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[Reply #15 on:]

This is what i have build, and all is working great.
You can control the ledstrips with the shiftpwm library to control brightness and colors with PWM

[Reply #16 on:]

but what happens to PIN 9?

Nothing leave it disconnected.

This pin is designed to be used with motors that generate a back EMF, by connecting this to the +ve supply will put a reverse diode across the load. You do not have to connect it to anything.

I think I understand it now, just a quick check to make sure I'll be doing it right:


Now when I look at this scheme, I find it a bit useless indeed to use there transistors to controll one single channel. What is your advice, replacing them with 3 BD679?

[Reply #17 on:]

Well you still have pin 9 connected.
Yes a single power Darlington would be good, but a logic level FET would be better as you will loose less voltage across it. See what your local supplier has in terms of logic level FETs.

[Reply #18 on:]

I made some RGB+white LED eyes for the house for halloween.. I would recommend using discrete transistors rather than the ULN arrays because you are going to be able to sink a lot more current with discrete power transistors. I would suggest TIP120, they are Darlington NPN and can handle quite a lot of current.  For an LED project I am working on at the moment, I am using home made darlington pairs, using 2n2222 for the control transistor and TIP41c for the power transistor.  Only draws a couple milliamps for switching and can sink up to 6A.

Is there current limiting built into the strips you bought?

[Reply #19 on:]

Well you still have pin 9 connected.

I did solder it all up and it works perfectly fine to control the LED strip using Arduino, thanks!
What would I need to adjust the brightness of this strip?

Do things like a PWM powered resitor exist, or would another ULN2003 on the 12V do the job?

[Reply #20 on:]

Do things like a PWM powered resitor exist,

No.
Just feed the ULN2003s with PWM outputs, in place of what you have and use analogWrite to set the brightness