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

Greets,

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
https://www.meanwell-web.com/product_info.php/products_id/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?

Thnx

JB

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steveastroukBest Answer (author)2013-03-28

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.

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MistaMasta (author)steveastrouk2013-03-28

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?

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steveastrouk (author)MistaMasta2013-03-29

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.

Steve

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MistaMasta (author)steveastrouk2013-03-29

Thnx,

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

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steveastrouk (author)MistaMasta2013-03-29

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.

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MistaMasta (author)steveastrouk2013-03-30

The 0R5 resistor is that a 0ohm resistor?

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

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MistaMasta (author)MistaMasta2013-03-30

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

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steveastrouk (author)MistaMasta2013-03-31

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

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steveastrouk (author)MistaMasta2013-03-31

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

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MistaMasta (author)2013-03-30