Garage Construction Project

Rear & Side Security Lighting

15 min read

Overview

Rear and side garage walls each have two windows. Both walls sit close to neighboring property — the rear is a short distance from a fence, the side is only ~3 ft from a chain-link fence. Surveillance cameras were rejected for these elevations because their field of view would be 90% in the neighbor’s yard.

This design replaces the camera role with motion-activated wall packs for deterrence, plus independent per-zone HA notifications to substitute for the camera alert function the cameras would have provided. The architecture is engineered to put zero light into either neighbor’s yard.

Goals

  • Deter approach to the rear and side garage walls, especially overnight, without sending light over either property line.
  • Notify HA per-zone when motion is detected near a specific window, so notifications are actionable (“Rear-left window, 2:14am”) rather than generic.
  • No false triggers from neighbor pets, neighbor foot traffic, or environmental motion (foliage, heat shimmer).
  • Match the existing Shelly + Home Assistant control architecture used by the front soffit lights.

Constraints That Drove the Design

  • Chain-link fence at 3’ on the side wall is visually transparent; light leaking sideways or upward at this distance dumps directly onto the neighbor’s property. Fully-shielded fixtures are not optional here.
  • Standard wide-cone PIRs (100–360°) are unusable on these walls — half their detection lobe sits in the neighbor’s yard. Any cat, dog, or person on the neighbor’s side of the fence would trip the lights every night.
  • Cameras already rejected for these walls; sensor coverage is for deterrence + notification, not surveillance recording.

✅ DECIDED Architecture

Decision Date: 2026-05-02 Architecture: Curtain PIR per wall (Optex BXS-AM ×2, dual-curtain) drives fully-shielded wall packs (Lithonia OLWX1 13W ×4, one above each window) through a single Shelly Pro 4PM that exposes all 4 zones to Home Assistant as independent entities.

WallSensorRange setting (each side)Wall packsLighting zones
Rear (40’ wide)1× BXS-AM, center-mountedSetting 4 (~28 ft each side)2× OLWX1 13W above each window2 (rear-left, rear-right)
Side (24’ wide)1× BXS-AM, center-mountedSetting 3 (~20 ft each side)2× OLWX1 13W above each window2 (side-north, side-south)

All four zones (sensor inputs + light outputs) terminate at a single Shelly Pro 4PM in a small DIN-rail enclosure near the rear-side corner of the garage.

Why These Components

Optex BXS-AM (curtain PIR with anti-masking)

  • Curtain detection plane (not a cone) — runs flat along the garage wall, parallel to the ground. The neighbor’s yard is geometrically excluded from the detection volume because it’s not in the plane.
  • Independent left/right alarm outputs. One BXS-AM = two distinct dry-contact outputs, each separately adjustable for range (5 steps: 2.5/3.5/6/8.5/12 m) and sensitivity. So 2× BXS-AM = 4 zones, matching the 4 windows 1:1.
  • Anti-masking and pet immunity. Ignores cats, foxes, birds, sunlight reflections, AC unit waste heat, vegetation sway. Tampering attempts (paint, tape) trigger a separate tamper signal.
  • Dual technology not required. The BXS-AM is dual-PIR; the geometry of a curtain plane plus the digital filtering eliminates the false-trigger sources that drive most installs to PIR+microwave.

Lithonia OLWX1 13W LED wall pack

  • Full cutoff — zero uplight, zero side-spill above the horizontal. Light is emitted only downward in a controlled distribution.
  • Low output (1,300 lm) — bright enough to wash the wall and 6–8 ft of ground for deterrent and camera-quality use, dim enough that even diffuse reflection off the wall isn’t an issue at the property line.
  • Bronze low-profile housing — visually unobtrusive on the side wall where the chain-link fence offers no privacy buffer.
  • Cheap, widely stocked at Home Depot. ~$50–60 each.
  • Photocell-equipped variant is preferred — gives a hard-floor “never on during daytime” gate, on top of HA’s logic.

