andrewfowler:
dont think i explained my self very well
Try using grammar and punctuation. Reading your posts makes me feel out-of-breath!
I think you are saying: 16 LEDs in total, in 4 groups of 4. The LEDs in each group behave identically.
Nano does have enough pins for this. You don't need mega, or more than one nano.
Two options:
- Use more nano pins for the extra LEDs. You can use the analog pins A0 to A5 as digital outputs, but not for fading. Where you have digitalWrite() or analogWrite() in your sketch, just duplicate those lines and put in the new pin numbers.
- Use just the 4 pins you are using now, with no code changes. Use 4 transistors (e.g. bc337) or a ULN2003 or ULN2803 chip to allow you to run 4 LEDs off a single pin.
If you use transistors, connect the base to the Nano pin with a 4K7 resistor. Not needed with the ULN chips.
You must use a series resistor for each led, so 16 series resistors in total. LEDs connected in parallel cannot share the same series resistor.