# "I need some guidance, please" - " i want to power six 10 W led-s."

#### Rizalex

Joined Mar 25, 2016
6
Hi. Im not that new to electronics but Im having some problems figuring this out.
The basic idea is that i want to power six 10 W led-s. They have a Vf of 9-12V and
a current draw of 1050 mA (china). I also want to buy a 12 V power supply 16.5 amps
or something like that. In the past i have used 12 V led-s and connected them directly to the
power supply and they worked fine. Is is true that the current draw from the source was getting
higher and higher as the led-s temperature climbed. This time around i want to limit the current that
the led-s take in. For that i want to use the LM317. Now, with the 317 i want to use a 2W 1.5 ohm resistor.
I want to limit the current draw to about 800 mA. I dont know for sure that the 12 volts from the power supply
will be enough to power the led-s. So could anyone give me some advice on this matter.
Tanks a lot!

#### wayneh

Joined Sep 9, 2010
17,167
The normal application of the 317 is a voltage regulator and in that circuit it has too large a dropout voltage for your application. It also can not handle a 1A load without a big heat sink.

You need a current regulator. The 317 can be used for that but by the time you add an external transistor, you might as well get a DC-DC converter rated for your load.

#### Rizalex

Joined Mar 25, 2016
6
Yes. Probably the use of the 317 is not the best one in my case because of the big heat sink and also i have to make one circuit for each of the led-s. What is the best way to power the leds? Lets say i want to power just one. Can i use a 12 volts 10 amps power supply designed for led strips? OR this will damage the led unless i have something that will limit the current that can be used by the led?

#### #12

Joined Nov 30, 2010
18,223
Not being one to tell you how to do your business, I just show you how.
The TO-220 will have 108 C die temperature if you apply an infinite heat sink. I think a TO-3 metal can is the only answer for a chip like this in a job like this.

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#### Rizalex

Joined Mar 25, 2016
6
But still. Can i power the led straight from the led strip power supply?

#### wayneh

Joined Sep 9, 2010
17,167
Lets say i want to power just one. Can i use a 12 volts 10 amps power supply designed for led strips? OR this will damage the led unless i have something that will limit the current that can be used by the led?
That won't work, since the 10A control would try to drive 10A through the single strip. You need a current control for
each strip. If you use a higher voltage, you can put strips in series. A single controller can control multiple strips in series.

#### mcgyvr

Joined Oct 15, 2009
5,394
I highly suggest meanwell LDD drivers.. They are around \$5 each and you would use 1 for each LED and need a 24V power supply (of sufficient wattage)..
12V will not work as the Vf of the LED's could be 12V already and you need about a 2V overhead for the LDD's.. (next logical power supply is 24V.. or a 19V laptop supply)
Each (LED + Meanwell) is simply wired in series with the power supply..
They also make 5-up,etc.. PC boards for the LDD's with the through hole pins

Now there are many other ways.. But I always recommend meanwell drivers with ANY high current LED application vs cheap chinese drivers commonly found on ebay or attempting to roll your own for only 6 LEDs..

This will work great for you and run them at 700mA..
and IF you ever want dimming they accept a 5V PWM signal (right from an Arduino PWM pin or similar)

Use this one if you want 1000mA

IMO you will spend more in time/money trying to roll your own or have to use resistors that just give off heat and don't regulate the current in the event of changing Vf or Vin

#### Rizalex

Joined Mar 25, 2016
6
Thank you very much for the answers.
As this project is meant for an aquarium lightning, i decided to take another route.
Since using 10W led-s imply using more then a 12 v power supply and the actual leds
i started to look for other ways to power the light for my aquarium.
So i decided to go for the 5050 led strips. Now, since i want to grow my plants with it i
want a little red and a little blue in the lights. I have to mention right now that i dont want
RGB led strip. I want 6000-6500k white and maybe half a dozen of the red and blue led.
Does it make any difference if i connect a 3 led red strip in series to my big 5 meter led strip?
Since it is powered by 12 volts im thinking that the should not be any problems.

And another question. I saw on the internet that you could buy 110/220 AC led strips.
So instead of giving the strip 12 volts, you buy a little adapter that plugs into the outlet which has,
what i believe it is, a ac to dc rectifier and in the end the strip still gets 12 volts.
Am i right or am i wrong? It would be way easier to bypass the power source all together and would
make this project just a little bit easier. Thank you very much.

#### mcgyvr

Joined Oct 15, 2009
5,394
We don't like to guess..
Typically those 5050 strips use a regular ac/dc adapter anyways so I'm not sure whats the difference between those and the 110/220 AC led strips you talk about (could be nothing is different but without links we don't know)

And...Use caution with AC voltages around water..

#### Rizalex

Joined Mar 25, 2016
6
http://www.aliexpress.com/item/AC-2...3856713.html?spm=2114.40010508.4.2.BQa2ge&s=p

This is a comparable product and i believe that 220 AC is not the best way to go with my project.
It seems that the input is 220 and also the output is 220 AC. And it is to dangerous have 220 that close
to the water.

In the end i believe that the best way is to buy a 12 volts power supply and stick with the 12 volts led strips.

So in regards with the combinations of colors not using the RGB strips, can i pair sections of any color with
the white one, am i right? If i want to replace a single white led with a red led with its respective
resistor will this work? I mean, in a section of tree white led-s (white leds), if i want to replace a white one
with a red one (and the resistor - i say with the resistor because i know that the are different values for white,
red, blue led and so on) will i get who white leds and a red one all glowing at optimal brightness?

Thanks guys!