I have 29 RGB LEDs connected in parallel and will control them with PWM.
They can handle 20 mA per color. I was planning to supply them with 5V and measured the voltage drop per block at 20x29 = 580mA input 5V.
- Blue drops 3.06V so resistor needed: 3.9 ohm
- Red drops 2.15V so resistor needed: 5.6 ohm
- Green drops 2.95 so resistor needed: 3.9 ohm
Combined resistance: 1.45 ohm
The cable is a common UTP CAT6 cable I merged the ends so 8m of wire and measured with 2 multimeters and it's 3 Ω. This is the problem. The total resistance is 4.45 ohm and that is max 1123 mA instead of the desired 1740 mA
Can I do a 9V supply to get the current with adjusted resistor values or will it hurt the LEDs?
They won't be running at ful power all the time, PWM will adjust the colors so power dissipation should not be an issue.
Unfortunately I can't find the datasheet. Part number EVERLIGHT EVL-504-90-CA