CPU cooler.
On the other hand, using 3/5W LEDs, spread around a reasonable surface, you won't have problems. The LEDs will run a lot cooler (and thus, more efficient).
Also if you use standard "star" pcb LEDs you can mount the optics of your choice (although water must not come in contact with the total internal reflection plastic optics, or else you don't get any internal reflection, and the optics are useless).
Has anybody here have experience driving multiple LED's directly from 220VAC?
I know the Christmas lights LED thing......simple etc..
One thing I cannot understand with my project right now is that an X2 Suppression Cap rated @ 275 VAC and 0.47 MF heats the other parts more than a standard rated 0.47MF @ 630V DCCap.
Please correct me if I am wrong. An X2 Cap is designed for continious AC operation across the Mains. This is a normal Cap right but really high quality ?
A 0.47MF is a 0.47MF right ?.
What is special about the X2. It is truly giving me a "mind buzz".
If you are not using a full-wave bridge rectifier and a big filter capacitor then your LEDs are not bright because they are turned on for only half the time.
A capacitor that heats at the very low mains frequency is defective. It should produce no heat.