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Author Topic: Powering 200W LEDs  (Read 2109 times)
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Helsingborg, Sweden
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Hello!

I have very limited knowledge about electronics, but a very good idea  smiley-mr-green

I want to control 200W of RGB-LEDs with my Arduino Duemilanove, both dimming and color. What is the best solution to reach the required power?

My thoughts goes like this. I use three PWM-pins to controll each color in strength, and could in that way create any color in brightness 0-100%...
Is it possible to just add an amplifier between the board and the LEDs? Or is it not possible to amplify the PWM-output?

Greatful for beginners help
Marcus
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Norway
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Depending on the led's you are going to use and the powersource, this is a feasible project.
I think it is best to use FET's.
Using leds in series you can limit the current use of your powersource and skip the need to use resistors and such.

If you share more details about the project, i and others can provide you with better answers.

Cheers
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Manchester (England England)
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You should only use a resistor to limit the current if the current in the LED is about 40mA or less. If a LED takes more than this then you need a constant current driver for each LED or series string of LEDs. As RGB LEDs are often common anode or common cathode you can't put these in a series string. Only if you have access to both cathode and anode can you put them in series.
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Helsingborg, Sweden
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Ok. I will try to explain a little more about my project.
I want to control both color and brightness of 20 RGB LED-strips. Each strip contains 45 RGB LEDs, in total 20 strips times 45 LEDs = 900 LEDs. Each strip is rated 9.8W, in total 196W.
I´m using the Duemilanove board and has so far connected three seperate LEDs, one red, one green, and one blue, to three PWM pins set for output, just to learn.

I´m assuming that it will be possible to use the board with some kind of amplifier to drive the strips... but I don´t know how. Is it possible? To amplify the PWM-output?
The strips should be driven by 12VDC, 16,3A?? I´m really at the bounds of my skills here.

Next step in the plan will be to send, via wifi, input data from a Iphone-app to the Arduino, regarding brightness and color.
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Helsingborg, Sweden
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Thinking a little bit more. Is it a RGB LED driver i need? And in that case, I assume there is a way to hook up the Arduino with the driver...
When I read about PWM-dimmers I can see that they are supposed to be connected after the driver... can I input a PWM current into the Driver?

Sorry for being confused
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I'm building an RGBW LED floodlight.. which in function is really the same thing as your design.

What we need to know is the type of LED strip and it's wiring.  What you want is is each color to be an isolated circuit, with the LED's strung together in series and both the positive and negative connections available.  Your current supply circuit feeds the LED's positive and your PWM transistor acts as a switch between ground and the LED strip.  Given that number of LED's and the currents/voltages, you'll probably break it down across several supply/sink setups to keep it reasonable.
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Actually... I think this is a lot easier than you think.

I'm pretty sure your LED strips already have resistors in place. You don't actually need to amplify the PWM signal at all, you just need a component on each PWM output capable of switching a much larger source.

You're just going to need a transistor (there are many many articles about these) and a 12v supply capable of putting out 200w.

Ohms law says 200w @ 12v is 16.67 amps... maybe there is a better way to do it though. I think this is a start!

I'd say start with 1 strip of LEDs and then graduate up to the larger project smiley
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All you need 3 power MOSFET, logic level.
Check with SparkFun, they should have some.
For power supply you can use unit from PC
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Helsingborg, Sweden
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Thanks!

It´s becoming clearer. How many amps could I put through the board, VIN-pin? Can I send 20A through it?

Will check for MOSFET´s.
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Manchester (England England)
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You don't put amps through an arduino, you power it with a voltage and it takes the amount of current it needs (amps).

If you feed a voltage into the Vin pin then the most you can take out of the +5V pin is about 650mA (depending on the actual voltage on Vin). This is due to the power dissipation on the internal regulator.
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High current should not go via board, look at this as an example how high power motor is controlled by microcontroler:
http://www.neufeld.newton.ks.us/electronics/?p=133
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If you'd rather just spend $40-$60, try this:
http://www.hiline-lighting.com/pd-rgb-led-amplifier-6a-per-channel.cfm

If your strips are common anode (the vast majority are), products like this are easy and fast ways to do what you want. YES, you can absolutely do the same thing with power MOSFETs, and I have.  This is just the type of device I personally go to when I want to do it all quickly.

A google search for RGB LED amplifier will show you thousands of alternatives. 

Seller Ray Wu on aliexpress.com sells inexpensive units that are good quality. 
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Helsingborg, Sweden
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Aha, RGB LED amplifier, what is the V input for? I use common anode strips.
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On the this site you could see the power supply going through the boards VIN-pin. But as I understand it this is a bad idea!?

http://danielkennett.org/blog/2011/09/arduino-dioder-part-one/
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Vin is the same as the power input jack (except the series diode) so it is perfectly acceptable to put power into this pin.
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