Lighting Lots of 1.2v Bulbs...or Bright LEDs

Projects General Guidance
3

There are 20 pins, but still not enough, 0-13 and the analog inputs A0-A5 can function the same as the digital pins as well.

Several choices here:

  1. Use shift registers to provide more outputs. 74HC595 shift registers have 8 outputs and can be cascaded, so four would be needed.

  2. Use a multiplexing chip like the MAX7219 or MAX7221.

  3. Multiplex the lamps directly with the Arduino.

(1) Will be the simplest code, but lots of wires, (3) Will be the least complicated electrically, but the code will be more difficult, (2) is somewhere in between.

FWIW, if it were me, my preference would be LEDs over 1.2V incandescent bulbs. Current drawn from Arduino pins should be limited to 20mA.