LD2450 Mounting Guide

LD2450 Mounting Guide

Critical reading for v6.x. Single-sensor architecture has a real geometric requirement: the LD2450 must have line-of-sight to both arms of the LED run. Get this wrong and the system will show "lights stop in the middle of the strip and never come back" symptoms in your second arm.

The LD2450 in 30 seconds

• 24 GHz mmWave radar.
• Reports up to 3 simultaneous targets as (x_mm, y_mm, v_mm/s) plus per-target resolution.
• 60° horizontal cone, ~6 m max range.
• Effective range degrades with off-axis targets — a target at 4 m straight ahead is reliably detected; at 4 m and 30° off-axis it's marginal.
• Mounts behind plastic / acrylic (not metal). 24 GHz passes through most non-conductive materials.
• Vertical FOV is narrower than horizontal — mount at hip-to-shoulder height for adults.

The vantage-point principle

For v6.x to work with one sensor, the sensor must sit at a position where everywhere a person can be on the LED strip is inside its 60° cone.

This naturally puts the sensor at the inside corner of an L-shape and the centre-back of a U-shape.

Straight strip

Easy mode. Mount at one end of the strip, pointed along it.

flowchart LR
  S((LD2450)) -.->|covers| L1[LED 0]
  S -.->|covers| L2[LED 50]
  S -.->|covers| L3[LED 99]

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L-shape (the typical staircase)

Mount at the inside corner of the L, pointed across the corner so both arms are inside the 60° cone.

           Arm A (top flight)
        ┌─────────────────────
        │
        │
   inside
   corner ●  ← mount LD2450 here, facing into the corner
        │
        │
        │ Arm B (bottom flight)
        └─────────────────────

The sensor "sees" both arms because they meet at the inside corner where it's mounted. A target on Arm A appears at large +x / small y; on Arm B at small x / large +y. The future LED-engine 2-D zone mapping reads these and decides which segment to light up.

❌ Don't mount at the outside corner — the sensor sees the wall, not the LEDs. ❌ Don't mount at the top of Arm A — the bottom of Arm B is past the 60° cone. ✅ Do mount at the inside corner with the sensor's broadside facing into the L.

U-shape (a hallway with two corners)

Mount at the centre-back of the U, broadside facing the opening of the U.

   Arm A     centre     Arm C
  (left)    ●           (right)
            ↑
       LD2450 here, broadside facing
       outwards into the U opening
   Arm B
   (back wall, between arms A and C)

Both side-arms are inside the 60° cone. The bottom Arm B is the closest to the sensor.

For long U-shapes (>3 m arms), this gets tight — the side-arm far ends might fall outside the 60° cone. Range-test before locking position.

Asymmetric stairs (3-step landing + 12-step main flight)

Treat the inside corner of the landing as the mount point. The 3-step Arm A is short and entirely inside the cone; the 12-step Arm B is the long one — make sure its far end is still detected.

If your main flight is so long that detection drops at the top, two options:

• Move the sensor up to a higher mounting position so the cone reaches further.
• Accept the limit — the top few stairs go uncontrolled, with the strip falling to background lighting. In practice this is often fine because people pause at landings anyway.

Configurations that don't fit single-sensor

• T-junctions — 3 arms meeting at a point. The 60° cone can't see all 3.
• Stairs with a wall between flights — most apartment stairwells with a structural wall isolating top and bottom flights.
• Spiral staircases — geometry rotates beyond the cone.

For these, either stay on v6.0.0 (dual-device, on main) or open an issue describing your install — if multiple users need it, an optional second-sensor mode could land in a future v6.x release.

Mounting height

For a hallway, mount at hip-to-shoulder height (~80–140 cm from floor). The vertical FOV is narrower than horizontal; too low and your feet are outside the cone, too high and your head pokes out the top.

For staircases, height matters most for the inside-corner mount: aim the sensor's broadside roughly horizontally so its narrower vertical FOV catches the full height range of a person walking up/down.

The sensor itself is small (~3 × 3 cm PCB). It hides easily behind acrylic, fabric, or thin plastic. Do not mount behind metal — 24 GHz reflects.

Range testing before you lock the position

Before drilling holes / committing to wire runs, do this:

1. Power on the device and join Wi-Fi.
2. Open the web UI → Live tab. The distance number updates in real time.
3. Hold the sensor at the candidate mount position.
4. Walk the full length of each arm in turn. For each arm:
   • Walk slowly from near to far end.
   • Watch the distance number on the Live tab.
   • At what distance does the reading start to drop or jump erratically?
5. The arm's "reliable end" is roughly the distance where the reading stays stable.

If both arms have reliable detection across their full length, lock the position. If one arm drops detection partway, try:

• Tilting the sensor toward that arm (3–5° pitch makes a noticeable difference).
• Mounting closer to that arm (move 10–20 cm).
• Raising the mount height.

If no position works, the geometry is past single-sensor's limits. See "Configurations that don't fit" above.

Mounting hardware

The LD2450 has two M2 mounting holes. For a finished install:

• 3D-printed bracket — a simple flat plate with two M2 standoffs holds the sensor flat against the mount surface. STL files in the Assets/STL Files directory of the repo cover several geometries.
• Acrylic cover — 2–3 mm acrylic in front of the sensor is invisible at 24 GHz and protects from dust.
• Fabric cover — thin fabric (curtain weight) also passes 24 GHz cleanly.

Avoid:

• Metal covers (any thickness).
• Mounting against unpainted metal (acts as a reflector).
• Mounting next to a 2.4 GHz antenna (the C3's own Wi-Fi antenna is fine; the LD2450 operates at 24 GHz which is far from Wi-Fi's 2.4 GHz band, no interference).

After mounting

Open Hardware → Radar diagnostic in the web UI. The "last frame age" should stay under 200 ms; the byte / frame counters should climb steadily. If frame count is climbing but distance reads 0, check that "target_count" in the diagnostic JSON is non-zero when you stand in front of the sensor — if always 0, the radar is talking but not detecting.

If you need to tune detection sensitivity, the LD2450's gate sensitivity is configurable via its own UART command set. v6.x firmware doesn't currently expose this in the UI; if you want to tune, you'd flash the manufacturer's tool temporarily, configure, then re-flash AmbiSense.

See also

• Hardware Setup — wiring details
• Web UI Tour — where to see the radar diagnostic
• Troubleshooting — when distance never updates