Are all your LEDs the same color? What color?
I would use two power supplies - one for the Arduino one
for the LEDs.
I would use a 24V supply for the LEDs. Series up LEDs until the sum
of the Vf's is within 2 or 3 volts of 24V (for white LEDs this
is usually 7). Use a FET to turn the LEDs on and a resistor
to limit current. This will reduce your current my a factor
of 7. Parallel the LED strings as required.
If you wire all the LEDs in parallel I would get an adjustable
supply for the LED voltage. Adjust the supply so it is just above
the maximum Vf spec of the LED. Use a series resistor to limit
current. Your maximum current hasn't changed but your
efficiency is improved.
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