Hi,
I have an arduino UNO R3 and a RGB strip. I want to controle the RGBs but they have 3 GND and 1 5V+. I am going to use transistors but i want to program my RGBs, so they can fade from blue to white. I for that I'm gona need to output 0.5 A, 0,6 A and 0,7 A to make dade effect (This output si going in to transistors) . As I was researching the arduino outputs 0,2 A (200mA). How do I program my arduino to do that?
Thanks if you rade all this. I will be happy if someone can help me.
First, the Arduino is not a power supply, so you are right to drive the transistors with the Arduino GPIO pins. You do not power the strip from the Arduino. The strip should have its own power source.
You are wrong that the RGB strip controlled by current. You can't "program" any Arduino to output a specific current.
You control the RGB strip with PWM. Look at the example sketch in the IDE called "fade". This will give you a basic understanding of PWM.
Post a data sheet for the LED strip.
That's what your transistors (or MOSFETs) are for. 
To "boost" the voltage and/or current. It just takes a small current (or no current into a MOSFET) to control the main-current through the transistor/MOSFET and the load (the LED).
Here is a MOSFET driver circuit. Of course, you'd need 3 of them. It's shown driving a motor with a 12V supply but it can also be used with a 5V and a 5V LED strip. Since you don't have an inductive load you can leave out the diode.
A regular bipolar transistor can be used in a similar (but not identical) circuit.
Dimming is normally done with PWM (see the Fade Example). PWM pulses on & off faster than your eye can see which makes the LED appear to dim (and it's off part-time the average voltage & current is reduced).
The driver circuit will "pass-through" the PWM and it will work just like a regular little LED without the driver.
Just double checking…
Are your LED strips ‘smart LEDs’, or discrete RGB LEDs?
The way you drive them is completely different.
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