Hi:
I am new here, I just want to share the LED array that I did today. Each column of 4 LEDs are in series with a 220 Ohm resistor, the columns are in parallel between each other. I use a 9V power supply and a small switch.
It has only 23 Infrared LEDs, and I use one blue LED as a pilot to know when it is working. There is plenty of space to add more LEDs in the future.