der_wille_zur_macht
Team RC
Yes, you can do that, as long as you understand the implications of running parallel strings. The strings MUST have the same voltage drop, else you will have issues. Ensuring the strings have the same drop is a two step process. First, build them from the same model/bin of LEDs, or equal numbers of different LEDs (i.e. you CAN NOT have one string of royal blue XR-E and another of cool white XR-E, but you can have two strings with 4 each). This is because different LEDs have different specified Vfs under different conditions. Second, once you have built your strings, you MUST test them to ensure they actually do have equivalent voltage drops. If they do, you're all set. If they don't, you have to swap LEDs around until they do. LEDs can have significant variation in Vf from the specified value (the manufacturers acknowledge this, it's not a conspiracy). You can determine if your strings are balanced by putting a 1 ohm resistor inline with each string and measuring voltage drop across each resistor (while running your LEDs at a safe low voltage).
Besides balancing the strings, you need to protect them from a fault - if an LED in one string fails open, the other string will instantly get twice the current you designed it for, which can obviously be bad for the LEDs in that string - the most common method of protection is installing a fuse inline with each string, rated above the designed current for that string but below the value it would get if the other string failed.
