Driving several 10W LEDs with PWM

Hello everyone!
Now I'm working on a project that uses Arduino to show water conditions and people's movement with using two 10W high power LEDs. Each LED can change color simultaneously with the water condition and change brightness individually with people's movement.
Here is the link of the LED I got from ebay:

Some data of the LED:
voltage max. red---6.6V green---9.3V blue---9.6V
current max. 330mA

To be honest I'm a totally beginner of Arduino and do not have much knowledge of electric components or circuits. So I tried to do some research and finally found a tutorial,then followed the tutorial to build up a circuit.

Here is the tutorial:

Here is the schematic of my circuit, red letters show the components I use:

P.S.if you can't see the picture, here are my components:

Arduino UNO
R1: 10K
R2: 1.8 Ohm 0.25W
Q1: 2N2222A
V+: DC12V

the schematic is exactly the same as the one in tutorial.

For each color of the LED, I built such a circuit and provide it with a 12V power supply. That means each LED connects to 3 this kind of circuits and each color have their own 12V power supply respectively.

But finally my prototype didn't work nice. it just worked for several minutes as what I want it to do but then suddenly it stopped working. During most of the time the LEDs didn't light up at all. sometimes they lighted up but totally out of control. meanwhile, all the sensors seemed to stop working because I couldn't receive any data in serial monitor anymore.

Actually I'm quite confused now because I don't know which part caused the problem. I think maybe there is something wrong in the circuit. So I have some questions as following:

  1. Are the IRFZ44N MOSFET and 2N2222A suitable for this circuit? if not, what kind of MOSFET can I use for this circuit?
  2. Do I use too many power supply? Is it better to provide each LED 12V power(connect each color in parallel)instead of each color? I remember I read from somewhere that it might cause unstable voltage if connect each color in parallel. But I'm not sure whether it's correct.

I'm sorry that I'm not sure if I explained everything clearly... :confused: Any help from you is greatly appreciated! Thank you all so much! :slight_smile:

You should use just one power supply for all three circuits. if it can provide the current. In fact with a common anode you were in effect shorting out power supplies together and that is a bad thing.

You should also have a large capacitor, something like 1500uF across the power supplie's output.

The IRFZ44N MOSFET is not a logic level FET and this probably over heated.

But the big problem is that resistor in the circuit. That has a value of 0.82R which means that you have to have a current of 850mA to begin to regulate. Your LED needs only 300mA so this is where you fried it. You need that resistor to be 2.3R

That circuit was designed for a single 10W LED and you have an LED module with three LEDs in series, so it takes three times less current than a single LED, although it take three times the forward voltage drop you have that in spades with 12 Volts.

I'm sorry that I'm not sure if I explained everything clearly

No that was fine. I wish others supplied such relevant information. It allows a quick resolution, rather than having to drag information out of a poster. Well done. :slight_smile:

Thank you for your responding! :slight_smile: :slight_smile:
Actually I cut the common anode down before I put the LED into the circuit :wink:

Here are still some questions :o I don't really understand what's the capacitor for, is it for making the voltage stable? I'm also not quite clear about how to connect it with the battery, do I need to connect one side of the capacitor to the positive side of the battery, and the other side to GND?

I also find MOSFETs and capacitors as you suggested in ebay, I'm not sure that are they suitable for my circuit? here are the links:



Thank you again for your help!!! :slight_smile: :slight_smile:

I don’t really understand what’s the capacitor for, is it for making the voltage stable?

Yes it is for bulk decoupling:- De-coupling

do I need to connect one side of the capacitor to the positive side of the battery, and the other side to GND?

That is what I said wasn’t it?

Yes those parts will do. The capacitor is 16V maximum and while the maximum voltage you have is 12V, it would be better if you used a 24V or higher rated capacitor.

OK! I'll try them. Thank you so much!! :slight_smile: :slight_smile: :slight_smile: