Hello everyone, newbie here 
I want to build something using the WS2812B LED's. Which wire gauge should be used if you want to cut the LED's from a strip and connect them together again? Will 22 AWG suffice? I would like to use 300 LED's in total, so total power consumption is 60mAx300=18W at 5V, so I would at least need a 4A power supply.
Thanks!
300 led's at 60mA with 5V is NOT 18W. That's 18A!!! Or 90W.
22AWG is fine for the data lines. For the power (5V and GND) it's a wayyyyy to small if you want to connect them in a long string.
Tip would be, DON'T connect GND and 5V in a string alone but reconnect it to a thicker wire(12AWG+) every let's say, 30 led's. That thicker wire will run parallel to the line of leds. Or, wire it as a star topology.
septillion:
300 led's at 60mA with 5V is NOT 18W. That's 18A!!! Or 90W.22AWG is fine for the data lines. For the power (5V and GND) it's a wayyyyy to small if you want to connect them in a long string.
Tip would be, DON'T connect GND and 5V in a string alone but reconnect it to a thicker wire(12AWG+) every let's say, 30 led's. That thicker wire will run parallel to the line of leds. Or, wire it as a star topology.
Ah yeah, true. Miscalculation 
The thing is that I would like to build a matrix out of the LED's, could you maybe make a drawing about the wiring for let's say a 12x12 matrix, I don't completely understand it
With 281x, you do not make a "matrix", per se. You cut it into a bunch of strips and arrange them so the LEDs are spaced the way you want them to be, and connect the out of each strip to the in of the next strip - so it is still controlled as one long string. This also makes it convenient to connect the power rails of each strip to some good, thick wire at the ends of the strips, since all the ends will be close together.
"matrix" generally implies that you're multiplexing the LEDs by having each row and column tied together, so you can use 2 * sqrt(number of LEDs) pins to control it instead of (number of LEDs) pins. This means each LED has a duty cycle of at most 1/sqrt(n), so they are much dimmer than they otherwise would be. Now that WS281x's are so cheap and abundant, many applications where you'd use a matrix in the past can be done with addressable LEDs, and come out looking brighter, having full color, and much easier wiring.
[u]This page[/u] has a chart of wire gauges with maximum current ratings. If the wire-lengths are short you can use the "chassis" ratings. For longer runs where you might get a voltage-drop, use the "power transmission" ratings.
And, make sure your connectors are rated for the required current. Most of the heat & voltage drop usually happens at the terminations and that's what usually fails or burns-up.
DrAzzy:
With 281x, you do not make a "matrix", per se. You cut it into a bunch of strips and arrange them so the LEDs are spaced the way you want them to be, and connect the out of each strip to the in of the next strip - so it is still controlled as one long string. This also makes it convenient to connect the power rails of each strip to some good, thick wire at the ends of the strips, since all the ends will be close together."matrix" generally implies that you're multiplexing the LEDs by having each row and column tied together, so you can use 2 * sqrt(number of LEDs) pins to control it instead of (number of LEDs) pins. This means each LED has a duty cycle of at most 1/sqrt(n), so they are much dimmer than they otherwise would be. Now that WS281x's are so cheap and abundant, many applications where you'd use a matrix in the past can be done with addressable LEDs, and come out looking brighter, having full color, and much easier wiring.
Yes, that is what I am trying to do. Just connect the LEDs in series, but cut like this: CUT So I can space them properly.
What exactly do you mean with: "This also makes it convenient to connect the power rails of each strip to some good, thick wire at the ends of the strips, since all the ends will be close together." With each strip you mean every individual LED?
I mean, when you cut the strip, if you're sticking each cut piece of strip in a rectangular pattern, all the ends will be along two edges, ie, physically relatively close, so it's particularly easy to connect them to a thicker wire for power and ground.
DVDdoug:
[u]This page[/u] has a chart of wire gauges with maximum current ratings. If the wire-lengths are short you can use the "chassis" ratings. For longer runs where you might get a voltage-drop, use the "power transmission" ratings.And, make sure your connectors are rated for the required current. Most of the heat & voltage drop usually happens at the terminations and that's what usually fails or burns-up.
Thanks for the link! So if for example I use 144 LEDs in a grid of 12x12 with let's say 2 cm spacing, i.e. wire length between each led, then a 21(Not so common i think)/20 AWG wire would work, as it's rated at around 9/11A and the LEDs draw 8.64A at most at full brightness. Please correct me if I'm wrong
Also, should I use an even smaller wire gauge for the connection between the power supply and the first LED? I think the length of that wire will be at most 20cm/7.87inch.
