Bench Reference · Rev B · discrete-driver

House, Lighting Wiring Reference

4 switched zones · plain warm-white LEDs · ULN2803A low-side driver · cordless 5V.

Controller

Arduino Nano

Driver

ULN2803A · 8-ch

Power

USB bank · 5V

Outputs

D3 D5 D6 D9 · PWM

Sketch

townhouse_lights.ino

Series R

220Ω / LED

System schematic

Nano drives ULN inputs; ULN sinks each zone to ground

Signal (slate) = Nano PWM → ULN input. +5V red, GND black. The ULN pulls each zone's return to ground on command; the LED current never touches an Arduino pin.

Zone loop detail, how LEDs attach

Repeat per zone · add LEDs anywhere on the loop

Every fixture in a zone shares two wires: +5V and the zone's return to its ULN output. Wire an LED like this and drop it anywhere on the loop, no order, no polarity chain to keep straight beyond each LED's own + (anode) toward 5V.

Anode (+, longer leg) → +5V rail
Cathode (−, flat side) → 220Ω → zone return
One resistor per LED, keeps brightness even if one fails

BRIGHTNESS KNOB, start at 220Ω. Too dim? drop toward 150Ω. Too bright? the sketch's per-zone level also trims it in software. Dollhouse rooms read best low.

Output map

Zone	Arduino	ULN in	ULN out (pin)	Fixtures	Control
GF_INT	D3 · PWM	IN1	OUT1 · pin18	living + kitchen ceilings	dim
UP_INT	D5 · PWM	IN2	OUT2 · pin17	2× bedroom ceiling, attic	dim
EXT	D6 · PWM	IN3	OUT3 · pin16	porch A/B, entry, deck, balcony	dim
FIRE	D9 · PWM	IN4	OUT4 · pin15	hearth	flicker

ULN2803A: GND = pin 9. COM (pin 10) unused for LEDs. Inputs IN1–8 = pins 1–8; outputs OUT1–8 = pins 18–11.

Fixture schedule

Fixture	Zone	Install at
Porch light A	EXT	Pic 8–9
Porch light B	EXT	Pic 8–9
Front-door entry	EXT	Pic 8–9
Side deck / wing	EXT	Pic 8–9
Fireplace / hearth	FIRE	Pic 10
GF living ceiling	GF_INT	Pic 11 ✦
GF kitchen ceiling	GF_INT	Pic 11 ✦
Balcony wall light	EXT	Pic 12–13
2F bedroom ceiling	UP_INT	Pic 14 ✦
2F bedroom ceiling	UP_INT	Pic 14 ✦
Attic ceiling	UP_INT	Pic 16–17
Spare, eave / yard	,	any

SCENES, button on D2 cycles; auto-fades dark after 20 min idle.

Evening→All On→Night→Off

Build-order checklist

Pic 5, base closingMount Nano + ULN driver board + power bank + master switch in the crawlspace. Run a 2-wire loop (+5V + return) for each zone up into the house.
Pic 8–9, GF wallsWire the 4 EXT fixtures (porch A/B, entry, deck) onto the EXT loop through pre-drilled holes.
Pic 10, chimney baseDrop the FIRE hearth LED into the chimney.
Pic 11, GF ceiling✦ wire before glue Glue the 2 GF_INT LEDs to the panel underside, route to a corner, then set the floor.
Pic 12–13, 2F wallsWire the EXT balcony light.
Pic 14, 2F ceiling✦ wire before glue Glue the 2 UP_INT bedroom LEDs to the panel underside before it goes down.
Pic 16–17, roofFix the UP_INT attic LED to a rafter before closing the roof; dormers double as light wells.
FinishRoute the power-bank charge port to a hidden opening (rear wall / chimney base). Leave a base access hatch.

Bill of materials

Arduino + LEDs already on hand (struck through)

Arduino Nano×1

Warm-white LEDs×12

ULN2803A driver (+ DIP socket)×1

220Ω resistors (150Ω to brighten)×14

Momentary pushbutton×1

Slide switch (master, in 5V line)×1

USB power bank · always-on mode×1

USB-A pigtail / breakout×1

Hookup wire 26–30 AWG (R/B/sig)~10m

Perfboard for driver board×1

Hot glue + sticks,

Heat-shrink / Kapton tape,

1000µF cap across 5V (optional)×1

Drill bits 1–1.5mm,

Tools: soldering iron + solder, wire strippers, flush cutters, multimeter (verify each zone before gluing it in).