I want to control 61 SMD 3528 RGB LEDs (KT-SMD3528-RGB) with 3 arduino Micro's 3 PWM pins. I learned from reading up that I'll have to use 3 NPN Transistors to control RGB LEDs and external power source.
So I decided to go with external 5V power supply to power up those LEDs and since I have 61 of them and I'm noob in calculating power requirements I would like to ask a question of how much amperage draw I'll need a power supply
I have 3528 RGB led which draws roughly 25mA on each channel, meaning I'll need 25*61 = 1.5 Amp to power up each channel. Does this mean I'll need 3*1.5=4.5 Amp 5V power supply?
Also regarding resistors as I understand some channels have more Vd than others (I haven't measured them yet as I'm still waiting for shipment to arrive) but according to sellers, specs are 1.8 to 3.5 Vd on those SMD LEDs. So for example to calculate resistor I need for 1.8 Vd I need to do math like this (5-1.8)/0.025 = 128 meaning I'll need at least 128 Ohm resistor for each led channel. Is my logic correct?
Also regarding NPN transistor for each channel I need a transistor that could sustain at least 1.5 Amp is this also correct?