Shelly Pro 4PM (DIN-rail input/output controller)

  • 4 dry-contact inputs + 4 16A relay outputs in a single device. All 4 sensor zones and all 4 light zones live in one box.
  • Local-first. Even with HA or Wi-Fi down, sensor → light is hard-mapped at the device level.
  • Per-output power monitoring — per-zone kWh data for verifying lights aren’t stuck on.
  • Native HA integration via Shelly integration (or MQTT). Each input becomes a binary_sensor, each output a switch.

Per-Wall Configuration Detail

Rear wall (40’ total)

  • BXS-AM mounting: centered on the wall at ~8 ft height, just under the soffit.
  • Range: Setting 4 (8.5 m / 28 ft) on both L and R.
    • Covers ~4 ft past each rear corner — adequate overlap, no detection past the corners into yard areas you don’t care about.
  • Sensitivity: Medium on both sides (default for this range).
  • Wall packs: OLWX1 13W ×2, mounted directly above each window at ~9 ft height, aimed straight down.

Side wall (24’ total)

  • BXS-AM mounting: centered on the wall at ~8 ft height, just under the soffit.
  • Range: Setting 3 (6 m / 20 ft) on both L and R.
    • Covers ~4 ft past each side corner.
  • Sensitivity: Medium-low on the fence side, medium on the other side.
    • The chain-link is 3 ft away — the curtain plane already excludes the neighbor’s yard geometrically, but lower sensitivity gives a second layer of immunity.
  • Wall packs: OLWX1 13W ×2, mounted directly above each window at ~9 ft height, aimed straight down.

Low-Voltage Control Cabinet

The Shelly Pro 4PM, 12V PSU, terminal blocks, and any future 12V/control devices live in a dedicated low-voltage control cabinet mounted on the wall adjacent to the main 200A panel (or wherever the smurf-tube routing converges). This cabinet becomes the long-term smart-home / low-voltage hub for the building.

Why not in the main breaker box

The main 200A residential load center is listed as a branch-circuit distribution panel. Adding non-distribution equipment (PSUs, signal cabling, smart relays beyond simple in-box Shelly modules) violates the panel’s UL listing — regardless of whether the wires can be physically separated. Inspectors flag this on listing grounds. A purpose-built NEMA control enclosure is the right home.

NEC 725.136 compliance for mixed-voltage cabinets

Class 1 (line voltage) and Class 2 (low-voltage signal) circuits may share a control enclosure when:

  • They terminate at listed equipment designed for combined use (the Shelly Pro 4PM and HDR-15-12 are both UL-listed for this), AND
  • Wiring inside the enclosure maintains 0.25” minimum physical separation between Class 1 and Class 2 conductors (NEC 725.136(D)), or a partition is used.

In practice this is achieved with standard control-panel construction:

  • Separate gland plates / knockouts for line voltage and low voltage (typically opposite sides of the cabinet).
  • Slotted wireway duct (Panduit / Wago / generic) along one side for line voltage, another side for low voltage.
  • No parallel runs of Class 1 and Class 2 conductors within 0.25” of each other.
  • The line-voltage feeds and low-voltage signals only converge at the Shelly’s terminals — which is permitted because the Shelly is listed for that combined use, with internal separation between its 120V relay sections and dry-contact input sections.

This is textbook industrial / commercial control-panel practice, not a gray area.

Cabinet sizing

Don’t size the cabinet to today’s needs (5 DIN slots: 1 for HDR-15-12 + 4 for Shelly Pro 4PM). Size for the 10-year vision:

Future deviceDIN slots
Shelly Pro 4PM (current)4
HDR-15-12 (current 12V PSU)1
Shelly Plus i4 — front motion PIR (Lighting)1
Future 24V PSU (door strikes, industrial sensors)1–2
ESPHome ESP32 boards on DIN adapters1–2 each
12V terminal blocks (5–10 pairs)2–3
Fuse block (Class 2 distribution)1
Future Shelly Pro 3EM (energy monitoring)4
DIN-rail GbE network switch (if going that route)2–3

Target: 24-module enclosure (2× 12-module rows), NEMA 1, hinged door, US-stocked. Reserve ~75% empty on day one.

