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Author Topic: How to use a high current PWM LED controller  (Read 918 times)
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Hi, everyone, i'm a newbie with Arduino so go easy one me  :S

I recently bought two of these http://www.ledsee.com/index.php/new-products/arduino-6-channel-led-shield-035-07-1a-detail for my Arduino ADK and I have no idea how to use them or get them to work. I have it running off its own power supply and i'm using  the fade example sketch which I modified to use pin 2 which the manufacturer says corresponds to output1, but all of the outputs read the same as the input voltage which is 12 volts. I have a feeling I need to create a complicated sketch to interface with the shield but I have no idea where to start.

Can anyone give me any examples or tutorials that will work for this shield? Thanks smiley
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You first have to set the current to match the LED that you have. That board has 3 choices 0,35A – 0,7A – 1A.
Connect it up to a power supply of voltage 6-30V. With the higher voltage you can connect several LEDs in series to be controlled at the same time.
Connect the ground of your power supply to the ground of your Atduino.
Connect one of the PWM pins to one of the board's input.

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I have a feeling I need to create a complicated sketch to interface with the shield
No, just use the analog write function.
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...but all of the outputs read the same as the input voltage which is 12 volts.

You won't be able to measure it until it's under load. The circuit is trying to feed a measured amount of current through the LED; with no LED attached it will read full voltage until it starts seeing current flowing.
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Ah ok. Well I'm running Cree XM-L colour LED's and at almost $30 bucks a pop I'm not gonna play around and potentially blow one of 'em up. I'll try using a RGB strip, which probably draws less than 0.35 amps but we'll see how we go.

I'm a little confused by the whole current feed thing. From what I can tell to get a channel to run at 0.35 amps you don't need to solder anything?

And can someone please give me advice/an example of a sketch to get one of the channels to dim a LED to get me started? Thanks.
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Standard LEDs run somewhere around 20mA, and many have a maximum DC current of 30mA, so you're likely to blow those up if you put 35mA through "normal" LEDs.
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I just tried hooking a single bog standard red LED up to it along with my multimeter and its pumping 12 volts (the supply voltage) through the LED. Do I need to put several LED's in paralel to draw the 350ma needed to make the chip realize there is load connected to it?
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Wiring LEDs in parallel doesn't work; they don't share current properly.

If you're worried about ruining your XM-L LEDs then maybe you could test with a generic brand first. 1W (350ma) white LEDs on a star can be found 50 cents a piece or less.

XM-L LEDs are spec'd up to 3000ma so testing with just 350ma (the default for the Ledsee board -- you don't need to solder anything) leaves plenty of room for error. The most important thing is to make sure you've got it mounted on a good heatsink and just make sure it doesn't get too hot. Just wire it up and test it by connecting a wire between the 5V output on the board and pin for the correct LED channel (pins 2 through 7).
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This shield uses the powtec PT4115 LED driver. It is directly connected to the Arduino PWM pins. As GrumpyMike said, the AnalogWrite function will do for PWM dimming. Having that said, however, that leaves to be desired. The PT4115 has a dimming ratio of 5000:1 easily enough for 12bit dimming but the Arduino pins only allow 8- bit, at least in the AnalogWrite function.

There are ways to get some of the pins to dim at 16 bit, but I am not sure if that will work for all 6 PWM pins.
If you use both shields on the same Arduino Mega ADK you'll still only be able to control 6 independent channels, not 12 as both shields will use the same 6 PWM pins.
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OK thanks for your help, I have the LED's on their own and the PCB boards to solder them too but I don't have the tools/expertise to solder them on as their tiny and surface mount. I'll have to take them to someone who has the tools/expertise and ask them to mount them
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