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Topic: RGB Strip to Arduino Uno -- Red still on? (Read 2709 times) previous topic - next topic


Hello all,

I am doing a project on an Arduino Uno, connecting a 15.4 ft. RGB LED Strip. (Specifically this onehttp://www.amazon.com/gp/product/B007X968RA/ref=oh_details_o00_s00_i00)

Powering the Arduino, I have a 12 V/ 3A power converter that came with the LED's (so it has to work, right :))

For Pins...
Vin = 12 V of LED Strip
PWM #9: Blue LED's
PWM #10 Red LED's
PWM #11 Green LED's

However, my problem is that when everything is connected, the Red LED's are always slightly on, no matter where plugged into.. However, they do not do this when plugged into the power supply that came with LED's, only when plugged into the board.

Also, everything also sees a bit dim. If i run a wire from the "green" led connection to the GND, it get's the normal brightness.

Any idea how to fix this??

I appreciate all help...

PS: I know that the LED strips with the 2801 are a lot easier, but I want to get this to work first. Again, thanks for all help :D


Have you any transistors in that setup? You can't connect an arduino PWM pin directly to the cathodes as it will have 12V across the pins when it is off.


No I don't. I guess that could be the problem.

How come though only the red LED's would be on, and no other color??

Sorry for all the questions, I'm studying CSE, not EE :D :D


No I don't. I guess that could be the problem.

You are in great danger of damaging your arduino, with both over current and over voltage.
You should always take less than 40mA into or out of a pin otherwise damage will occur.
You should never put a voltage greater than the supply voltage on a chip's output.

How come though only the red LED's would be on, and no other color??

Because red LEDs have a lower forward voltage so it takes less voltage to turn them on. So when you think they are off they are not there is 12-5V across them, just enough for the red but not enough for the other colours.

Get you circuit right before you completely destroy your arduino.


Thank you very, very much for your help. This makes complete sense now.

I am going to follow what they say here http://learn.adafruit.com/rgb-led-strips/usage.

Again, thanks for the help. I'll let you know how it goes :.


Thank you so much!! That's exactly what it was!!!

When My project is complete, I'll be sure to show!


There is a mistake on the Adafruit page,  they say
You can use any power NPN or N-Channel MOSFET,
but you must use one that has" logic level" gate voltage ( will switch on with 5v from the Arduino )

If you use a normal MOSFET, it may not turn fully on with 5 volts on its gate, and will act as a resistor and get hot.
45 years of editing projects with a knife and soldering iron, then I found Arduino !

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