Internal layout

                ┌────────────── LV CABINET (NEMA 1) ──────────────┐
                │                                                  │
   120V in ────►│ ◄── line-voltage gland plate (LEFT side)        │
   (15A from    │     [slotted wireway duct, line side]           │
    main panel) │                                                  │
                │  ┌─────────── DIN rail (top row) ────────────┐  │
                │  │ HDR-15-12 │ Shelly Pro 4PM │ (reserved)   │  │
                │  └───────────┴────────────────┴─────────────┘  │
                │  ┌─────────── DIN rail (bottom row) ─────────┐  │
                │  │ Fuse block │ 12V terminals │ (reserved)   │  │
                │  └────────────┴───────────────┴─────────────┘  │
                │                                                  │
                │     [slotted wireway duct, signal side]          │
   12V out ────►│ ◄── low-voltage gland plate (RIGHT side)        │
   to BXS-AMs   │                                                  │
   Sensor in ──►│                                                  │
   from BXS-AMs │                                                  │
                └──────────────────────────────────────────────────┘

Bill of Materials

ItemQtyUnitTotalSource
Optex BXS-AM2$206$412JMAC
Lithonia OLWX1 LED 13W 4000K w/ photocell4~$60$240Home Depot
Shelly Pro 4PM1$130$130shelly.com or Amazon
Mean Well HDR-15-12 (12V 1.25A DIN PSU)1$12$12Bravo Electro
NEMA 1 control cabinet, ~24-module, hinged door1$100–150$125Hammond / Schneider / electrical supply
TS35 DIN rail (300mm × 2 segments)2$1.55$3Bravo Electro
Slotted wireway duct (1” × 2”, ~6 ft total)1$25$25Amazon / electrical supply
12V terminal block (DIN-mount, ≥10 pairs)1$15$15Amazon
Class 2 fuse block (DIN-mount, 4–6 position)1$20$20Amazon
14/2 MC cable for fixture power leads (~120 ft, accounts for runs from central cabinet)1$80$80Home Depot
22/4 shielded sensor cable (~120 ft)1$50$50Amazon (alarm cable)
Weatherproof junction boxes (4×4 with cover)4$8$32Home Depot
Misc — strain reliefs, sealant, screws, conduit, ferrules, labels——$50Home Depot
TOTAL — materials only~$1,094

Cable footage is up from the original ~80 ft estimate because runs are now from the central LV cabinet (rather than a corner junction) — the smurf tubes carry the runs but cable length still counts. About $50 of the increase is cable; the rest is the larger cabinet, wireway, and accessories that future-proof the install.

DIY vs. professional install

  • DIY install: materials only (~$1,094), 2 days of work (run cable through smurf tubes, mount cabinet + fixtures + sensors, terminate, configure Shelly + HA).
  • Professional install: add ~2,300–2,900 total.

Circuit Requirements

Adds to Electrical Planning:

  • One new 15A 120V circuit dedicated to the LV cabinet (which then distributes to the rear/side security lighting + sensor power).
    • Total connected load: 4× 13W wall packs + 1× Shelly Pro 4PM + 1× HDR-15-12 + 2× BXS-AM ≈ 60–70W. The dedicated breaker is for fault isolation and future-expansion headroom, not amp capacity.
    • “Always on” for sensor power means a fault here shouldn’t take out other lighting.
  • Cable routing rough-in (during stage 3 framing/electrical):
    • Home run from main panel to the LV cabinet location (adjacent to the panel or at the smurf-tube convergence point) — short run via EMT or ENT.
    • From the LV cabinet, branch via the smurf-tube infrastructure:
      • 14/2 MC to each of the 4 wall pack locations (above each rear/side window).
      • 22/4 shielded alarm cable to each of the 2 BXS-AM center-mount locations (one per wall).

This circuit was not in the original Electrical Planning doc — it is being added now.

