I'm working on project that involves 100 white and 100 RGB leds, controlled with 25 TLC5940.
I've managed to connect three TLCs to Arduino MEGAv3 and so far so good. I've found out that I have to add 0.1uF capacitors( ceramic, but I can only get film) between TLCs VCC and GND to smooth out voltage drops and 1uF / 100uF caps along the positive, negative rails. (to not burn down TLCs) I'm using these LEDs: RGB and WHITE
So, from TLC5940 basic use example, i calculated that i have to use 1,5kohm resistor on each TLC to provide 26,04mA per LED channel. So at full on, all this should pull 26.04x400=10.416Amps! As this is going to be freestanding installation I'm thinking on using 12v 105Ah car battery. (not connected to car) with this buck converter DC/DC 12V-5V 15A 75w
So the questions, that I haven't found answers to, are:
- How to calculate resistors for TLCs? Or are there not needed any..?
- And how to calculate resistors for LED? It's stated I = 39.06/R(in ohms) (i don't know why U is 39,06..) U = (Vc-Vled)/ILed = (5-3,4)/0,03 = 53ohm ?
- How to protect TLCs from any possible overheating that i'm not aware of ?
- Are my LED mA calculations correct ? as i measured with single led turned on, between arduino 5V pin and breadboard it shown ~36mA on multimeter. I have attached sketch below, it's only showing two TLCs, but this wiring will continue as shown.
UPDATE: This is my scheme as it is now on breadboard. I went with MeanWell 12->5V converter after consultations in arduino forum. I cannot take risks of running out of voltage because of voltage drop in system. Changed my white LEDs to more efficient model. Added SN74HC04N inverters for signal strength. I hope scheme is somewhat understandable.. It actually works as is and I plan to start soldering this to veroboards soon. There are definitely improvements to be made that i'm not aware of and maybe someone can point out some?