DIY led questions

[Jdlreef]

Hi everyone,

I am planning my first diy lamp. I already have one led fixture but i always wanted to do one myself.

I wanted to check some doubts regarding the electronics. I don't know how i could limit the current because the leds i am looking have different max current, some 1.5A and others 1.2A.

On the other hand, i dont know if i am missing something else?

Those are the leds I am looking for the project:

royal blue,
warm white,
neutral white,
cyan 490nm,
uv 395nm,
uv 420nm

Thanks to everyone in advance for the help!

 

[Reign1]

You do know you can under drive them .. also are you making them dimmable ??
What LEDs you going with I have a drawer of optics that I never used for CREEs

 

[Jdlreef]

Thank you for the response, yes, I know i can under drive them, but I am not sure how other than using a power supply with 7A or something like that.

To make it dimmable i was thinking about a dimmable power supply.

 

[oreo54]

Thank you for the response, yes, I know i can under drive them, but I am not sure how other than using a power supply with 7A or something like that.

To make it dimmable i was thinking about a dimmable power supply.

First the current is a choice.. Usually they just list maximum current for that particular led.
Like 3w leds are not a 3w but 3w class.. Can take up to 3w (VXA) not need to BE 3w.

I doubt if your diagram is valid for anything.

LEDs are technically listed as current controlled devices but I prefer to look at the voltage.
Say you have one LED that the spec sheet says is 3.6V at 1000mA
If you feed it EXACTLY 3.6V it should draw 1000mA (3.6W)
Feed it 3.5V at it might only draw 700mA (2.45W)

Ok next put a bunch wired in series..
Only thing that matters is their cumulative voltage and what current they can survive at.

Soo say you have 10 leds 5 blue at 3.3V (say 100mA) and 5 violet at 4.0v (say 1000mA)
you solder them all in series +...-...+...- ect;.
Current is related to voltage and vice versa.

You have a constant current driver that is set for 1000mA
5 x 3.3 + 5 x 4.0 =36.5V

So the driver needs to be able to output at least 36.5V
The driver will raise or lower the voltage until the current is at what it is set for.
Doesn't depend on what someone says the current should be.

Ok sort of back to what you have. If you put every led in series and used the ps you have there well just wouldn't light.
Your cumulative V(f) (5 x 3 I guess) is over the conduction voltage after the first 5 leds. You could have a million amps , wouldn't matter.
Use 3 leds (9V) and at 12V it will probably draw enough current to fry itself.

The historically easiest "system" is a bunch of Meanwell LDD-h DC/DC drivers at the current of your choice mated to the power supply that fits your idea of the voltage of your longest string of series leds.

Keep in mind that there is a cost to using these. Generally the voltage capable on the output side is 3-4V less than the voltage of the switching power supply on the input side.