I have made a power LED assembly today.
4x 10W LEDs are mounted on a Pentium II heatsink using a carrier PCB.
These cheap proto PCBs are good for this actually- they can be worked easily.
I made one test assembly already with 1x blue, 1x red in series.
That runs directly from my laptop PSU!
Current is too low, however. It is only about 500mA.
-I noticed the red LED wasn't very bright at first, but brightness has increased over the past 2 days. Is this normal? Should I expect more increase when I run it at full current?
-The new assembly has 2x LEDs in series. I want to use a large toroid which has a no-load voltage of more than 50V. Rated for 36V x 2.
I want to use a DC/DC converter that is well capable of high voltage.
The problem is when I have larger load, eventually voltage will drop to less than 44V. That is what I will need for all the LEDs in series.
Applying nearly 110V DC to my DC/DC converter PCB is also something I never attempted. It has 12V supply for the TL494.
-Is it better to use all the 4 LEDs in series, or 2x in parallel each?
The transformer isn't optimal for that (48V would be better).
If I have a large voltage difference, I think the DC/DC losses will be higher. All 4 LEDs in series only needs 1A current.
My DC/DC circuit is capable of 10Amps permanently, probably more, and much higher inrush current.
But I am not sure what choice I should make. Maybe I will try with all LEDs in series.
I tried the laptop PSU with 2 red LEDs in series- only very low current. It has just a few volts less than needed!
Actually today I looked at some power LED curves.
The LED forward voltage will increase a lot with current.
Since there are chips in series already, and two or 4 LEDs in series, there are several volts working area. Even a sudden spike of +1 volts won't neccessarily destroy the LEDs with so many in series.
-Question 3. The forward voltage should be 7 to 9V (3 red chips in series). It is even a bit higher than for the blue LEDs! So it is definitively incorrect. Maybe these are white LEDs with a phoshor for red?
I will wire up my PSU soon, inline the Amp meter, and see what voltage is required. And yes the PSU circuit has a current preset also, I made a mistake when I built the circuit, so it actually does not work at all. It won't be so hard to make it working maybe.
4x 10W LEDs are mounted on a Pentium II heatsink using a carrier PCB.
These cheap proto PCBs are good for this actually- they can be worked easily.
I made one test assembly already with 1x blue, 1x red in series.
That runs directly from my laptop PSU!
Current is too low, however. It is only about 500mA.
-I noticed the red LED wasn't very bright at first, but brightness has increased over the past 2 days. Is this normal? Should I expect more increase when I run it at full current?
-The new assembly has 2x LEDs in series. I want to use a large toroid which has a no-load voltage of more than 50V. Rated for 36V x 2.
I want to use a DC/DC converter that is well capable of high voltage.
The problem is when I have larger load, eventually voltage will drop to less than 44V. That is what I will need for all the LEDs in series.
Applying nearly 110V DC to my DC/DC converter PCB is also something I never attempted. It has 12V supply for the TL494.
-Is it better to use all the 4 LEDs in series, or 2x in parallel each?
The transformer isn't optimal for that (48V would be better).
If I have a large voltage difference, I think the DC/DC losses will be higher. All 4 LEDs in series only needs 1A current.
My DC/DC circuit is capable of 10Amps permanently, probably more, and much higher inrush current.
But I am not sure what choice I should make. Maybe I will try with all LEDs in series.
I tried the laptop PSU with 2 red LEDs in series- only very low current. It has just a few volts less than needed!
Actually today I looked at some power LED curves.
The LED forward voltage will increase a lot with current.
Since there are chips in series already, and two or 4 LEDs in series, there are several volts working area. Even a sudden spike of +1 volts won't neccessarily destroy the LEDs with so many in series.
-Question 3. The forward voltage should be 7 to 9V (3 red chips in series). It is even a bit higher than for the blue LEDs! So it is definitively incorrect. Maybe these are white LEDs with a phoshor for red?
I will wire up my PSU soon, inline the Amp meter, and see what voltage is required. And yes the PSU circuit has a current preset also, I made a mistake when I built the circuit, so it actually does not work at all. It won't be so hard to make it working maybe.
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