WS2811 and 10W RGB LED?

[champagne]

I received my arduino kit 2 weeks ago and wanted to try a variant on the great LED example that came with my kit (https://learn.adafruit.com/adafruit-ard ... 3-rgb-leds) - So great, I have the LED changing color and fading!

I have a couple 10W RGB LEDs (FW is 6 to 7V or red and 9/10V for G et B) and I'd like to use it instead of the LED that comes in the kit.

Now for the silly questions from the newbie:
- the FW current for the LED is 9/10V - could I use the WS2811 to power the LED? (http://www.adafruit.com/datasheets/WS2811.pdf) - did I get this correctly that if I power the ws2811 from the arduino 5V and put the LED behind it it it could power the LED correctly? then PWM it through 1 port of the arduino and daisy chain them through pin 5? I would need to put a resistor I suppose before the RGB pins since output is 12V from the WS2811, right? Am I looking at this the right way?

- if I daisy chain more than a couple of these lights I suppose I will need an external power supply to accommodate I and the wattage necessary? could a Generic AC 110/220V to 5V DC 20A 100W power supply do the trick?

- if I just put some low Resistors as in the example to maintain current constant to the LED and power it w 5V from the arduino, wouldn't the light work but just not be very bright?

- I was looking at this example on how to drive 10W LEDs: http://www.instructables.com/id/Build-t ... n-Scanner/ I suppose the 16 Constant Current Regulators that gentleman is building act as the WS2811 but in my case 1 WS2811 will be nought to drive 1 RGB light and control it?

thanks in advance for any help/pointers you may have on this!

Xavier

[adafruit_support_bill]

The WS2811 can only supply a few milli-amps per channel. Not enough to drive a 10W emitter. What you need are some MOSFETs like the ones used in this tutorial:
https://learn.adafruit.com/rgb-led-strips/usage
http://www.adafruit.com/product/355

[champagne]

ah great - thanks a lot for the help. I suppose I can run several lights as well from the arduino using a Shift Register like the 74HC595 you carry? (https://www.adafruit.com/product/450) 3 of them would help me manage 8 lights? for the power source, if my arduino is connected through usb, can I use the 9V output to power the circuit? thanks again for the help!

[adafruit_support_bill]

Using a shift register you can have on/off control on each channel only. For full variable control of 8 RGB leds, you would need 24 channels of PWM. You could do that with 2 of these: https://www.adafruit.com/product/1411.

[champagne]

Thanks for the reply.

One last thing(hopefully): the LED FW current is 6 to 7V or red and 9/10V for G et B - could I use TLC5947 (https://learn.adafruit.com/tlc5947-tlc5 ... t/overview) and connect my 9V source to the TLC5947 and drive my LEDs that way? (the Adafruit 16-Channel 12-bit PWM/Servo Shield only takes in 5V right? which would not be enough current for the green and blue lights?

my final list for the project would then be (for powering 6 lights)
18 N-channel power MOSFET - 30V / 60A
1 Female DC Power adapter - 2.1mm jack to screw terminal block
some 12V 10A switching power supply (I did not see any on adafruit?)
1 TLC5947 LED driver

Ability to drive servos and LEDs would be neat, I could have 1 servo turn 1 of the arms of the light but I'll keep this for project #2 :-)

this is going to be an expensive light but should be fun! thanks again for the help.

X

[adafruit_support_bill]

could I use TLC5947

The 5947 cannot source enough current to drive a 10W led. The design is not well suited for driving the MOSFETs either.

the Adafruit 16-Channel 12-bit PWM/Servo Shield only takes in 5V right? which would not be enough current for the green and blue lights?

The PWM outputs only need to drive the MOSFETs. 5v is plenty for that.

We do not have a 12v/10A supply. They do exist. Or you could split the load across 2 12v/5A supplies: https://www.adafruit.com/products/352

[champagne]

ok, so just to make sure I got this correctly - in order to wire 1 RGB light:
- I use the 16-Channel 12-bit PWM pins 0,1 et 2 to connect to 3 MOSFETs
- Middle pin of Mosfet goes to 1 of the RGB inputs of the light
- power (+) side of light comes from my 12V/10A power supply - connect ground from power supply to arduino, arduino gets power from usb

did I get this correctly? thanks again!

[adafruit_support_bill]

That's right. Also:

PWM pins connect to the Gate (left pin) of the MOSFETs
Source (right pin) connects to Arduino ground.
Power supply ground connects to Arduino Ground. (i.e. all grounds connected together.)

[champagne]

k very cool, I'm doing this. Before I put my order in, any cables you can recommend to plug on the 16-Channel 12-bit PWM/Servo Shield pins so I don't have to solder cables individually? thanks again for the help!

[adafruit_support_bill]

These jumpers are pretty versatile. They come in a 20-conductor ribbon, but you can peel off as many as you need at a time to make multi-conductor jumpers.

[champagne]

k I put my order in yesterday! While reviewing the post on Adafruit 16-Channel 12-bit PWM and MOSFETs I was wondering if I needed to put some resistance before the MOSFET since the LEDs will be powered with an external 12V supply and the R needs 5-6V and G/B need 9V?

I looked at the 16 channel spec and it says each PWM output has a resistor for 200 ohms so I suppose U=RI if the tension needed for Red is 6V and we have 12-6=Rx0.35 (intensity for my led is 350mA) then that means I need R=20ohm ? did I get this right? is that why I don't need put any resistors on my setup? Each RGB will get the right amount of V through the MOSFET? Thanks!

[adafruit_support_bill]

The resistors on the PWM board apply only to the signal it is feeding to the MOSFET. They will not limit current to the LEDs. You can limit currnt to the LEDs n two ways: You can put resistors in series with the R, G and B channels of the leds. Or you can restrict the duty cycle of the PWM to keep the average current to less than the rated current for the LED.