Wiring Topology

MAIN 200A PANEL ─15A breaker─▶ [LV CABINET (adjacent to panel)]
                                        │
                                        │  ┌─ HDR-15-12 (12V PSU)
                                        │  ├─ Shelly Pro 4PM
                                        │  ├─ Class 2 fuse block
                                        │  └─ 12V terminal blocks
                                        │
                                        │  Line-voltage outputs (via smurf tubes):
                                        ├─14/2 ▶ Wall pack: rear-left
                                        ├─14/2 ▶ Wall pack: rear-right
                                        ├─14/2 ▶ Wall pack: side-north
                                        └─14/2 ▶ Wall pack: side-south
                                        
                                        Low-voltage I/O (via smurf tubes):
                                        ├─22/4 shielded ▶ BXS-AM (rear, center-mount)
                                        │                    │ 12V+ ◄── HDR-15-12
                                        │                    │ GND  ──── common
                                        │                    │ Alarm L ──▶ Shelly input 1
                                        │                    │ Alarm R ──▶ Shelly input 2
                                        │                    └ Tamper ──▶ Shelly input (aux)
                                        │
                                        └─22/4 shielded ▶ BXS-AM (side, center-mount)
                                                             │ 12V+ ◄── HDR-15-12
                                                             │ GND  ──── common
                                                             │ Alarm L ──▶ Shelly input 3
                                                             │ Alarm R ──▶ Shelly input 4
                                                             └ Tamper ──▶ Shelly input (aux)

NEC compliance recap

  • The Shelly Pro 4PM is UL-listed equipment whose 120V relay terminals and Class 2 dry-contact input terminals are designed for combined use on a single device chassis — co-locating them in one cabinet is permitted by NEC 725.136(D).
  • Inside the cabinet, line-voltage conductors enter on one side (left), low-voltage conductors enter on the other (right), with slotted wireway duct on each side keeping them ≥0.25” apart.
  • The HDR-15-12 has line voltage on its input and Class 2 on its output — internal to the listed device.
  • Result: a fully code-compliant mixed-voltage control cabinet, built to standard control-panel practice.

Home Assistant Integration

Entities exposed (one each per zone)

  • binary_sensor.garage_rear_left_pir
  • binary_sensor.garage_rear_right_pir
  • binary_sensor.garage_side_north_pir
  • binary_sensor.garage_side_south_pir
  • switch.garage_rear_left_wallpack
  • switch.garage_rear_right_wallpack
  • switch.garage_side_north_wallpack
  • switch.garage_side_south_wallpack

Automation outline

# 1. Per-zone targeted lighting (most deterrent, least neighbor-impact)
- trigger: PIR zone X tripped
  conditions: sun.below_horizon
  action:
    - turn on wallpack X
    - wait 3 minutes after last motion
    - turn off wallpack X
 
# 2. Notification per zone
- trigger: PIR zone X tripped
  conditions: time between 23:00 and 06:00
  action:
    - notify mobile app: "Garage motion: zone X at {{ now }}"
 
# 3. Pattern escalation
- trigger: 2+ zones tripped within 60 seconds, between 23:00–06:00
  action:
    - notify mobile app HIGH PRIORITY
    - record front-door cameras for 2 minutes (already-existing BlueIris setup)
    - turn on all 4 wall packs
 
# 4. Daytime: log only
- trigger: any PIR
  conditions: sun.above_horizon
  action: (none — entity history captures it)
 
# 5. Tamper
- trigger: any tamper input
  action: notify mobile app immediately, regardless of time

Why per-zone matters

  • Targeted lighting is more deterrent (subject perceives a specific reaction to them, not generic light) and reduces neighbor light pollution further (only one wall pack on, not all four).
  • Granular notifications filter signal from noise — “Side-south motion at 3:14am” is actionable; “Garage motion” gets ignored after the third false alert.
  • Pattern detection (multiple zones in sequence) is much higher confidence than a single zone, justifying louder alerts.

