House Lighting, Gru gives the orders

Click a command. Gru shouts it, the right minion (a ULN2803A channel) yanks its zone to ground, and the lights come on. Same wiring as the build.

G G G G
GF · ×2 white 220 OUT1 · pin18 ground floor · off UP · ×3 white 220 OUT2 · pin17 upstairs · off EXT · ×5 white 220 OUT3 · pin16 exterior lights · off FIRE · ×1 RED 220 OUT4 · pin15 fireplace · off GRU = Arduino · the boss shouts PWM on D3 · D5 · D6 · D9 D3→IN1 D5→IN2 D6→IN3 D9→IN4 MINIONS! Await orders…
▬ zone wire (LED → OUT) ▬→ active order · ▬ ▬ idle · each minion sinks its zone to ground (ULN pin 9), see the pin map below
The actual pin map
ZoneGru says (Arduino)Minion ear (ULN in)Minion hand (ULN out)Lights
GF_INTD3IN1 · pin 1OUT1 · pin 182 white
UP_INTD5IN2 · pin 2OUT2 · pin 173 white
EXTD6IN3 · pin 3OUT3 · pin 165 white
FIRED9IN4 · pin 4OUT4 · pin 151 red

No 1kΩ base resistors (built into the ULN). Each LED: +5V → LED → 220Ω → OUTx. Same sketch, same scenes.