Hello,
I recently bought an addressable LED chain but my problem is that I need about 3M and according to my calculation the LEDs need about 10,8 A which the Arduino can't deliver but it's just as hard to find a power supply that can be placed somewhere unnoticed. That's why my question is who is the best solution for this? I've already tried to control all 300 LEDs with 1 colour because they need less current, but I wasn't very successful because the chain went out after about 120 LEDs, so a tip on how to fix this would be nice too.
Rule #1 A power supply the Arduino is NOT!
Use a seperate power supply for the LEDs be sure it will supply your 10.8A or greater at the correct voltage. You must connect the grounds together but the positive of the power supply can be used for the LEDs only or other things if wanted. Posting a link to "Technical" information on the device would be much more informative than just listing a few features. It looks like that came from a sales site such as azon.
If you are using something like a WS2812 string you need to input 5V about every 100 LEDs. The traces on the flex board they are attached to have enough resistance that after 100-150 LEDs there is enough voltage drop they cannot fully power on the LED.
And, rather than end-feeding a string, make sure you feed your string from the center, as that way half the current flows in each direction from the connection point, reducing the voltage drop at the ends.
This is a detail that's almost always omitted by Utub and other tutorials, showing end-connection for simplicity.
That may not be enough. Adafruit recommends power every meter (similar to oldcurmudgeon's recommendation.)
If you have this problem, the LEDs will be dim (or off) as you get farther from the power supply but the LEDs closest to the power supply will work fine. (Assuming it's powered from the same end as the data-input pin.)
300 x 20mA (one color) = 6 Amps. 300 x 60mA (all 3 colors) = 18A.
The current requirements "are what they are". Sometimes you can "cheat" on the power supply if there is never a case where all LEDs are full-brightness white at the same time.
When you dim the LEDs it gets a bit tricky because you are lowering the average current but it's PWM so you aren't lowering the peak current. The power supply will be less-stressed when you dim but you can't make any useful calculations.
Assuming this isn't a software problem, if the whole chain went-out, that means your power supply can't supply the required current and the voltage is dropping. Do you have a multimeter to measure the voltage?
So i could usw the full lenght but i must connect every meter to the power supply and when i do that i will still need up to a 18A power supply to power up the full lenght (5m) of the strip is that correct?
Or could i use every meter a new supply with a lower current output?
Without precautions, that would mean that you have power supplies in parallel which is not a good idea.
In that case you will have to cut the Vcc track at the point where you inject the power. Like cutting the strip and joining GND and data again and Vcc (and GND) for each piece coming from a different power supply.