Why the Front Wall Uses a Different Architecture

The front of the garage faces the driveway and street with no close fence. The constraint that drove curtain-PIR + full-cutoff selection here doesn’t apply. The front:

  • Is already covered by surveillance cameras (Amcrest IP8M corner cameras + Reolink doorbell, all into Blue Iris with planned CodeProject.AI — see homelab project).
  • Already has soffit lights with a smart relay installed (Shelly 1PM Mini Gen 4 behind the entry switch, Lighting).
  • Benefits from earlier and wider detection — the priority is to light the area as someone enters the camera frame, so day-mode capture is used during the approach rather than night mode.

The front motion-sensor architecture (RAB STL360 PIR routed to a Shelly Plus i4 in this same LV cabinet, HA orchestrating the existing soffit Shelly relay) is documented at Front Motion Sensor and 2026-05-02 — Front Motion Sensor Architecture.

Action Items

Procurement (stage 5)

  • Order 2× Optex BXS-AM from JMAC. — order:: Exterior Lighting Order — stage:: 5
  • Order 4× Lithonia OLWX1 13W 4000K w/ photocell from Home Depot. — order:: Exterior Lighting Order — stage:: 5
  • Order Shelly Pro 4PM. — order:: Exterior Lighting Order — stage:: 5
  • Order Mean Well HDR-15-12 (12V PSU) from Bravo Electro. — order:: Exterior Lighting Order — stage:: 5
  • Order 24-module NEMA 1 control cabinet (hinged door), DIN rail (2× 300mm), slotted wireway duct, 12V terminal blocks, Class 2 fuse block. — order:: Exterior Lighting Order — stage:: 5
  • Order 22/4 shielded alarm cable (~150 ft spool) and 14/2 MC cable as needed. — stage:: 5

Pre-drywall electrical rough-in (stage 3)

  • Determine LV cabinet location — adjacent to main 200A panel or at smurf-tube convergence point. — stage:: 3
  • Mount LV cabinet backing board (¾” plywood) at chosen location. — stage:: 3
  • Pull 14/2 home run from main panel to LV cabinet location (short EMT/ENT run). — stage:: 3
  • Pull 14/2 from LV cabinet through smurf tubes to each of 4 wall pack locations. — stage:: 3
  • Pull 22/4 shielded from LV cabinet through smurf tubes to each of 2 BXS-AM center-mount locations. — stage:: 3
  • Add new 15A breaker assignment to Electrical Planning circuit schedule. — stage:: 3

LV cabinet build (stage 6)

  • Mount LV cabinet to backing board; install DIN rails and slotted wireway duct (line-voltage side and signal side separately). — stage:: 6
  • Install HDR-15-12, Shelly Pro 4PM, fuse block, and 12V terminal blocks on DIN rails. — stage:: 6
  • Land 120V feed on Shelly Pro 4PM and HDR-15-12 inputs; route through line-voltage wireway only. — stage:: 6
  • Land 14/2 wall pack feeds on Shelly Pro 4PM relay outputs; route through line-voltage wireway. — stage:: 6
  • Land 22/4 sensor cables on 12V terminal blocks (power) and Shelly inputs (signal); route through signal wireway only. — stage:: 6
  • Verify ≥0.25” separation between Class 1 and Class 2 conductors throughout cabinet. — stage:: 6
  • Label every terminal point and cable per the wiring topology diagram. — stage:: 6

Install & commission (stage 6)

  • Mount 4× wall packs above windows; aim straight down; verify no horizontal spill at fence line. — stage:: 6
  • Mount 2× BXS-AM center on each wall; configure DIP switches for range/sensitivity per the per-wall config above. — stage:: 6
  • Energize circuit; commission Shelly Pro 4PM via Shelly app. — stage:: 6
  • Add Shelly Pro 4PM to Home Assistant; rename entities to match the zone names above. — stage:: 6
  • Implement HA automations per the outline above; tune timing windows over first week. — stage:: 6

Post-install verification (stage 7)

  • Walk the property line at night for 1 week — log any false triggers from neighbor activity, adjust sensitivity if needed. — stage:: 7
  • Verify no light is visible from inside the neighbors’ windows or yards. — stage:: 7

References

Product datasheets

Graph View

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