Hi,
I'm working on a project to connect a 30W RGB Led to Arduino and manipulate it with MAX with maxuino.
in the photo you can see the connection that i'm using. The Mosfet is an IRF-Z44
The problem is with the PWM.
I've look in different post and themes on the web and I'm still blocked... With a normal rgb small led everything is ok, but when i connect the 30W rgb, either the arduino sketch with a potentiometre or the pwm output from maxuino works just as ON/OFF and not as PWM...
You need a [u]constant current power supply/driver[/u]. There are dimmable constant current (controlled current) power supplies that use 0-10VDC or 10V PWM to control the dimming circuit.
With "regular little" LEDs you can use a resistor to control/limit the current but with high power LEDs a switchmode supply is used because otherwise you'd need a big power resistor and that's inefficient and the resistor gets hot.
With your existing circuit, you have no current limiting/control and you are in danger of frying the LED, your power supply, or your MOSFETs.
Thanks for your answer...
So, there is something that i don't understand... These means that i can't use high power led via Arduino and so... via MAX MSP?
It means you can't do it with the circuit that you have. You can do it if you use a proper circuit that implements a dimmable constant current control for your LEDs.
No not for one LED, this is designed to dim a string of LEDs in series. The minimum output voltage is too high for just one.
Anf if is these, how can i control the three color in a separate way? Ther is just one 0-10V control input??
You would have to have three of these, one each for the red, green, & blue component. But your LED has a common anode so you can't put more diodes in series.
As that LED is a common anode design you need a constant current sink, not a source.
You need three of these circuits, one for each colour LED. You can make or buy things like this.
Search for :-
300mA constant current sink
As there are multiple LEDs in series inside this LED you will need a supply of 33V, or over. This means that the constant current for the red LEDs has to burn off more power than the others so that one will need a good heat sink.
If you do it will be a waste of money. That device is a constant current SOURCE not as told to you a constant current SINK.
That device would have worked if you had a common cathode LED but you have a common anode LED.
Then connect the common anode of the led to the Led+ of eache driver and each color to each led
Now, i'm preparing the circuit, but there is something that i don't understand, in the Datasheet they said the the i've to connect the LX pin to the Anode of the Led. So I've a common anode led, where i connect the Cathode of each color?
in the Datasheet they said the the i've to connect the LX pin to the Anode of the Led.
Well not according to the diagram on page 1 of the data sheet. That shows LX going to the inductor and the anode of a flyback diode. It shows the Anode connected to the supply voltage and the cathode to the other side of the inductor.
