qlc-moving-head

name: qlc-moving-head description: > Program moving head fixtures in QLC+ — covers 16-bit pan/tilt DMX addressing, degree-to-DMX conversion, and phantom sweep chaser patterns. Channel layouts shown are for the Hero Spot Wash 140; use query_fixture_channels to discover channels for other fixtures. USE FOR: pan/tilt positioning, moving head scenes, phantom sweep, chaser with blackout reset, beat-synced chasers, Hero Spot Wash fixture programming. DO NOT USE FOR: wash-only fixtures, LED strip effects, ISF shaders. metadata: author: André Bossard version: "1.0"

QLC+ Moving Head Programming

16-Bit Pan/Tilt Addressing

Moving heads use two DMX channels per axis for 16-bit precision:

• Coarse channel (MSB) = high byte, controls broad positioning
• Fine channel (LSB) = low byte, controls micro-adjustment

Conversion formulas

Degrees → DMX (coarse + fine):

dmx_16bit = degrees / max_degrees × 65535
coarse = dmx_16bit ÷ 256  (integer part)
fine   = dmx_16bit mod 256

DMX → Degrees:

dmx_16bit = coarse × 256 + fine
degrees = dmx_16bit / 65535 × max_degrees

Hero Spot Wash 140 specifics

Base position (180°/180° = straight into room):

• Pan: coarse 85, fine 85 (16-bit: 21845)
• Tilt: coarse 242, fine 133 (16-bit: 62085)

Common pan positions around 180° center

Channel 4: Pan/Tilt Speed

• 0 = maximum motor speed (fastest snap)
• 255 = slowest motor speed
• For phantom effects, always use 0 (max speed) so the head returns as fast as possible during blackout.

Phantom Sweep Pattern

A phantom sweep creates the illusion of one-directional beam movement by blacking out during the return trip.

How it works

[LEFT ON] ──3-beat fade──▶ [RIGHT ON] ──instant──▶ [BLACKOUT + snap back] ──▶ loop
   beam visible, sweeping right         beam off, motor returns to left

Required scenes (3)

1. Phantom Left On — beam at left position, spot dimmer 255
2. Phantom Right On — beam at right position, spot dimmer 255
3. Phantom Blackout Reset — beam at left position, spot dimmer 0

All scenes must include:

• Both coarse AND fine channels for pan and tilt
• pt_speed = 0 (max motor speed)
• wash_dim = 0 (spot only)
• Consistent tilt across all steps

Scenes are created with explicit channelValues — each entry is {fixtureID, channel, value}. Use query_fixture_channels to discover channel indices for your fixture.

Chaser configuration

• Run order: loop
• Tempo type: beats (syncs to BPM)
• Total loop: 4 beats

Key design decisions

1. Narrow the sweep range — ±20° (not ±40°) reduces motor travel distance, enabling shorter blackout holds.

2. Spot dimmer must be LTP — by default, QLC+ treats dimmer channels as HTP (Highest Takes Precedence). The blackout scene's dim=0 will be overridden by dim=255 from adjacent steps. Change spot_dim (ch 5) precedence to LTP via configure_channels.

3. No dimmer fades on return — ramping the dimmer up during the snap-back looks broken. Use instant on/off only.

4. Beat sync vs time — beat mode automatically scales the sweep speed with BPM. At 120 BPM: 3 beats = 1.5s sweep, 1 beat = 500ms blackout. At 170 BPM: 3 beats = 1.06s sweep, 1 beat = 353ms blackout (tight but workable with ±20° range at max motor speed).

Common tilt positions

Layer Architecture

Split channels into two independent layers so movement and look can be swapped independently.

Movement Layer (MV:)

Owns: pan (0,1), tilt (2,3), pt_speed (4), spot_dim (5)

Controls position and on/off. The dimmer lives here (not in the look layer) so the phantom chaser can black out the beam without HTP conflicts.

Look Layer (LK:)

Owns: color_wheel (7), gobo (8), gobo_wheel (9), gobo_rot (10), focus (11), prism (12)

Controls beam appearance only. No pan/tilt, no dimmer.

Why dimmer belongs to movement, not look

• Dimmer must be LTP (set via configure_channels) so the chaser's dim=0 actually wins
• If both layers set dimmer, they fight — keep ownership exclusive
• Strobe channel for blackout is unreliable (fixture-specific values, not always a clean close)

Usage pattern: Collections

Combine one MV chaser + one LK scene in a QLC+ Collection. This lets you:

• Swap looks without stopping movement
• Swap movement patterns without changing the look
• Pre-build every combo (movement × color) as a one-click trigger

Tilt Phantom Sweep

Same phantom principle applied to the tilt axis — beam sweeps vertically then snaps back in blackout.

Tested beat ratios

Recommended tilt range

• 170° → 100° (70° travel) works well for dramatic vertical sweeps
• Shorter ranges (e.g. 180° → 130°) need less blackout time but less visual impact
• At max motor speed (pt_speed=0), 2 beats at 120 BPM (1s) is enough for 70° return

Variations

• Reverse phantom: swap start/end scenes — beam appears to move in opposite direction
• Pan phantom: same pattern on pan axis (±20° around 180° center, 3/1 beat ratio)
• Diagonal: vary both pan and tilt across steps
• Multiple speeds: create Fast/Mid/Slow chasers sharing the same position scenes, only differing in beat ratios