LED Driver + Mosfet / Linear Led?

Hello,

I need some help on what to do, or if there are any other options or parts that I can easily implement.

I have a 100W Led chip,

My power supply is rated 12V 120W, and I have added a booster to get 30V, less than 100W.

Currently, I have arduino mega, connected Pwm pins to mosfet, which controls the led chip. My input comes from a potentiometer, which is mapped as pwm=map(0,1023,0,255).

The problem was, the dimming on the led was steppy, it would go in steps. I tried different mapping, increase and decreasing number for bottom half and top half, etc. but no luck.

I also tried, doing 16bit pwm, had very less effect. but better i guess.

My question is:

  1. Could anyone tell me how to calibrate a led curve? or should I try everynumber 0-255, then try different arrays and work with that?

  2. I read that leds are dimmed using constant current dim method.
    So, would connecting a led driver to the mosfet, have better control?

Led driver

  1. I have tried, using a low pass filter circuit. that didn't work either. Should a DAC which converts pwm to analog voltage be better option?

If you need more information, please let me know.

Hi,
How are you powering your LED?
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
Can yu post a picture of your project so we can see your component layout.

LED like that really needs a current controlled driver, 100W.

If you are using 12V supply you need it to be able to supply…

P = V * I

SO I = P / V

I= 100 / 12 = 8.33A

The sparkfun device does not have the current carrying capacity.

Have you googled?.. arduino LED driver

This may help… Loading...

Tom… :slight_smile:

You can't properly drive an LED with a constant voltage and a MOSFET. LEDs are driven from a constant current source. You can buy a [u]constant current LED supply[/u] or you can build one, but they are not easy to build. (A regular little LED is current-controlled by a resistor. But, you probably don't want to use a ~100W resistor in series with your 100W LED.)

The industry standard for dimming control is 0-10VDC or 10V PWM, so if you by a dimmable power supply you'll still need a small transistor or MOSFET (and an ~10V power supply) to "boost" the Arduino's output voltage.

  1. Could anyone tell me how to calibrate a led curve? or should I try everynumber 0-255, then try different arrays and work with that?

The "curve" probably isn't the issue. When step from 1 to 2, that's a 100% increase, and you might notice the change. A step from 254 to 255 is less than 1/2% and you probably won't see it.

  1. I have tried, using a low pass filter circuit. that didn't work either. Should a DAC which converts pwm to analog voltage be better option?

Analog into your MOSFET won't work because if the MOSFET is "half-on" it will overheat. 16-bit analog or 16-bit PWM into a constant-current supply would give you more resolution. (With 16-bits you have 256 times as many steps... More than 60,000 steps.)

P.S.
The LED also needs a heatsink!

This 100watt COB LED (10101watt LED) needs ~33-35volt, with a constant current of 3Amp.

Not sure what you were thinking there (300mA).

"My power supply is rated 12V 120W, and I have added a booster to get 30V, less than 100W".
Needs to be 36volt minimum for the LED and the losses in the driver, and capable of 3Amp.

"Currently, I have arduino mega, connected Pwm pins to mosfet, which controls the led chip."
A "LED chip" (like the ones from Sparkfun) already have the switching circuitry onboard.
Adding a mosfet is wrong.

"The LED also needs a heatsink!"
Yep, a beefy CPU cooler with fan is needed for a 100watt LED.
Leo..