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Topic: High Power LEDS Arduino controlled (Read 2305 times) previous topic - next topic

Siberio

Hi to everyone. First of all I would like to say hello, since I'm new in this world. And also excuse me if I post in the wrong section.
In the project I'm working on I need Arduino to control (simply ON/OFF, no dimming at all) 18x 1w coloured HPLEDs and 2x 3w white HPLEDs in order to provide the right light to my young Saguaro Cactus.
There are 2 LEDs for every colour tonality: 2xBlue1, 2xBlue2, 2xGreen, 2xRed1, 2xRed2, 2xRed3, 2xInfraRed1, 2xIR2, 2xIR3 and all of them are 1w LEDs; 1xWhite1, 1xWhite2, both 3w LEDs. A total of 20 LEDs, but not every LED needs to be ON on the same time.
A RTC module determines when every group needs to be turned ON or OFF.
Blue1, Blue2, IR1, IR2 are groups that are always turend on.
White1 is on only on Phase1.
White2, Red1, Red2, Red3 are ON only on Phase2
IR3 has a special program, needs to be controlled alone.
Green is on request and may interact with IR3 special program, but that's not a problem.
All 3w LEDs (White ones) require 700mA, 3.2-3.4V
All 1w LEDs require 350mA.
All blues and green require 3.2-3.4 V.
All reds and IRs require 1.9-2.2 V.

My problem is: how to power the LEDs? Can I use the same power source for both LEDs and Arduino?
I thought to use an AC/DC 12V 60W converter to power them all and place the right resistor for every series of LEDs (2 LEDs in series of the same colour, all in parallel) and switch them using Mosfet IRF 540N. But this seems to be the less efficient way to wire the LEDs: resistors would waste a lot of heat.
I've made my researches and found some other way to solve the problem. One of these is using a ZXLD1350, but I don't know how to use it so I'd say no to it.
I've found this guide.
http://www.instructables.com/id/Circuits-for-using-High-Power-LED-s/?ALLSTEPS
6th step seems to be quite simple and cheap to build.
Also I could use LED Drivers AC/DC or DC/DC.
Using AC/DC driver should force me to control it using a relay to turn on/off driver, right? If I have understood well, turning on an LED while its driver is on may burn it.
Going that way may become too much expensive, but I need to be sure to give the best life expectation to those LEDs...
I have found some Drivers and Power sources, but everything is getting too much confusing...
That's why I'm asking here :)
If more infos are needed, just ask.

jack wp

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I thought to use an AC/DC 12V 60W converter to power them all and place the right resistor for every series of LEDs (2 LEDs in series of the same colour, all in parallel) and switch them using Mosfet IRF 540N

that sounds good, but the highest voltage you need is about 7 volts. So if you can get a 7 volt power supply, it should be pretty efficient, and not much heat from the resistors. Or you could use the 12V, and a high efficiency regulator to drop it down to the range you need (7V ?).
Good luck, Jack

Grumpy_Mike

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I've found this guide.
http://www.instructables.com/id/Circuits-for-using-High-Power-LED-s/?ALLSTEPS
6th step seems to be quite simple and cheap to build.

Yes that is the way to go. You can't use resistors at these powers the result is not stable enough.

Step 5 is more power efficient but harder and more expensive to build.

Siberio

http://www.ebay.it/itm/Constant-Current-High-Power-Driver-for-1x1w-LED-Light-Lamp-12V-MR16-/121177849445?pt=LH_DefaultDomain_0&hash=item1c36c33e65

Could it be a good option? Every led would be wired to one of those and 1 Mosfet could switch on/off group of LEDs

Grumpy_Mike

It would be good for the 1W LEDs but not the 3W ones. It is the output current:-
Output Current: 320-350mA
They are switching regulators so they will be efficient.
Yes they could be all controlled with a FET.

Siberio

OK, I got it!
That was an example, of course the 3w ones would require their own driver.
So I will have 3 main switches (mosfets) that will control 3 main groups of leds, all of them wired in parallel each other.
I was thinking about using 2x 12V 5A power sources to power it all.
About the mosfets: i was thinking about using IRF540N, but someone told me that ann IRL would be better. Any advice about it?
Many thanks again

elac

I use step 8, the second circuit labeled #5 for powering 3w leds from the Instructables link. It works great. Built a few projects using that.
About 75% efficiency.
It's all about the skills

Siberio

Is it hard to build? What about the cost? I have a total of 80 leds to power, with different needs...

Grumpy_Mike

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i was thinking about using IRF540N, but someone told me that ann IRL would be better. Any advice about it?

Yes the L in IRL stands for logic, this means you can simply turn them on with a digital signal direct (through a 100R resistor ) from the arduino. With the other type you have to generate a gate signal of at least 10V to turn it on. You would need to add an extra transistor to do this.

Siberio

As far as I know, also the N in IRF540N means that the mosfet can be turned on with arduino's 5v

Grumpy_Mike


As far as I know, also the N in IRF540N means that the mosfet can be turned on with arduino's 5v

No the data sheet says it is only fully turned on with a gate voltage of 10V. If you give it 5V it will not be fully on, but it might be on enough or a specific appliaction, but hat is not the way to use this part.

Siberio

Thank you very much Mike, now I know a bit more about mosfets. I hope to find a good way to wire leds and power source: many possible ways, but I need to understand the differences and pick the right one :)

Grumpy_Mike

No problem.

Will you be at the Maker Fair in Rome?
I have a stand, come and say hello.

Siberio

I don't know since I still don't know my shifts, but I'd really like!

Talking about mosfets, do they need also a heat sink?

I was thinking about buying 240V AC/DC led drivers . Would they heat?

Grumpy_Mike

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Talking about mosfets, do they need also a heat sink?

Anything needs a heat sink if it is asked to dissipate more than the package alone can dissipate.
You have to work out what power your FET will dissipate, that is the current squared times the on resistance.
Look it up in the data sheet as to what power the package will get rid of. See:-
http://www.thebox.myzen.co.uk/Tutorial/Power.html

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Would they heat?

Everything heats up. The question is by how much.

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