the resistors and fuses are simple once you know why you are putting them in and undersatnd whats happening on a parallel string.
ill try to explain it.
most of the simple designs you see are one driver per 12 LEDs
These are usually powered by something like the meanwell LPC-35-700
This driver puts out up to 48V and .700amps
the LEDs are rated to have about 3.5 volts each and .700 amps per series.
12LEDS * 3.5ea = 42V. The driver above will adjust itself down to 42v
so the above driver can only handle one series (.700amps) and 12 LEDs (48v).
Now lets say you got a big bad driver that does 2.1amps and 48V
So now you can only still have series of 12 LEDs (48v). But since you have 2.1amps you need to balance that out between 3 series of 12 LEDs which gives you .700 amps per series.
The reason you start needing resistors and fuses is to be "safe"
So, if for watever reason one of those 3 series decides to stop, and other two keep running, you are dividing 2.1amps between 2 series instead of 1! Thats 1.050amps per series. If the LEDs cant handle it, boom goes the LEDs. This is why you put a 1amp fuse in before each series. As soon as one series goes, the 1amp fuse blows and your LEDs are safe.
So what is the resistor for?
Well for you to measure the amperage on each series you need to un-solder and put a multimeter inline with the leds. Well of course this sucks. If you put a 1ohm resistor at the beginning of each LED series then you just measure across the resistor while its inline and it will tell you the amperage.
From my understanding the amperage can vary per series so you want to switch LEDs out and get them as close as you can to each other. Over time it can change also, so having the resistors in there for quick tests works great.
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