choosing a transistor

Hi all !

(this is my first post here)

I've bought an 5m RGB led strip and an Arduino duemilanove to control it.

It's not clearly described if it's a common anode/cathode :frowning:
Maybe "positive light" is a hint...

LED quantity: 5 M in a roll of 300 LEDs ( SMD 5050 )

Type: Epoxy Waterproof positive light

Power: 72 W

Voltage: DC 12V

What I would like to do is to decorate my kitchen with 2 ~60cm chunks (approx 60 leds each).
I'll use PWM and some transistors to control leds.

I've done calculations:

72W / 12 V = 6A (for the whole strip)
6A / 300 led = 0.02 A/led = 20mA/led
66 led * 20mA = 1.32 A

I've saw on other threads that someone used an ULN2003A (which will be good as there are 7 transistors inside) but it seems to handle only 500mA :cry:

Could someone help me to find the good transistor :

  • if I want to control the whole strip (6A)
  • if I want to control 2 chunks of 60cm

Best Regards

Link to the led strip : Discount China Wholesale 5050 SMD RGB LED Strip Wateproof Flexible 300 LEDs 5M + Remote Controller [LS-5050RGB5300A]- US$49.99 - SatisLED Store,Wholesale China LED Lamps, Power LED, LED Strips, LED Floodlights, LED Tubes, LED Spotlights, LED Downlights, LED Aquarium Light LED High Bay Lights, LED Contronller, LED Driver

(sorry the security prevent me posting a link on my first post ! >:()

how bout this

runs about 70 cents on digikey
(youll need 3 of them)

looks like that one is hard to get in single quantities, try this


Thanks for your quick replies !

you're right IRL530N seems to be fine. I'll order 3 of them.

Do I have to put resistors between the arduino and the transistors bases ?


you can put a 200 or so ohm one if you want to be safe. not absolutely necessary, but ymmv

equipment ordered. I'll return when I received everything.
Regards !

good luck! come back if it works, im curious to know


I've received my arduino, IRL530N, solderless breadboard, and mostly time but but I'll go crazy !

I can't get the transistor working! Maybe I'm missing something.

I've found in the IRL530N datasheet that pin are like this:

So as a test I've connected:

  • arduino pin 13 to "1- GATE"
  • "2- DRAIN" to arduino pin GND
  • arduino Power 5v to a led
  • second led leg to "3- SOURCE"

Using the blink test at "",
the led should be blinking, but it's still on!

I've changed the transitor, put it on the other side, tested all combinaisons. Done plenty of other tests. But never comes to get it respond like I'm waiting.

Could someone explain me what I'm doing wrong.

  1. Missing gate resistor. Probably not good for the transistor.

MOSFETS don't really require gate resistor as the gate is insulated from the source and drain terminals. Sometimes a gate pull down resistor is required in case the signal driving the gate is removed causing a float condition.

I don't think the following hookup is right

Connect the Arduino, D and LED power's ground together.
So as a test I've connected:

  • arduino pin 13 to "1- GATE"
  • "2- DRAIN" to arduino pin GND
  • arduino Power 5v to a led
  • second led leg to "3- SOURCE"

This shows three pins

Gate goes to digital or pwm out on Arduino. It's a logic level input device no other stuff needed.

+12V to the positive on the LED strip

Source to the - on the LED strip

Drain goes to ground

You should have the Arduino powered either by USB or it's power supply.

The ground of the Arduino must be connected to the ground of the +12V supply. I'd suggest the power supply be better than 6A by 25 percent so 7.5A just to keep it from maxing out.

I need to learn Fritzing to draw this stuff.

I've changed this from source to sink, sorry if you got one of the revisions I need to preview better.

You should have a heatsink for that. At max current it may get toasty. You can easily hack one together and use left over heat sink grease.
For precision this can help but it has math Thermal resistance - Wikipedia

MOSFETS don't really require gate resistor as the gate is insulated from the source and drain terminals.

True but a off gate looks like an uncharged capacitor so you might want to add a 100R series resistor to protect the arduino pin from the brief over current that occurs when the FET being switched on.

thanks for your responses. but it still doesn't works.

Here are the pictures of what am I doing. Maybe you'll find where is the problem... The led should be blinking, but it's fixed ON.

R1 for led protect is a Red/Red/Red 2.2k
R2 for Gate is a Brown/Black/Red 1k (also tested with Brown/Black/Brown 100)

Thanks for the advice about the power supply :wink: I'll keep that in mind.
For now, I'll just forget 12V, and focus on 5V and get this MOS working.


Ha ! I finaly get it working.

As Richard said, I've Mixed up Source/Drain.

Found that info elsewhere too:

When using a MOSFET it is important to be clear about which pin is the drain (D), which is the gate (G) (the equivalent pin is labelled 'Input' in the VNP10N06) and which is the source (S). The drain in connected to the load, the gate to the input signal and the source to 0V.

Thanks to all, I can now go further in my project :slight_smile: :slight_smile:

W00T, when done post pictures here. :slight_smile:


this is my "final testing stage" before realization !

YouTube Video:

This is a test application for controlling RGB strip led with Arduino.
It used 2 Arduino:
* one for controlling strip led with TLC5941 so I can control "as many strip chunk as I want".
* Second for decoding IR messages.
(The two Arduino libraries were incompatible on the same chip)
Communication between the cards is done by connecting 5 digital output pin from IR card to the 5 analog (but digital mode) of the "master" card. +2 other pins for communication ack. I send binaries data, each code corresponding to one touch from the remote.
I'll be using this to do lightning in my stairs ! :slight_smile: But this will be another video !

I'll post something on the Arduino Projects Page when completely done !