Author Options:

Different collor high powered 3 watt led strings on one constant current power supply? Answered


Can i connect 3 different collored led strings to one constant current power supply?

This is my power source, gives min 9v and a max of 48v @ 700mA
Mean Well LPC-35-700

My leds all 3 watt
6 x 630nm red - 2.5v/3v - 750mA
2 x 660nm deep red - 2.2v - 700mA
2 x 460nm blue - 3.4/4v - 750mA

Can i create these string?
1 string with 6 x 630nm = 18v @ 700mA, should have no problem to run, right?
1 string with 2 x 660nm = 4.4v  (9v min from power) 9v - 4.4v = 4.6v / 0.7mA= 6.57 ohm resistor i should add to this string, correct?
1 string with 2 x 460nm = 6.8v (9v min from power) 9v - 6.8v = 2.2v / 0.7mA = 3.14ohm resistor i should add to this string, correct?

Can my power supply handle this? Since it changes voltage.
If i can use this, which watt resistors would i need?

I would also for example like to add 1 potentiometer for the 460nm blue leds
And add 1 potentiometer for the 660nm deep red leds

Am i asking to much here or can this be done?




With a constant current driver, everything goes in series, you don't need resistors, you shouldn't USE resistors. Some (the 750mA) nominal ones will be very slightly under-run, but it doesn't matter.

You CANNOT run parallel strings on a constant CURRENT driver. You MUST not

You can't dim them with a pot.

That would mean that the power supply will only be used for the 6 x 630nm leds, and for the blue and deep red i should get 2 different power supplies that are not constant current, like a normal adaptor and use resistors and potentiometer if i wanted to be able to dim them at the minimum?

Get three decent dimmable supplies, if you want dimming control.
Its POSSIBLE that the ones you chose are "dimmable" on the mains side - some are - I didn't see it on the datasheet though.



The 6 x 630nm leds i dont need to dim, they are always on, so they will use the mean wel constant current driver, connected in series

For the 2 x 460nm i will use a simple non constant current power supply, probably 12v 1000mA with a resistor and all in series. Dimming is done by a pot

For the 2 x 660 i will also use a simple phone charger 5.5v 1500mA
With resistor and pot to make it dimmable.

This should be good enough right?

Cause after this works the way want, i will make some upgrades, by maybe getting real dimmable constant current drivers

But for now i need to fix the first setup

Any other things i should look out for?

I already have adhesive pads, leds will be mounted to alluminimum plate, and added a pc ventilator 12v 0.6

No, It won't work. The 660's won't have any working room above them to control them with.

The 2 x 460, running on 4.4 V, on a 12V supply, will need a 10Ohm resistor of 5W rating, and a pot after that, with a high power rating you'll struggle to find. - you're burning all your unused juice in the resistors. If you do it, use a circuit like the one I've attached, and an LM317 regulator.

trimmable current source.JPGCopy of maths.jpg

The 0R5 resistor is that a 0ohm resistor?

Btw the blue 460nm leds together use 7v, 3.5 each and not 4.4v

Hi Steve,

Thnx for the circuit, i found some parts in an old computer.

This is what i used,
1 x L7805cv voltage regulator ( from an old computer)
2 x 660nm 3 watt each running at 2.2v 0.700mA
1 x 10ohm resistor connect to ground and output
1 x 12v 1.5a power supply

I can run 1 or 2 leds and they are pretty bright, only the L7805 gets hot but i assume thats normal.

What do you think of this setup, will it last?

See pictures

Greets JB

Fortunately you are under-running the LEDs, your circuit is incorrect as you have assembled it. See my notes on your new question

No, its 0.5 Ohm, or half ohm resistor. The R replaces the decimal point

Here are the pictures