I am currently trying to power my 11x11 LED matrix, but the arduino uno that I'm using clearly doesn't give enough power to power all 121 LEDs. The maximum that I've tried was 44 LEDs, but anything more than that didn't work.
I am looking for a way to power the 121 LEDs externally using a LiPo battery or eventually using a wall power supply, but I haven't found a solution, since I am relatively new to the hardware scene.
Are you using a resistor on the data line and a large capacitor on the LED’s power supply input.
You should also apply power and ground at least at both ends of the strip and maybe in between. You might want to add another capacitor at the end.
However what is the current capability of your power supply?
You have a conceptual problem here - and are confusing people somewhat.
The Arduino UNO does not "power" anything - it has no power supply. The on-board regulator is not capable of supplying anything other than the processor itself. You appear to be connecting the LED strips through the UNO from the USB. There is a polyswitch on the board which will - sooner or later - shut down (everything!) if you draw much more than 500 mA. You need a fully regulated 5 V supply to connect to the LED strips and the 5 V pin on the UNO.
WS2812s take 60 mA each at maximum, so 121 will require 8 Amps - call it a 10 A supply.
When you do that, you need to wire the array properly. The 5 V and ground wires need to connect to every row (on each side) while the Data zig-zag wires connect only the successive rows. At the feed point, you need to attach the 1 mF capacitor. Using those jumper wires is inappropriate (and a bit of a waste - they are just for using in breadboards), you need to use thicker insulated wire stripped and soldered at each row (if you are careful, it does not need to be cut), no longer then the distance between rows so that it lies flat on the board. Those strips are not too long, but when they are longer, you need to have a parallel feed of the power to both ends.
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